Search Calculators

Roman Numeral Converter

Convert between Arabic and Roman numerals.

IP Subnet Calculator

Compute network, broadcast and usable hosts from an IPv4 address and prefix.

Password Generator

Generate a strong password from settings and estimate its entropy.

Base64 Encoder / Decoder

Encode text to Base64 or decode Base64 back to text.

URL Encode / Decode

Encode text to percent-encoding (%XX) or decode it back.

Sleep Calculator

Estimate a recommended bedtime from your wake time and sleep cycles.

Love Calculator

Enter two names to get a fun compatibility percentage.

Hong Kong Salaries Tax & MPF Calculator

Estimate mandatory MPF contributions, salaries tax payable and net income.

BMI and Calorie Calculator

Calculate BMI and daily calorie needs.

Compound Interest Calculator

Calculate compound interest growth: enter the initial principal and monthly contribution to estimate the future value, cumulative interest and contributions.

Simple Interest Calculator

Calculate the interest and maturity value generated on a principal at simple interest.

Savings Goal Calculator

Work out how much to save each month to reach your savings goal.

Fixed Deposit Calculator

Calculate the maturity value of a Hong Kong dollar time (fixed) deposit.

Personal Loan Calculator

Calculate personal loan monthly repayment, total interest and total payment.

Investment Return Calculator

Calculate the total return and annualised (CAGR) return on an investment.

Inflation Calculator

See how inflation erodes purchasing power and raises the future amount needed.

Retirement Savings Calculator

Project your retirement savings and the monthly saving required.

Rent vs Buy Calculator

Compare the total cost of renting versus buying over a holding period.

CAGR Calculator

Calculate the Compound Annual Growth Rate (CAGR) over a period.

APY Calculator

Convert a nominal annual rate and compounding frequency into the real annual yield (APY).

Future Value Calculator

Compute the future value (FV) of a present sum under compound interest.

Present Value Calculator

Discount a future lump sum back to its present value (PV) today.

Asset Appreciation Calculator

Estimate the future value and total gain of an asset growing at a constant annual rate over a number of years.

Net Present Value (NPV) Calculator

Discount each period's cash flow to compute the Net Present Value (NPV) of an investment project.

Rate of Return Calculator

From the initial value, final value and income received, compute the total rate of return (ROR) and profit/loss of an investment.

Holding Period Return Calculator

Combine capital gain and dividend income to compute the holding period return (HPR) of a stock, splitting it into price gain and dividend yield.

Real Rate of Return Calculator

Adjust a nominal return for inflation to compute the real rate of return (purchasing-power return).

Time Value of Money (TVM) Calculator

Compute the present value or future value including regular contributions (end-of-period annuity).

Internal Rate of Return (IRR) Calculator

Find the discount rate that zeroes the NPV to compute an investment's internal rate of return.

Discounted Cash Flow (DCF) Valuation Calculator

Forecast annual free cash flows, a discount rate and a terminal growth rate, then compute the enterprise value via discounting.

Effective Annual Rate (EAR) Calculator

Convert a nominal annual rate and compounding frequency into the real Effective Annual Rate (EAR).

Continuous Compound Interest Calculator

Using FV = P·e^(rt), compute the future value, interest and equivalent effective annual rate under continuous compounding.

Perpetuity Calculator

Calculate the present value of a perpetual periodic payment (with or without growth).

Sharpe Ratio Calculator

Divide the excess return (portfolio return minus the risk-free rate) by total risk (standard deviation) to measure a fund's risk-adjusted return.

Sinking Fund Calculator

Work out the fixed periodic deposit needed to accumulate a target amount after a number of periods.

Compute the present value factor of an ordinary annuity paying 1 per period, and the resulting annuity present value.

Expected Return Calculator

Compute the expected return as the probability-weighted average of up to five scenarios.

Modified IRR Calculator

From the cash flows, a safe (finance) rate and a reinvest rate, compute the modified internal rate of return (MIRR).

Annualized Rate of Return Calculator

Convert a return earned over a period other than one year into an equivalent annual rate for fair comparison.

Capital Gains Yield Calculator

Compute the capital gains yield — the price appreciation component of an investment's total return.

Compound Growth Calculator

From initial principal, annual rate, years, frequency and contributions, compute the future value and total compounded growth.

Expense Ratio Calculator

Compute the cumulative cost of a fund's expense ratio eroding long-term returns.

Interest Rate Calculator

Back-solve the deposit rate from principal, final balance, term and compounding frequency.

Compute the future balance, principal contributed, and accumulated interest of a money market account with regular deposits.

Compound Interest Rate Calculator

From principal, final balance and years, solve the compound annual rate (with continuous compounding supported).

Effective Annual Yield Calculator

From bond face value, annual coupon and payment frequency, compute the coupon rate and effective annual yield.

Percentage Return Calculator

Calculate the total percentage return and the (geometric) annualised return of an investment.

Compute the percentage change between two years, and the compound annual growth rate (CAGR) over multiple years.

Certificate of Deposit (CD) Calculator

From principal, annual rate, term and compounding frequency, compute the CD maturity balance and interest earned.

Discount Rate Calculator

Back out the implied annual discount rate from present value, future value, periods and compounding frequency.

Effective Interest Rate Calculator

From the nominal annual rate and compounding frequency, compute the effective interest rate (EIR) and the periodic rate.

Equivalent Rate Calculator

Convert a nominal annual rate from one compounding frequency to another's equivalent rate, and compute the AER.

Opportunity Cost Calculator

See the after-tax gain and the inflation-adjusted real value you give up by spending a sum now instead of investing it.

Investment Calculator

Compute the future value, total principal and gains of a lump sum plus recurring contributions under compound interest.

Investment Fee Calculator

See how sales load, operating fee, turnover cost and redemption fee erode fund returns vs a zero-fee scenario.

From the initial deposit, final balance, years, and compounding frequency, reverse out the annual nominal rate a savings account must earn.

Basis Point Calculator

Convert a number of basis points into a percentage, a decimal and the actual dollar amount it represents.

Mutual Fund Calculator

Estimate a mutual fund's maturity value, total contributed and gains with compounding, using a monthly SIP or a one-off lump-sum investment.

Compute the week-over-week percentage change, absolute change, and compounded weekly growth rate between two values a given number of weeks apart.

Moving Average Calculator

Compute the simple moving average (SMA) sliding-window sequence for up to 6 price points at a chosen window length.

Convert between a lease money factor and the equivalent annual percentage rate (APR), using the conventional divisor of 2400.

Margin Interest Calculator

Compute the simple interest on a broker margin loan, using a 360-day year basis.

Maximum Drawdown Calculator

Compute the maximum drawdown from a peak to its subsequent low, plus the gain needed to recover and the recovery years.

Sortino Ratio Calculator

Measure risk-adjusted return using downside risk only: Sortino = (asset return − risk-free rate) ÷ downside deviation, which ignores upside volatility.

Measure risk-adjusted return by systematic risk (beta): Treynor = (portfolio return − risk-free rate) ÷ beta.

Information Ratio Calculator

Measure active management performance: Information Ratio = (portfolio return − benchmark return) ÷ tracking error.

Jensen's Alpha Calculator

Using CAPM, measure excess return: Alpha = portfolio return − [Rf + beta × (Rm − Rf)].

NOPAT Calculator

Compute NOPAT: net operating profit after tax = operating income × (1 − effective tax rate).

Compute MVA: market value added equals the current market value minus the capital invested.

Compute ROCE: return on capital employed = EBIT ÷ capital employed (total assets minus current liabilities).

TTM Calculator

Sum the last four quarters to get the TTM figure, and optionally compute the TTM P/E from the share price (using EPS inputs).

Hedge Ratio Calculator

Compute the hedge ratio: hedge position ÷ total exposure — how much of the portfolio's market risk is already covered by hedging.

Optimal Hedge Ratio Calculator

Compute the optimal hedge ratio = correlation × (spot price SD ÷ futures price SD), the share of exposure to hedge with futures.

Bitcoin ETF (Total Cost) Calculator

From amount, expected return and expense ratio, see the effective annual return, future value and total cost of holding a Bitcoin ETF.

Expected Utility Calculator

With the utility function U(x)=√x, compute the expected utility of two uncertain outcomes: EU = Σ probability × √amount.

Using the parametric method, compute Value at Risk: VaR = |expected return − z-score × √days × standard deviation| × portfolio value.

50/30/20 Budget Rule Calculator

Split after-tax income into 50% needs, 30% wants and 20% saving/debt, to build a personal budget quickly.

Emergency Fund Calculator

Multiply monthly essential expenses by the target months to work out how much emergency reserve to set aside.

Net Worth Calculator

Net worth = total assets minus total liabilities. Take stock of your finances in one view.

Savings Calculator

Estimate the final balance, principal and interest of savings under compounding and regular contributions.

Monthly Budget Calculator

From monthly income and core expenses, compute total spending and the savings rate to check if your budget balances.

Car Loan Calculator

From the car price, down payment, trade-in, rate and term, compute the loan amount, monthly payment and total interest.

Car Loan Interest Calculator

From the loan amount, annual rate and term, compute the equal-monthly-instalment payment and total interest.

Car Affordability Calculator

From your monthly payment budget, rate, term, cash and trade-in, work back to the maximum car price you can finance.

Car Depreciation Calculator

From the initial value and age, estimate the current resale value, total depreciation and the cumulative depreciation percentage.

Car Lease Calculator

From MSRP, selling price, fees, residual and money factor, compute the monthly lease payment (depreciation + finance charge).

70/20/10 Budget Rule Calculator

Split after-tax monthly income automatically: 70% needs, 20% saving & debt, 10% lifestyle / giving.

Boat (Yacht) Loan Calculator

From boat price, down payment, rate and term, compute the loan amount, monthly payment and total interest — then weigh down payment vs term.

Simple Savings Calculator

Work out the simple-interest interest and maturity value of a deposit over a term.

Mobile Plan Comparison Calculator

Compare two mobile plans' total contract cost and monthly average to find the cheaper one.

Add up your monthly subscription costs across categories and estimate the annual spend and the annual waste from services you rarely use.

FIRE Calculator

Use the 4% rule to compute the assets needed for financial independence, and estimate years to reach it by current saving.

Millionaire Calculator

How long until your savings hit one million, given your current amount, monthly contribution and annual return.

Lifetime Earnings Calculator

From current age, retirement age, current salary and annual raise, estimate total lifetime earnings.

Wedding Budget Calculator

Split a total wedding budget by the usual industry shares into categories, and work out the average cost per guest.

From an initial principal and a fixed monthly contribution, compute the future savings value, principal contributed, and interest earned with compounding.

Gold Melt Value Calculator

From weight, purity (karat) and gold price, compute the pure-gold weight and melt value — the metal-only worth without brand or craft.

From the weight, purity, and silver price, compute the pure silver weight and the melt value of a silver item.

Scrap Gold Calculator

From the weight, purity and gold price, estimate the pure gold weight and the recyclable (scrap) value.

Scrap Silver Calculator

From the weight, purity and silver price, estimate the pure silver weight and the recyclable (scrap) value.

Dream Come True Calculator

Set your dream price, current savings, expected annual rate and plan months to work out the monthly saving needed, and see how principal, contributions and interest compose the goal.

Long Term Care Cost Calculator

Project the first-year and total long-term care cost (nursing home, home care) with annual inflation.

Sabbatical Savings Calculator

Work out how much to save before a sabbatical (career break): cover expenses, a safety buffer and income during the break.

Use the replacement-cost method to value housework, caregiving, and other unpaid labour as weekly, annual, and cumulative monetary worth.

Average Propensity to Consume (APC) Calculator

From total consumption and disposable income, compute the average propensity to consume (APC), average propensity to save (APS) and amount saved.

Bank Reconciliation Calculator

Adjust the bank and book balances for outstanding items to confirm both adjusted balances match (difference = 0).

Lottery Annuity Payout Calculator

Split the advertised jackpot into 30 growing annual payments to see the first, last and total payout.

Powerball Payout Calculator

Compare the after-tax cash lump sum with the after-tax 30-year annuity for a Powerball jackpot using a single combined tax rate.

Mega Millions Payout Calculator

Compare the lump-sum cash option with the 30-year annuity for a Mega Millions jackpot, with tax rough estimates.

Fit a log-normal distribution using the median and 90th-percentile anchors to estimate your income percentile within a population.

Down Payment Calculator

From the property price and down-payment ratio, instantly work out the cash deposit you need and the mortgage loan to borrow from the bank.

Capitalization Rate (Cap Rate) Calculator

Estimate a property's cap rate and implied value from net operating income and market value.

Loan-to-Value (LTV) Calculator

Compute the mortgage loan-to-value ratio from loan amount and property value, and the required down payment.

Divide a property's total price by its area to get the price per square foot (or per square meter) for easy comparison across listings.

Gross Rent Multiplier Calculator

From property price and annual gross rent, compute the gross rent multiplier (GRM) — how many years of rent equal the price, to quickly gauge value.

Occupancy Rate Calculator

Enter the occupied units and total units to get the occupancy rate and the vacancy rate, assessing a property or hotel's letting performance.

Real Estate Agent Commission Calculator

Enter the property sale price and the commission rate to compute the agent commission and the seller's net proceeds after commission.

Enter the monthly rent and commission rate (as a percentage of one month's rent) to compute the rental agency commission and how many months of rent it equals.

3x Rent Income Rule Calculator

From the monthly rent and a multiple, work out the required gross monthly and annual income, split across tenants.

Earnest Money Calculator

Enter the property price and earnest-money percentage to compute the deposit payable, and the remaining down payment after deducting it.

Enter your monthly income and target rent to find the affordable rent cap, the rent-to-income ratio, and the monthly and annual income needed to pay the target rent.

Enter the current rent and the increase percentage to compute the new rent, the monthly increase, and the extra rent paid over a year.

From the property's fair market value, repair costs, desired discount, and desired profit, estimate a reasonable offer price.

Debt-to-Income (DTI) Ratio Calculator

From gross monthly income and monthly debt payments, compute DTI and the allowable debt ceiling and borrowing headroom.

Credit Utilization Calculator

From total used and total credit limit, compute the credit utilization rate and the remaining available credit.

28/36 Rule Calculator

From monthly income, housing costs and other debts, work out the front-end ratio (28%) and back-end ratio (36%) to judge whether your mortgage and debt burden is healthy.

Finance Charge Calculator

From the carried balance, APR and billing-cycle days, compute one cycle's finance charge (interest) and the next opening balance.

Interest Per Day Calculator

Enter a loan or deposit balance and the annual rate to compute the daily rate and daily interest accrued.

Credit Card Minimum Payment Calculator

From balance, minimum-payment percentage, APR and floor, compute the required minimum payment (two common methods).

Debt Snowball Calculator

Simulate the snowball method: pay minimums on all, then throw the surplus at the smallest-balance debt first — build momentum.

Debt Avalanche Calculator

Simulate the avalanche method: pay minimums on all, then throw the surplus at the highest-rate debt first — minimise total interest.

Credit Card Payoff Calculator

From balance, APR and monthly payment, compute the months, total paid and total interest to clear the debt.

Credit Card Interest Calculator

From balance, APR and monthly payment, compute the total interest paid while clearing the debt.

Balance Transfer Calculator

Compare the total cost of moving a credit-card balance to a low-rate promo card versus keeping it on the old card, to see if a balance transfer is worth it.

Compute the real annual percentage rate (APR) and total repayment cost of a payday loan, revealing the true cost of short-term high-interest borrowing.

Loan Comparison Calculator

Compare up to three loans side by side on monthly payment, total interest and total repayment to pick the cheapest plan.

Balloon Payment Calculator

Work out the monthly instalment and the large final balloon payment for an amortising loan with a balloon term.

Blended (Weighted Average) Interest Rate Calculator

Combine several debts at different balances and rates into a single weighted-average effective rate.

Loan Balance Calculator

From original loan, rate, term and months elapsed, compute the remaining principal balance still owed.

Loan Repayment Calculator

From loan amount, annual rate and term, compute the amortising monthly payment, total repayment and total interest.

Deferred Payment Loan Calculator

From principal, rate, term and a deferral (grace) period, compute the new balance after interest capitalisation and the post-deferral monthly payment.

Compute the monthly PITI total of a mortgage — principal, interest, property tax, and insurance — to assess the true monthly cost of homeownership.

Refinance Break-Even Calculator

Find the break-even point of refinancing a mortgage or loan: refinance cost ÷ monthly saving gives the months to break even.

Loan Interest Calculator

Calculate the total interest, total repayment and monthly instalment of an equal-monthly-instalment loan.

Mortgage Interest Calculator

Compute the total interest, total repayment and monthly payment of a mortgage over its full term to see the true cost of home ownership.

Using simple interest, compute the interest that accrues after a court judgment, from the judgment date to the actual payment date, and the total amount due.

Loan Payment Calculator

Calculate the monthly instalment, total repayment and total interest of a fixed instalment loan using the amortising method.

Home Loan Calculator

From loan amount, annual rate and term, compute a home loan's monthly payment, total repayment and total interest to assess long-term affordability.

Cash-Out Refinance Calculator

From current balance, rates, cash-out and costs, compute the new loan, monthly payment change, refinance cost and net cash received.

HELOC Calculator

Estimate a Home Equity Line of Credit's draw-period interest-only and repayment-period amortised monthly payments and total interest.

Car Loan Refinance Calculator

Compare monthly payment and total interest before and after refinancing a car loan, and see the monthly savings and interest difference.

Home Improvement Loan Calculator

From loan amount, annual rate and term, compute the amortised monthly payment, total repayment and total interest for a renovation loan.

Land Loan Payment Calculator

Estimate the monthly payment, total repayment and total interest of a land/plot purchase loan (amortising).

Compute the monthly payment, total repayment, and total interest of a recreational vehicle (RV / motorhome) loan to gauge the borrowing burden.

Compute the monthly payment, total repayment, and total interest of a student or education loan, to plan your post-graduation repayment burden.

Compare the monthly payment and total interest before and after refinancing (remortgaging), and compute the refinance cost, monthly savings, and break-even months.

Credit Card Payoff Calculator

From balance, APR and monthly payment, compute the months, total paid and total interest to clear the card.

Credit Card Monthly Payment Calculator

Set a target payoff period and work backwards to the required monthly payment, plus total paid and total interest.

Lease Calculator

From asset value, residual value, rate and term, compute monthly lease payment, total payments, interest and cost to own.

Lease Excess Mileage Calculator

Predict lease-end excess mileage, penalty and monthly savings needed from current speed, term and allowance.

Compute the monthly payment, total repayment, and total interest of a student loan, to plan your post-graduation repayment burden.

Loan Calculator

Compute the monthly payment, amount received after origination fee, total repayment, total interest and total finance charge.

Loan Amortization Calculator

Calculate the monthly instalment, total repayment and total interest of an equal-instalment (amortising) loan, with the first-period interest/principal split.

Debt Consolidation Calculator

Compare keeping your current debts against consolidating them into one lower-rate loan: monthly payment, months to clear and total interest difference.

Just enter the loan amount, annual rate, and repayment term to quickly compute the monthly payment, total repayment, and total interest.

Home Mortgage Calculator

Plan a home mortgage: enter the loan amount, annual rate and term to get the monthly instalment, total repayment and total interest.

After Repair Value (ARV) Calculator

Estimate a property's after-repair value (ARV), the 70% rule max offer, potential profit and ROI for flipping.

Average Daily Rate (ADR) Calculator

Compute a hotel or homestay's Average Daily Rate (ADR) and, with occupancy, Revenue per Available Room (RevPAR).

Commercial Lease Calculator

From monthly rent, escalation and fit-out, compute the average monthly cost and total occupancy cost over a commercial lease term.

Gift of Equity Calculator

Compute the gift of equity when a property is sold below market value to a relative: market value − sale price, and its percentage of market value.

Adjustable-Rate Mortgage (ARM) Calculator

Estimate the monthly instalments, outstanding balance and total interest of an adjustable-rate mortgage (ARM) across the initial fixed-rate period and after the rate reset.

Rule of 72 Calculator

Use the Rule of 72 to quickly estimate how many years it takes for a sum to double at a fixed annual return, with an exact calculation for comparison.

Annuity Calculator

Estimate the accumulation of a regular fixed savings plan: final balance (future value), total deposits and total return.

Annuity Payout Calculator

Work out the fixed amount you can draw from a lump sum over a chosen term, plus total payout and total interest.

Savings Withdrawal Calculator

With a fixed monthly withdrawal and an annual return, see how many years and months your savings balance will last.

Retirement Withdrawal Calculator

Work out the fixed monthly amount you can withdraw from a retirement balance so it is exactly exhausted at the end of your retirement (beginning-of-period withdrawals).

Annuity Future Value Calculator

Work out the future value of a regular fixed contribution under compounding, with total contributed and interest earned.

Annuity Present Value Calculator

Calculate the present value (today's worth) of a stream of regular future payouts, with total payouts and the discount gap.

Immediate Annuity Calculator

Estimate the fixed monthly income from a lump-sum premium over a chosen term, and its annual payout rate.

Growing Annuity Calculator

Compute the future value of an annuity whose contributions rise by a fixed rate each year, with cumulative contributions and interest earned.

Early Retirement (FIRE) Calculator

From current savings and monthly contributions, work out the years and months to reach your target retirement fund.

Discount Calculator

Enter the original price and a discount percentage to get the final price and the amount saved.

Double (Stacked) Discount Calculator

From an original price and two sequential discounts, compute the final price, total saved and the equivalent single discount rate.

Markup Calculator

From the cost and a markup percentage, work out the selling price, profit per unit and the corresponding profit margin.

From selling price and cost, compute gross profit, gross margin percentage, and the corresponding markup percentage.

Given cost, target gross margin, and a discount, work backwards to the list price and the discounted selling price.

Cash Back Calculator

From spend and the cash-back rate, compute the cash rebate you earn; compare flat vs tiered rates and annual cap.

Commission Calculator

From sales amount and commission rate (or tiered slabs), compute the commission earned and the effective rate.

Markdown Calculator

From the original price and the current price, work out how much was marked down and the markdown percentage (discount).

Triple Discount Calculator

From the original price and three sequential discounts, compute the price after each step, the final price, the total saved and the single equivalent discount rate.

Customer Lifetime Value (CLTV) Calculator

From average order value, purchase frequency and lifespan, estimate a customer's lifetime value (LTV).

Break-Even Point Calculator

From fixed cost, price and variable cost, compute contribution per unit, contribution margin and the break-even units and revenue.

Contribution Margin Calculator

From revenue and variable costs, compute the contribution margin and the contribution margin ratio.

Cost of Goods Sold (COGS) Calculator

From beginning inventory, purchases and ending inventory, compute COGS and the gross profit and margin.

From the initial investment and annual net cash flow, compute the years and months needed to recover the investment.

Profitability Index Calculator

From the present value of cash flows and the initial investment, compute the profitability index (PI) and the net present value (NPV).

Burn Rate & Cash Runway Calculator

From beginning and ending cash and the elapsed months, compute the monthly net burn and how many months the cash will last (runway).

Customer Acquisition Cost (CAC) Calculator

From total sales & marketing spend and new customers, compute the customer acquisition cost (CAC) and its ratio to revenue.

ROAS Calculator

From ad revenue and ad spend, compute ROAS: revenue ÷ ad spend, how many dollars of revenue each ad dollar brings.

Business Budget Calculator

From total income and total expenses, compute the net surplus and the surplus ratio to check if the business budget balances.

Labor Cost Calculator

From hourly wage, hours per week, weeks per year and headcount, estimate per-employee and total annual labor cost.

Customer Retention Rate (CRR) Calculator

From starting customers, ending customers and new acquisitions, compute the true retention of existing customers (CRR).

Customer Churn Rate Calculator

From starting customers and customers lost in a period, compute the churn rate and the retention rate.

From total revenue and headcount, compute the average revenue each employee generates, measuring team productivity.

Conversion Rate Calculator

From conversions and visitors/impressions, compute the conversion rate (CR) — a core marketing and sales-funnel metric.

Cost Per Acquisition (CPA) Calculator

From total ad spend and actions (conversions), compute the cost per action — a measure of ad cost-efficiency.

Consulting Fees Calculator

From target income, work weeks, billable hours, overhead and profit, derive the hourly rate a self-employed consultant should charge.

Cost of Doing Business Calculator

From fixed cost, variable cost and units produced, compute the total cost and the cost per unit.

CPC & CPM Calculator

From ad spend, clicks and impressions, compute cost per click (CPC) and cost per mille (CPM, per 1,000 impressions).

Business Loan Calculator

On an equal-monthly-instalment basis, compute the monthly payment, total repayment and total interest for a business loan.

Liquid Net Worth Calculator

From quickly-realised liquid assets minus total liabilities, compute your liquid net worth.

Average Fixed Cost (AFC) Calculator

Spread total fixed cost across output to get the average fixed cost per unit (AFC).

Click-Through Rate (CTR) Calculator

From clicks and impressions, compute the click-through rate — how often a viewed ad/link gets clicked.

FTE Calculator

Convert the total hours of full-time and part-time staff into the equivalent number of full-time employees.

Pre & Post-Money Valuation Calculator

From the pre-money valuation and the investment, compute the post-money valuation and the equity stake the investor receives.

From monthly revenue per customer, gross margin, and monthly churn rate, estimate a SaaS customer's lifetime value (LTV).

Accumulated Depreciation Calculator (Straight-Line)

Using the straight-line method, compute annual depreciation, accumulated depreciation to date and current book value.

Employee Attrition Rate Calculator

From beginning and ending headcount and separations, compute the employee attrition rate.

Average Collection Period Calculator

From accounts receivable and net credit sales, work out how many days on average it takes to collect cash from customers.

Effective Corporate Tax Rate Calculator

For a company, compute the effective corporate tax rate from pre-tax profit, tax and tax-deductible expenses.

GMROI Calculator

From revenue, COGS and average inventory cost, compute gross margin return on investment — how much gross profit each dollar of inventory earns.

Accounts Receivable Days (DSO) Calculator

From accounts receivable and annual revenue, work out how many days on average it takes to collect cash from sales.

Bounce Rate Calculator

Work out the bounce rate of a website or page from single-page sessions and total entries.

High-Low Method Calculator

From the highest and lowest activity and total cost, estimate the variable cost per unit, fixed cost and separate them — a quick cost-behaviour tool.

Man-Hours Calculator

Estimate the total man-hours of a job or project from the number of workers, hours per worker per day and the number of days.

From revenue and operating assets, compute how much revenue each dollar of operating assets generates.

Exit Rate Calculator

From a page's exits and page views, compute the share of visits that leave the site from that page.

Marketing Conversion Rate Calculator

From the number of conversions and visits, work out the conversion rate of an online marketing campaign.

From the unit price and quantity, compute the total revenue (or total amount).

Inventory Turnover Calculator

Compute inventory turnover and days sales of inventory from cost of goods sold and average inventory.

Revenue Calculator

From units sold, unit price and a discount rate, compute the total revenue.

CPM (Cost Per Mille) Calculator

From ad cost and impressions, compute the cost per 1,000 impressions (CPM).

From total revenue and total expenses, compute the net income (profit) for a business or individual.

Gross Margin Calculator

From revenue and COGS, compute gross profit and gross margin — the profit left per dollar of revenue after direct costs.

From operating income and revenue, compute the operating margin that reflects core-business profitability efficiency.

From net income and revenue, compute the ratio of how much each dollar of revenue turns into net profit.

EBIT Calculator (Earnings Before Interest and Taxes)

From net income plus interest and tax, compute EBIT — operating profit before financing and tax effects.

EBITDA Calculator (Earnings Before Interest, Tax, Depreciation & Amortization)

From EBIT plus depreciation and amortisation, compute EBITDA — a cash-closer proxy for operating earnings.

Profit Calculator

From revenue and cost, compute the profit (the surplus of revenue over cost).

From current assets and current liabilities, compute the working capital that reflects short-term solvency and operating flexibility.

Receivables Turnover Calculator

From net credit sales and average receivables, compute the receivables turnover ratio and the days sales outstanding.

Current Ratio Calculator

From current assets and current liabilities, compute the current ratio — a measure of short-term solvency.

Cash Ratio Calculator

From cash plus marketable securities and current liabilities, compute the cash ratio — the strictest liquidity measure.

EBT Calculator

Enter revenue, operating costs and non-operating items to compute earnings before tax (EBT) = revenue − operating costs + non-operating income − non-operating expense.

EBITDA Margin Calculator

From EBITDA and revenue, compute the EBITDA margin — core operating cash profitability per revenue dollar.

From revenue and average total assets, compute the total asset turnover ratio that reflects how efficiently assets generate sales.

Financial Leverage Ratio Calculator

From average total assets and average shareholders' equity, compute the equity multiplier that shows financial leverage.

Fixed Asset Turnover Calculator

From revenue and average net fixed assets, compute the fixed asset turnover that reflects how efficiently long-term assets generate sales.

From short-term debt, long-term debt, and cash and cash equivalents, compute the net debt that reflects the true debt burden.

Cash Flow to Debt Ratio Calculator

From operating cash flow and total debt, compute the cash-flow-to-debt ratio — a debt-repayment capacity measure.

Accounting Profit Calculator

From total revenue and explicit costs, work out the accounting profit shown on the income statement.

From the change in total cost and output, compute the marginal cost of producing one more unit.

Marginal Revenue Calculator

From the change in total revenue and the change in quantity sold, work out the marginal revenue of each extra unit sold.

Retained Earnings Calculator

From the beginning retained earnings, net income and dividends, compute the ending retained earnings.

From the previous and current revenue, compute the revenue growth rate that reflects the pace of business expansion.

Using the indirect method, compute operating cash flow from net income, non-cash expenses, and the change in working capital.

Days Sales Outstanding (DSO) Calculator

From accounts receivable and credit sales, compute how many days it takes to collect payment (DSO).

Days Inventory Outstanding (DIO) Calculator

From average inventory and cost of goods sold, compute how many days inventory sits before being sold (DIO).

Days Payable Outstanding (DPO) Calculator

From accounts payable and cost of goods sold, compute how many days a company takes to pay suppliers (DPO).

Cash Conversion Cycle (CCC) Calculator

From DIO, DSO and DPO, compute the cash conversion cycle: how many days cash is tied up from buying to collecting.

Economic Profit Calculator

Enter NOPAT, invested capital and the cost of capital to compute economic profit = NOPAT − (capital × cost of capital), judging whether a business truly creates shareholder value.

Free Cash Flow Calculator

From operating cash flow minus capital expenditure, compute the free cash flow a company can use freely.

From revenue and average working capital, compute the turnover ratio: how much revenue each dollar of working capital generates.

Subtract operating current liabilities from operating current assets to compute the net operating working capital (NOWC) needed for day-to-day operations.

Productivity Calculator

Divide output by input to get the output produced per unit of input (productivity).

Subtract operating liabilities from operating assets to compute the net operating assets (NOA) a business has invested in its operations.

FCFF Calculator

From operating cash flow, after-tax interest and capital expenditure, compute the free cash flow to firm (FCFF) for all capital providers.

Free Cash Flow to Equity Calculator

From net income, add back non-cash items and subtract capital expenditure, changes in net working capital and net debt repayment, to get the cash truly available to shareholders.

Depreciation Calculator

From asset cost, salvage value and useful life, compute the straight-line annual depreciation and yearly schedule.

Ending Inventory Calculator

From opening inventory, purchases and COGS, compute the closing inventory using the basic inventory formula.

From the previous month's and current month's values, compute the month-over-month (MoM) percentage change.

From EBIT, tax rate, depreciation and amortization, capital expenditure, and change in working capital, compute the unlevered free cash flow independent of financing structure.

Levered Free Cash Flow (LFCF) Calculator

From UFCF, after-tax interest and net borrowing, compute the cash flow truly available to equity holders.

Goodwill Calculator

From purchase price, fair value of identifiable assets and liabilities assumed, compute the goodwill arising from a business combination.

FFO Calculator

From net income, depreciation & amortisation, and gains/losses on asset sales, compute Funds From Operations (FFO) for REITs and similar firms.

Actual Cash Value (ACV) Calculator

From replacement cost, age and useful life, compute the depreciated actual cash value (ACV) of an asset.

Accrual Ratio Calculator

From net income, operating and investing cash flows and average total assets, compute the accrual ratio as an earnings-quality gauge.

Average Variable Cost (AVC) Calculator

From total variable cost and output, compute the average variable cost per unit (AVC).

Consumer Surplus Calculator

From the maximum willingness-to-pay, market price and quantity, estimate consumer surplus under a linear-demand approximation.

Degree of Operating Leverage (DOL) Calculator

From contribution margin and operating income, compute the DOL — how much a sales change amplifies the change in operating profit.

EOQ Calculator

From annual demand, ordering cost and holding cost, compute the economic order quantity that minimises total inventory cost.

Price Elasticity of Demand Calculator

Using the midpoint method on price and quantity changes, compute the price elasticity of demand, how sensitive demand is to price.

Cross-Price Elasticity Calculator

Using the midpoint method, compute how the demand for X responds to a price change of Y — substitutes or complements.

Income Elasticity of Demand Calculator

Use the midpoint method to measure how sensitive demand is to income changes, classifying a good as normal, luxury or inferior.

Optimal Price Calculator

From the unit cost and the price elasticity of demand, find the profit-maximising price using the monopoly pricing formula.

From the unit price, quantity sold, and discount, compute the net sales revenue after discounts.

Dividend Yield Calculator

Work out a stock's dividend yield from the annual dividend per share and the share price.

Dividend Payout Ratio Calculator

From total dividends and net income, compute the payout ratio — the share of profit paid out as dividends.

EPS Calculator

From net income, preferred dividends and weighted average shares, compute earnings per share (EPS).

From the share price and earnings per share, compute the price-to-earnings (P/E) ratio to gauge stock valuation.

Market Capitalization Calculator

From the share price and shares outstanding, compute a company's market capitalization.

Return on Equity Calculator

From net income and shareholders' equity, compute ROE: net income ÷ shareholders' equity × 100, the return to shareholders.

Return on Assets Calculator

From net income and total assets, compute ROA: net income ÷ total assets × 100, how profitably a company uses its assets.

From the share price and book value per share, compute the price-to-book (P/B) ratio to gauge whether a stock trades above or below its book value.

Retention Ratio Calculator

From net profit and total dividends, compute the retention ratio, the share of earnings kept for reinvestment.

Price-to-Sales Ratio Calculator

From market cap and total revenue, compute the price-to-sales ratio (P/S) to value a stock by its revenue.

Enterprise Value Calculator

From market capitalisation, total debt and cash, compute the enterprise value (EV).

PEG Ratio Calculator

From the P/E ratio and the EPS growth rate, compute the PEG ratio to judge whether a valuation is justified by growth.

EV/Sales Multiple Calculator

From enterprise value and total revenue, compute the EV/Sales (EV to Sales) multiple.

From the share price and operating cash flow per share, compute the price-to-cash-flow (P/CF) ratio.

Sustainable Growth Rate Calculator

From ROE and the retention ratio, compute the sustainable growth rate a company can sustain without issuing new equity.

ROIC Calculator

From NOPAT and invested capital, compute ROIC: NOPAT ÷ invested capital × 100, the return on all capital (debt + equity) the business uses.

From operating profit and operating revenue, compute the return on sales (ROS), i.e. the operating profit margin.

DuPont Analysis Calculator

From net margin, asset turnover and equity multiplier, decompose and compute the Return on Equity (ROE).

EPS Growth Rate Calculator

From beginning and ending EPS, compute the growth rate of earnings per share.

Residual Income Calculator

From net profit, equity and the required return, compute the residual income after the cost of equity capital.

Cost of Equity Calculator

Using CAPM, compute the cost of equity (the return shareholders require) from the risk-free rate, beta and market return.

Capital Asset Pricing Model (CAPM) Calculator

Estimate the expected return (cost of equity) using the risk-free rate, beta and market risk premium.

WACC Calculator

From the market values of equity and debt, their costs and the tax rate, compute the weighted average cost of capital (WACC).

Graham Number Calculator

From EPS and book value per share, estimate the price ceiling for a defensive investor via the Graham number: √(22.5 × EPS × BVPS).

Calculate the margin of safety percentage for an investment based on its intrinsic value and market price.

Intrinsic Value Calculator

Estimate a stock's intrinsic value by discounting a stable dividend at the required return minus growth.

From total assets, total liabilities, and shares outstanding, compute the net asset value (NAV) per share.

EBITDA Multiple Calculator (EV/EBITDA)

From enterprise value and EBITDA, compute the EV/EBITDA multiple — a relative valuation benchmark.

Economic Value Added (EVA) Calculator

Enter NOPAT, invested capital and WACC to compute EVA = NOPAT − (capital × WACC), the surplus return above the cost of capital.

From operating cash flow and current liabilities, compute the operating cash flow ratio, measuring short-term solvency.

Dividend Calculator

From dividend per share, share price and shares held, compute the dividend yield and the annual dividend income.

Stock Average Cost Calculator

From two buy lots (shares and price each), compute the weighted average buy price, total shares and total cost — useful for averaging down.

Stock Split Calculator

From the original shares, original price and the split ratio, compute the shares and price per share after a split or reverse split.

From levered beta, the tax rate, and the debt-to-equity ratio, strip out the effect of debt to recover the unlevered (asset) beta.

Free Float Calculator

From shares outstanding and restricted shares, compute the freely tradable free-float shares and the free-float ratio.

Stock Beta Calculator

Compute a stock's beta from its correlation with the market and the two return volatilities.

Cost of Capital (WACC) Calculator

From the weights, cost of equity, cost of debt and tax rate, compute the weighted average cost of capital (WACC).

Dividend Discount Model (DDM) Calculator

Using the Gordon Growth Model, estimate a stock's intrinsic value from next dividend, required return and dividend growth.

From the weights and betas of three assets, compute the portfolio's weighted-average beta (βp).

Stock Profit & Loss Calculator

From the buy price, sell price and number of shares, compute the profit or loss amount and the return rate of a share trade.

Carried Interest Calculator

From total fund profit and the carry rate, compute the general partner's (GP) performance fee (carried interest).

Maturity Value Calculator

From the principal, annual rate, compounding frequency and term, compute the value of a deposit or investment at maturity.

Absence Rate Calculator

From absent days and scheduled work days, work out the absence rate as a percentage for an employee or a team.

Employee Turnover Rate Calculator

From the number of separations and the average headcount, compute the employee turnover rate as a percentage.

Sell-Through Rate Calculator

From units sold and units received, compute the sell-through rate: units sold ÷ units received × 100, the share of stock sold in a period.

Additional Funds Needed (AFN) Calculator

From assets, sales, spontaneous liabilities and retained earnings, estimate the external funding a company must raise to support growing sales.

HHI Calculator

From the market shares of competitors, compute the Herfindahl-Hirschman Index (HHI) — a measure of market concentration.

Lerner Index Calculator

From price and marginal cost, compute the Lerner Index of a firm's market/price-setting power.

From the deal amount and commission rate, compute the commission a salesperson or agent earns.

Safety Stock Calculator

From the maximum and average daily usage and lead times, compute the safety stock needed to cover demand swings and delays.

Bradford Factor Calculator

From absence spells and total absence days, compute the Bradford Factor score that measures an employee's absence pattern.

EMV Calculator

From the probability of a risk and its financial impact, compute the expected monetary value of a project risk or decision.

Gross Rating Points Calculator

From reach and frequency, compute gross rating points (GRP) — the total ad exposure of a campaign.

Parking Ratio Calculator

From the number of parking spaces and the building area, compute the parking spaces per 1,000 square feet of a commercial property.

From the share price, EPS, and required return, compute the premium the market pays for the company's future growth (PVGO).

Build vs Buy Calculator

Compare the total cost of ownership of building in-house vs buying/subscribing over a chosen period, to decide which is cheaper.

Business Valuation Calculator

Using the earnings-multiple method, estimate a business value from its annual earnings and a valuation multiple.

FIFO Inventory Calculator

Compute the cost of goods sold (COGS) under the first-in, first-out (FIFO) method from old and new cost layers and the units sold.

Convert years and months of service into a single total years of tenure.

Website Ad Revenue Calculator

From monthly page views and the revenue per mille (CPM), estimate a website's advertising revenue.

Burndown Chart Calculator

From total work, total days and elapsed days, compute the ideal burndown rate and ideal remaining work for an Agile project.

Earned Value Management Calculator

Enter planned value (PV), earned value (EV) and actual cost (AC) to compute cost/schedule variance and CPI/SPI, judging whether the project is over/under budget and ahead/behind.

Google AdSense Revenue Calculator

From pageviews, click-through rate (CTR) and cost per click (CPC), estimate AdSense advertising revenue.

Software Contract Value Calculator

From monthly recurring revenue, contract years and one-time fees, compute the total contract value (TCV) of a software subscription.

YouTube Money Calculator

From video views and the revenue per mille (RPM), estimate a creator's YouTube ad earnings.

Direct Material Price Variance Calculator

From standard price, actual price and actual quantity, compute the material price variance (favourable or unfavourable).

Lemonade Stand Calculator

From cups sold, price, variable cost per cup and fixed cost, compute revenue, total cost and profit.

From the transaction amount, percentage fee rate, and fixed fee, compute the PayPal fee and the net amount you actually receive.

Percentage Discount Calculator

From the original price and a discount percentage, compute the discounted price and the amount saved.

Percent Off Calculator

From the original price and a percent-off (X% off), compute the sale price and the amount saved.

Black Friday Discount Calculator

During Black Friday sales, quickly compute the discounted price and amount saved from the original price and discount percentage.

Cyber Monday Discount Calculator

During the Cyber Monday online sale, compute the discounted price and amount saved from the original price and discount percentage.

Given cost, target gross margin, and sales tax rate, compute the pre-tax price, tax amount, tax-inclusive price, and profit.

Margin & VAT Calculator

From cost, target margin and VAT rate, work out the price excluding VAT, the VAT amount, the price including VAT and the profit.

Margin & Markup Calculator

From the cost and a target profit margin, work out the selling price, the profit and the corresponding markup percentage.

Debt-to-Asset Ratio Calculator

From total liabilities and total assets, compute the debt-to-asset ratio — how much of assets is financed by debt.

Debt-to-Equity Ratio Calculator

From total liabilities and shareholders' equity, compute the D/E ratio — a core measure of financial leverage.

Debt-to-Capital Ratio Calculator

From total debt and equity, compute the debt-to-capital ratio — the share of total capital funded by debt.

From current assets, inventory, and current liabilities, compute the quick ratio, measuring short-term liquidity without relying on inventory.

Interest Coverage Ratio Calculator

From EBIT and interest expense, compute the interest coverage ratio to gauge a company's ability to pay interest.

Bond Current Yield Calculator

Compute a bond's current yield from its face value, coupon rate and current market price.

Bond Coupon Rate Calculator

Derive a bond's annual coupon rate from its face value and annual coupon payment.

Bond Coupon Payment Calculator

Work out the coupon paid per period and the total annual coupon from a bond's face value, coupon rate and frequency.

From EBIT and interest expense, compute the times interest earned (TIE) ratio, measuring a company's ability to cover its interest payments.

After-Tax Cost of Debt Calculator

From pre-tax cost of debt and tax rate, compute the after-tax cost of debt (after-tax cost of debt), the real borrowing cost after the interest tax shield.

Bond Price Calculator

Estimate a bond's theoretical clean price by discounting its coupon payments and face value at a given yield.

Bond Equivalent Yield (BEY) Calculator

From face value, purchase price and days to maturity, compute the bond equivalent yield (annualised, 365-day basis).

Credit Spread Calculator

From a bond yield and the risk-free rate, compute the credit spread (yield spread) that compensates for default risk.

Debt Service Coverage Ratio (DSCR) Calculator

From net operating income and total debt service, compute the DSCR — the ability to cover debt payments from operating income.

Defensive Interval Ratio (DIR) Calculator

From liquid assets and annual operating expenses, compute the defensive interval (in days) — how long a firm survives with no new revenue.

Effective Duration Calculator

From a bond's initial price and its repriced values when yield rises and falls, compute the effective duration — the bond's interest-rate sensitivity.

Bond Convexity Calculator

From the price at an initial yield and at yields up/down, estimate the bond's convexity — the curvature of the price-yield curve.

Taxable Equivalent Yield Calculator

From a tax-free investment's yield and your applicable tax rate, compute the taxable equivalent yield (TEY) to compare tax-free bonds with taxable investments fairly.

Altman Z-Score Calculator

Estimate a company's bankruptcy-risk Z-score from five financial ratios (manufacturing model).

Loss Given Default (LGD) Calculator

From exposure at default and recovery value, compute the loss given default rate of a loan/credit asset.

GDP Calculator

Compute GDP by the expenditure approach: C + I + G + (X − M), the total market value of final goods and services produced in a period.

GDP per Capita Calculator

From GDP and population, compute GDP per capita = GDP ÷ population, the average output per person, used to compare living standards across regions.

GDP Growth Rate Calculator

From current and previous GDP, compute the growth rate: (current − previous) ÷ previous × 100%, measuring expansion or contraction between two periods.

CPI Inflation Rate Calculator

From the current and previous Consumer Price Index, compute the inflation rate: (CPI_now - CPI_prev) / CPI_prev x 100%.

From the number of unemployed and the labour force, compute the unemployment rate: unemployed ÷ labour force × 100, the share of the workforce who want a job but cannot find one.

Real GDP Calculator

From nominal GDP and the GDP deflator, compute real GDP: nominal GDP ÷ (GDP deflator ÷ 100), the true output after stripping out price changes.

GDP Deflator Calculator

From nominal GDP and real GDP, compute the GDP deflator: nominal GDP ÷ real GDP × 100, measuring overall price change vs the base period.

Real Interest Rate Calculator

From the nominal rate and inflation, compute the real interest rate (Fisher equation): (1 + nominal) ÷ (1 + inflation) − 1, the true return after prices rise.

From the reserve requirement ratio, compute the money multiplier: 1 ÷ reserve ratio, showing how much the banking system expands base money under fractional reserves.

Velocity of Money Calculator

From nominal GDP and the money supply, compute the velocity of money: nominal GDP ÷ money supply, the average times a dollar is spent per period.

Marginal Propensity to Consume Calculator

From the change in consumption and the change in disposable income, compute the marginal propensity to consume: how much of each extra dollar is spent.

Marginal Propensity to Save Calculator

From the change in saving and the change in disposable income, compute the marginal propensity to save: how much of each extra dollar is saved.

Spending Multiplier Calculator

From the marginal propensity to consume (MPC), compute the spending multiplier: 1 ÷ (1 − MPC), how much total output one yen of spending ultimately drives.

Reserve Ratio Calculator

From reserves and total deposits, compute the reserve ratio: reserves ÷ total deposits × 100, the share of deposits a bank must hold as reserves.

From currency in circulation and demand deposits, compute the money supply: cash plus demand deposits, measuring the immediately spendable money stock (M1).

Labor Force Participation Rate Calculator

From the labor force and working-age population, compute the participation rate: labor force ÷ working-age × 100.

From the frictional and structural unemployment rates, compute the natural rate of unemployment: frictional rate plus structural rate, the 'normal' unemployment level when the economy is at full employment.

Output Gap Calculator

From actual and potential GDP, compute the output gap: (actual − potential) ÷ potential × 100%, measuring how far output is above or below capacity.

Disposable Income Calculator

From gross income and direct taxes, compute disposable income: income after tax, free for consumption and saving.

Discretionary Income Calculator

From disposable income and necessary expenses, compute discretionary income: what is left to spend freely after essentials.

Buying Power Calculator

From cash, margin multiplier and unrealised P/L, compute your available buying power for trading.

Fisher Effect Calculator

From nominal and real rates, or inflation, compute the Fisher effect — how inflation and nominal rates relate to the real rate.

From the unemployment-rate gap and Okun coefficient, estimate the output gap: output gap = −Okun coefficient × (actual unemployment − natural unemployment), quantifying the link between joblessness and economic output.

Private Savings Calculator

From national income, net taxes and consumption, compute private savings: private savings = national income − net taxes − consumption (Y − T − C).

Estimate the central bank policy rate using the Taylor rule: i = r* + π + 0.5(π − π*) + 0.5(output gap), as a benchmark for monetary policy.

Phillips Curve Calculator

Estimate inflation from the Phillips curve: inflation = expected inflation − coefficient × (actual unemployment − natural unemployment), showing the short-run trade-off.

Fisher Equation Calculator

From nominal rate and inflation, compute the real rate: real = (1 + nominal) ÷ (1 + inflation) − 1, to see true post-inflation return.

Gini Coefficient Calculator

From individual incomes, compute the Gini coefficient — a 0-to-1 measure of income inequality; 0 is perfect equality, 1 is full concentration.

Purchasing Power Parity Calculator

From the price of a basket in two places, compute the PPP implied exchange rate to judge if a currency is over- or under-valued.

Price Elasticity of Supply Calculator

From changes in price and quantity supplied, compute the price elasticity of supply (PES), how sensitive supply is to price.

Cobb-Douglas Production Function Calculator

From total factor productivity, capital, labour and elasticities, compute output and the returns-to-scale property.

Comparative Advantage Calculator

From the output of two goods, compute the opportunity cost of producing good 1 — and thus who has the comparative advantage.

Currency Forward Rate Calculator

From the spot rate and two interest rates, compute the forward rate (covered interest parity, with days): F = S x (1 + r_f·T) / (1 + r_d·T), T = days/360.

Deadweight Loss Calculator

From the quantity change and price wedge caused by a tax or control, compute the deadweight loss: DWL = 0.5 x quantity change x price change (welfare triangle).

Interest Rate Parity Calculator

Compute the theoretical forward rate from spot and two rates under covered interest parity; judge arbitrage.

Carry Trade Calculator

From principal, rates and FX change, compute the net return of a carry trade: borrow low, invest high, minus currency movement.

Liquidity Coverage Ratio (LCR) Calculator

From high-quality liquid assets and 30-day net cash outflows, compute a bank's liquidity coverage ratio.

Net Stable Funding Ratio Calculator

Compute a bank's Net Stable Funding Ratio (NSFR): NSFR = available stable funding (ASF) ÷ required stable funding (RSF) × 100%, a measure of medium-term funding stability.

Forward Premium / Discount Calculator

Compute the annualised forward premium or discount of a currency: (forward − spot) ÷ spot × (360 ÷ days) × 100%, to see if it trades rich or cheap to spot.

Using put-call parity, derive the theoretical European call price: C = P + S − K ÷ (1 + r)^t, linking call, put, underlying, and strike.

Deferred Annuity Calculator

From a deferral period, annual payment, rate and years of payment, compute the present value of a deferred annuity.

Variable Annuity Calculator

Estimate a variable annuity's accumulation value: FV = principal × (1 + r)^n, compounded at an assumed annual return until the payout phase.

Compute a year's rest days and actual working days: days off = weekly rest days × weeks per year + public holidays; working days = total days − days off.

Debt Payoff Calculator (Months)

Solve the months to clear a debt at a fixed monthly payment: n = -ln(1 - r·balance / payment) / ln(1 + r), with r = monthly rate.

Zakat Calculator

Compute the Zakat due: Zakat = net zakatable wealth × Zakat rate (usually 2.5%), to estimate the Islamic wealth-purification donation.

Annual Income Calculator

Convert an hourly wage into gross annual and monthly income using your working-hour assumptions.

Estimate the annual productivity cost to an employer from smoking breaks: annual cost = smoking breaks per day × minutes per break × (hourly wage ÷ 60) × working days per year.

Calculate the monthly payment and balloon payment of a partially amortized loan: the payment uses a longer full amortization term, leaving an unpaid balance (balloon) at the shorter maturity.

LIFO Inventory Calculator

Under LIFO, compute COGS and ending inventory: sold units take the most recent batch cost first; remaining use earlier batches.

AFFO / FFO Calculator (REIT Funds from Operations)

Compute a REIT's Funds From Operations (FFO) and Adjusted FFO (AFFO): FFO = net income + depreciation & amortisation - gain on property sales; AFFO = FFO - recurring capex - straight-line rent adjustment.

Compute the new salary and raise amount after a raise: raise amount = old salary × raise percentage; new salary = old salary + raise amount.

Overtime Pay Calculator

Compute total pay with overtime: regular pay = wage × regular hours; overtime pay = wage × multiplier × overtime hours; total is the sum.

Compute a portion of annual salary by the actual working days: prorated salary = annual salary × actual work days ÷ full-year work days.

Mileage Reimbursement Calculator

From the business miles driven, a per-mile rate and other expenses, work out the total mileage reimbursement claim.

Billable Hours Calculator

Split total work hours into billable and non-billable: total = hours/day x days; billable = total x billable %; the rest is non-billable.

Future Salary Calculator

Estimate your salary after years of fixed-rate raises, using compound growth: future salary = current salary × (1 + annual raise rate)^years.

Salary Inflation Calculator

See the real value of your salary after inflation erodes it: real value = salary ÷ (1 + inflation rate)^years; purchasing-power loss = salary − real value.

Bill Rate Calculator

Work out a sustainable hourly bill rate for freelancers: rate = (target income + overhead) x (1 + profit %) / billable hours per year.

Gratuity Calculator

Estimate end-of-service gratuity from last salary and years of service under the minimum severance/gratuity rules.

Salary to Hourly Calculator

Convert an annual salary to an hourly and daily wage: total hours = hours per week × weeks per year; hourly = salary ÷ total hours; daily = hourly × hours per day.

Hourly to Salary Calculator

Convert an hourly wage into annual and monthly salary: annual = hourly × hours/week × weeks/year; monthly = annual ÷ 12.

Salary Conversion Calculator

Convert an annual salary to other periods: monthly = salary ÷ 12; weekly = salary ÷ weeks per year; hourly = weekly ÷ hours per week.

Compute overtime pay: overtime hourly rate = regular hourly wage × overtime multiplier; overtime pay = overtime rate × overtime hours.

Mortgage Prepayment Calculator

See the interest saved and the shorter term from paying extra principal each month, simulated month by month with standard amortisation.

Debt Payoff Calculator

Compare two monthly payment plans side by side — see the months, total paid and total interest saved by paying more.

From MRR, monthly churn, CAC, and ARPU, compute annual recurring revenue (ARR), customer lifetime value (LTV), and the LTV/CAC ratio.

Combined Ratio Calculator

From incurred losses, expenses and earned premiums, compute the combined ratio — the core underwriting profitability gauge for insurers.

Loss Ratio Calculator

From claims paid and earned premium, compute the insurance loss ratio (claims ÷ premium).

Customer Effort Score (CES) Calculator

From the sum of response scores and the number of responses, compute the average Customer Effort Score (CES).

Net Promoter Score Calculator

Compute the Net Promoter Score (NPS): promoters% minus detractors%, a measure of customer loyalty and recommendation.

Using the previous period's high, low, and close, compute the classic pivot point (P) and the first and second resistance (R1, R2) and support (S1, S2) levels as reference prices for intraday trading.

Fibonacci Retracement Calculator

From a swing high and low, compute the 23.6%, 38.2%, 50% and 61.8% retracement levels as potential support/resistance references.

DART Rate Calculator

Compute the DART rate (Days Away, Restricted, or Transferred): DART = qualifying injury cases x 200,000 / total hours — the frequency of severe injuries.

TRIR Calculator

Compute the Total Recordable Incident Rate: TRIR = recordable cases × 200,000 ÷ total hours worked, the standard workplace-injury frequency.

HR Software ROI Calculator

Estimate the ROI of adopting HR software: net benefit = annual benefit − annual cost; ROI = net benefit ÷ annual cost × 100%.

Enter the count of each banknote and coin denomination to automatically total the notes, coins, and cash grand total for counting and reconciliation.

From the average gain and average loss over a period, compute the Relative Strength Index (RSI): RS = avg gain ÷ avg loss; RSI = 100 − 100 ÷ (1 + RS), to judge overbought or oversold market conditions.

Compare the annual total cost of on-site vs remote work models, showing the yearly savings from choosing remote and the savings per worker.

Calculate how many months earlier you can pay off your mortgage and how much interest you save by paying extra principal each month; compare the original and accelerated plans.

Cross Exchange Rate Calculator

From two currencies' rates against a common quote currency, derive the cross rate between them — in both directions.

Currency Converter Calculator

Convert an amount from one currency to another at a given rate, with the reverse conversion for quick comparison.

Mortgage Penalty Calculator

Estimate the penalty and cash-rebate clawback for early mortgage redemption (paying off or refinancing early), the total cost of prepayment.

Mortgage Monthly Payment Calculator

From the mortgage principal, annual rate and term, compute the monthly payment, total repayment and total interest to compare rate scenarios.

True Cost of Real Estate Commission

Beyond the commission itself, add the opportunity cost: what that commission could have earned if invested for several years at a given return.

Forward Rate Calculator

From two spot rates of different maturities, derive the implied forward rate between those dates — the market's implied expectation of future rates.

Futures Contract P&L Calculator

From entry price, exit price, contract multiplier and number of contracts, compute long and short futures profit/loss to quickly assess a trade's outcome.

Margin Call Price Calculator

From the purchase price, initial margin ratio and maintenance margin ratio, find the price at which a leveraged purchase triggers a margin call.

Options Spread Calculator

For a bull call spread, from the two call strike prices and premiums compute the net premium, max profit, max loss and break-even.

Call / Put Option Payoff Calculator

From spot, strike, premium, contracts and contract size, compute the intrinsic value, per-share and total profit, and break-even at expiry (buy-side).

Gross to Net Calculator

From a gross amount and a deduction rate, compute the net amount received and the deducted amount — for salary, income or any proportional reduction.

From a net amount (what you actually want to receive) and a deduction rate, reverse out the gross amount before deductions and the deducted amount, for 'how much to charge to net X' calculations.

Lottery Tax Calculator

From winnings and the applicable tax rate, compute the tax due and the after-tax amount received.

Systematic Withdrawal Plan Calculator

Model a lump sum that earns a return while you withdraw a fixed amount each month; see the ending balance and total withdrawn after a number of years, for retirement or passive cash flow.

EMI Calculator

From loan principal, annual rate and term, compute the fixed monthly instalment (EMI), total repayment and total interest — for personal loans, car loans and instalment plans.

Lumpsum Investment Calculator

Calculate the future value and total gain of a one-off principal invested at a fixed annual return and compounded over a number of years.

Recurring Deposit Calculator

With a fixed monthly deposit into a recurring deposit, compounded monthly, see the maturity value, total deposited and interest earned — good for disciplined saving.

Lumpsum + SIP Calculator

Combine a one-off lump-sum and a monthly SIP at a fixed return to show the merged future value and each part's contribution.

Car Loan EMI Calculator

From car price, down payment, rate and term, compute the loan amount, fixed monthly payment (EMI), total repayment and total interest.

Home Loan EMI Calculator

From loan amount, annual rate and term, compute the fixed monthly EMI, total payment and total interest of a home loan — to assess long-term affordability before buying.

Motorcycle Loan (EMI) Calculator

From the bike price, down payment, rate and term, compute the loan amount, monthly payment and total interest.

Personal Loan EMI Calculator

From the loan amount, annual rate and term, compute the fixed monthly instalment (EMI), total repayment and total interest for a personal loan (P-loan).

Calculate the interest accrued during a loan repayment moratorium, the revised principal afterward, and the recalculated monthly payment for the remaining term, revealing the true cost of deferring payments.

Compute the maturity value, total invested principal, and investment gains of a monthly SIP at a fixed annual return with monthly compounding — ideal for building wealth through regular monthly investing.

Compute the fixed monthly interest from a lump-sum deposit in a fixed-rate Monthly Income Scheme, the total interest over the term, and the principal returned at maturity, suited to those seeking steady monthly cash flow.

Biweekly Mortgage Calculator

Compare standard monthly mortgage payments with a biweekly schedule and see the interest saved and time shortened.

Home Affordability Calculator

Using the 28/36 rule with your annual income and existing debts, estimate the affordable monthly payment, maximum loan and maximum home price.

Interest-Only Mortgage Calculator

Compute the interest-only monthly payment, total interest during the IO period, and the payment jump after it ends.

Enter the loan principal, annual rate, and term to compute the monthly payment, total interest, and total amount paid, revealing the full amortization picture.

Compare two mortgage plans side by side for monthly payment and total interest, showing at a glance which is cheaper and the difference between them.

Calculate how many years earlier you can clear your mortgage and how much interest you save by paying extra each month, showing the long-term benefit of larger payments.

Mortgage Payoff Calculator

See how much interest you save and how much sooner you clear the mortgage by paying extra principal each month on top of the normal instalment.

Mortgage Points Calculator

Work out the cost of buying discount points, the lower payment after the rate drop, and the break-even time to judge if points are worth it.

Mortgage Refinance Calculator

Compare your current mortgage with the refinanced one: monthly saving, break-even time and lifetime interest saved, to judge if refinancing pays off.

Spread free months and one-time concessions across the whole lease to compute the true average monthly rent (net effective rent), for a fair comparison of different listings.

Compute a property's annual net operating income (NOI) after vacancy and operating expenses, a core metric for rental profitability and capitalization rate.

Enter a property's total price and area to get both the price per square meter and per square foot, for easy comparison across listings and units.

When a tenant moves in or out mid-month, compute the partial rent owed based on the actual days occupied.

Rental Property Calculator

Compute a rental property's net operating income (NOI), monthly/annual cash flow, cash-on-cash return and cap rate to assess the investment.

Bond Current Yield Calculator

Compute a bond's current yield — the annual coupon divided by the current market price.

Yield to Maturity Calculator

Estimate a bond's yield to maturity (YTM) with the approximation formula, blending the coupon and the capital gain or loss to maturity into an annualised return.

Yield to Call (YTC) Calculator

Estimate the yield to call of a callable bond: assuming redemption at the earliest call date at the call price, it annualizes the coupons and capital gain or loss.

Black-Scholes Option Pricing Calculator

From spot, strike, time, rate and volatility, compute the theoretical European call and put prices (no dividend).

Annual Percentage Rate (APR) Calculator

Fold upfront fees into a loan to compute the true annual percentage rate (APR), a fairer measure of borrowing cost than the nominal rate.

401(k) Calculator

Enter the starting balance, monthly contribution, annual return and years to retirement to estimate the compounded value, total contributed and gains of a 401(k) account.

IRA Calculator

Estimate the compounded balance, total principal and gains of an IRA/TVC at retirement from balance, monthly contribution, return and years.

Roth IRA Calculator

Enter the initial balance, monthly after-tax contribution, expected annual return, and contribution years to estimate the Roth IRA's compound value at retirement and the tax-free investment gains.

403(b) Calculator

Enter the initial balance, monthly contribution, expected annual return, and contribution years to estimate the compound future value, total principal, and investment gains of a 403(b) retirement account at retirement.

RMD Calculator

Enter the year-end retirement account balance and the life-expectancy factor for the age to compute the required minimum distribution (RMD), the average monthly withdrawal and the withdrawal as a percent of the balance.

PMI Calculator

Enter home price, loan amount, PMI annual rate, mortgage rate, and term to compute the loan-to-value (LTV), monthly principal and interest, monthly mortgage insurance, and first-month total payment.

Jumbo Loan Calculator

Compare monthly payments and lifetime extra interest between a standard and a jumbo (luxury) mortgage rate.

Mortgage Total Cost Calculator

Enter the loan, rate and term plus monthly rates, management fee and insurance to see the principal-and-interest payment, other costs and total monthly outlay.

Tax Bracket Calculator

Enter your net chargeable income to compute the Hong Kong salaries tax under the progressive rates, the effective rate and the marginal rate, and see the tax in each band.

12-Hour Shift Calculator

Enter the hourly rate, shifts per month, and the normal/overtime hours and multiplier per shift to compute per-shift pay, monthly pay, and monthly total hours.

Sales Tax Calculator

Enter a pre-tax amount and sales tax rate to get the tax due and the tax-inclusive total; or reverse out the embedded tax from a tax-inclusive amount.

VAT Calculator

Enter an amount and the VAT rate to reverse out the embedded VAT from a gross price, or add VAT onto a net amount. Useful for mainland China, EU and UK shopping and cross-border claims.

GST Calculator

Add GST to a pre-tax amount or extract the embedded GST from a gross total — for price comparison in Australia, Singapore, Canada and more.

Standard Rate Tax (Alternative Minimum Tax) Calculator

Estimate the Hong Kong standard-rate alternative minimum tax on net chargeable income, plus effective and marginal rates.

AGI Calculator

Enter gross income and deductible items (MPF, charitable donations, self-education, etc.) to compute Adjusted Gross Income (AGI) and the deduction ratio, mapped to Hong Kong's assessable income concept.

MPF Contribution Calculator

Enter monthly salary to compute mandatory MPF contributions: employee and employer each 5%, with a minimum relevant income of HK$7,100 and a cap at HK$30,000 — compared with the US FICA payroll-tax mechanism.

Child Allowance Tax Saving Calculator

From the number of children and marginal tax rate, estimate the Hong Kong child allowance tax saving (HK$130,000 per child).

Modified Adjusted Gross Income Calculator

Enter gross income, deductions and add-backs to compute AGI and MAGI. MAGI adds back tax-exempt interest and foreign income to AGI for assessing benefit or tax-relief eligibility.

GST/QST Dual-Layer Sales Tax Calculator

From a pre-tax amount and the federal GST and provincial QST/PST rates, compute the two tax layers and the included total — for shopping, online buys or quotes in Canada.

Education Savings Calculator

Enter the future education cost, years to go, expected annual return and current savings to compute the monthly saving needed to fund tuition.

High-LTV Mortgage Calculator

From home price, down-payment ratio and annual rate, compute a high-LTV (low down-payment) mortgage's monthly principal & interest, mortgage insurance premium (upfront + monthly) and total payment; compared with the US FHA scheme.

Property Valuation Calculator

Enter the monthly rent, capitalisation rate (cap rate) and expense ratio to estimate a rental property's value by the income approach. Good for judging a fair buy price.

Subsidised Housing Mortgage Calculator

Enter the home price, loan-to-value ratio, and annual rate to compute the high-LTV mortgage monthly payment and total interest for HOS, Green Form, or White Form subsidised housing.

Estate Agent Commission Calculator

From the sale price and commission rate, compute the estate agent commission and the total with tax, plus the seller's net proceeds. Hong Kong agency commission is generally not subject to VAT.

Student Loan Forgiveness Calculator

Enter the loan amount, annual rate, repayment term, and years paid to compute the remaining balance that could be forgiven after a forgiveness period, plus the amount already paid.

Hardy–Weinberg Equilibrium Calculator

Enter the dominant allele frequency p to instantly compute the genotype frequencies p² (AA), 2pq (Aa), q² (aa) and the dominant/recessive phenotype proportions, with a reference table common in DSE Biology.

Allele Frequency Calculator

Enter the counts of AA, Aa, and aa genotypes to compute dominant and recessive allele frequencies (p and q) and total allele counts, with a population-genetics reference table.

Punnett Square Calculator

Select both parents' genotypes (AA, Aa, or aa) to instantly compute offspring genotype ratios (AA, Aa, aa) and dominant/recessive phenotype ratios, with a reference table of classic Mendelian ratios.

Bacteria Generation Time Calculator

Enter the initial count, final count, and elapsed time to compute the number of generations, generation (doubling) time, and division rate, with a reference table of common bacteria doubling times.

Cell Dilution Calculator

Enter stock concentration, target concentration, and target final volume; the tool uses C₁V₁ = C₂V₂ to find the stock volume, diluent volume, and dilution factor, with a common dilution-factor reference table.

Cell Doubling Time Calculator

Enter the initial and final cell counts (or concentrations) and the elapsed time; the tool computes doubling time, growth rate, and number of doublings, with a reference table of common cell lines.

DNA/RNA Concentration Calculator

Enter the A260 absorbance, nucleic-acid type (dsDNA/ssDNA/RNA), dilution factor, and path length to instantly compute nucleic-acid concentration (μg/mL and ng/μL), with a reference table of common conversion factors.

Protein Concentration Calculator

Enter the 280 nm absorbance, molar extinction coefficient, molecular weight, dilution factor, and path length to compute protein concentration (mg/mL and molar) via the Beer–Lambert law, with a reference table of common proteins.

Log Reduction Calculator

Enter microbial counts before and after treatment to compute log reduction, percent reduction, and surviving fraction, with a 1-log to 6-log reference table.

Mutation Frequency Calculator

Enter the number of mutant colonies and total plated cells to compute mutation frequency (mutants per cell), evaluating mutagenic effects and genetic stability.

Molarity Calculator

Enter solute mass, molar mass and solution volume to instantly compute moles of solute and molarity (mol/L, i.e. M), with a reference table of common reagent molar masses.

PCR Annealing Temperature Calculator

Enter the less-stable primer's melting temperature Tmᵖ and the template Tmᵗ to compute the optimal annealing temperature Ta*, plus a simple Tmᵖ−5 starting reference.

Serial Dilution Calculator

Enter the initial concentration C₀, dilution factor d and number of steps n; using Cₙ = C₀ × dⁿ the tool instantly computes the final concentration after serial dilution and the per-step volume scheme.

DNA Molecular Weight Calculator

Paste a DNA sequence (A/T/C/G/ or IUPAC ambiguous codes); the tool instantly computes molecular weight (MW), base count, length and extinction coefficient, and estimates OD and mass for a given concentration.

DNA Copy Number Calculator

Enter the DNA mass (ng), fragment length (bp), and mass per base pair to compute the number of DNA copies, for qPCR absolute quantification and standard curves.

Cell Density Calculator

Enter the average cell count per large square of a hemocytometer, the dilution factor, and the sample volume; the tool computes cell density (cells/mL) and total cell count, for cell culture and passaging counts.

MOI Calculator

Enter the number of virus particles and the number of host cells to compute the multiplicity of infection (MOI), the average number of virions per cell.

Michaelis–Menten Calculator

Enter maximum velocity Vmax, Michaelis constant Km, and substrate concentration [S] to compute the enzyme-catalyzed reaction rate v and its fraction of Vmax, for enzyme-kinetics analysis.

RNA Copy Number Calculator

Enter RNA mass, nucleotide length, and average molar mass per nucleotide to compute RNA molecule copy number, for qRT-PCR standards and IVT quantification.

OD600 Cell Density Calculator

Enter the optical density at 600 nm (OD600), conversion factor, and culture volume to estimate bacterial cell density (cells/mL) and total cell count, for monitoring bacterial cultures.

GC Content Calculator

Enter the counts of A, T, G, C bases in a DNA sequence to compute the GC percentage and an estimated melting temperature (Tm), for primer design and sequence analysis.

Primer Tm Calculator

Enter the counts of A, T, G, C in a primer to compute the Wallace-rule and salt-corrected (GC%) melting temperature Tm, for PCR primer design.

Enzyme Activity Calculator

Enter the absorbance slope ΔA/min, molar extinction coefficient ε, path length, reaction and sample volumes, and protein concentration to compute enzyme activity (U/mL) and specific activity (U/mg).

Buffer pH Calculator

Enter a weak acid's pKa, conjugate base concentration [A⁻] and weak acid concentration [HA]; using the Henderson–Hasselbalch equation the tool instantly computes the buffer pH and the [A⁻]/[HA] ratio — ideal for preparing buffers.

pH Calculator

Enter [H⁺] (or [OH⁻], or pH/pOH, depending on mode); the tool instantly computes pH, pOH, [H⁺] and [OH⁻], and shows whether the solution is acidic, neutral or basic.

qPCR Efficiency Calculator

Enter the slope of the qPCR standard curve to compute amplification efficiency E = 10^(−1/slope) − 1, evaluating reaction performance and whether the standard curve is ideal.

Water Potential Calculator

Enter solute potential Ψs and pressure potential Ψp to compute total water potential Ψ and determine osmotic water-flow direction, for plant physiology and osmosis study.

Feed Conversion Ratio Calculator

Enter feed intake and weight gain to compute the feed conversion ratio (FCR) and feed efficiency (FE), evaluating how efficiently livestock and aquaculture convert feed into body mass.

Animal Mortality Rate Calculator

Enter deaths and starting total to compute mortality rate, survival rate, and survivor count — for farmed stocks, disease surveillance, and ecological surveys.

Vapor-Pressure-Deficit Calculator

Compute Temperature C, Relative Humidity Pct, Vpd, Saturation Vapor Pressure, Actual Vapor Pressure from Temperature C, Relative Humidity Pct, Vpd, Saturation Vapor Pressure. Free online Hong Kong ecology calculator.

Respiratory Quotient Calculator

Enter CO₂ produced and O₂ consumed to compute the respiratory quotient RQ, judging whether the body or cells burn carbohydrates, protein, or fat as the main fuel.

Surface Area to Volume Ratio Calculator

Enter the cube edge or sphere radius to compute surface area, volume and the SA:V ratio. SA:V = 6/a (cube), 3/r (sphere).

Logistic Growth Calculator

Enter current population, intrinsic growth rate, and carrying capacity to compute the net growth for the next time step and understand the S-shaped (logistic) population curve.

DNA Ligation Calculator

Enter vector mass, vector and insert lengths, and the target molar ratio to compute the insert DNA mass needed for a ligation reaction.

Genotype Frequency Calculator

Enter the counts of AA, Aa, and aa individuals to compute each genotype frequency and the allele frequencies p (A) and q (a) for population-genetics and Hardy–Weinberg analysis.

Generation Time Calculator

Enter the initial count, final count, and elapsed time to compute the number of generations and the generation time (doubling time), assessing bacterial growth rate.

Population-Growth-Rate Calculator

Compute Initial Population, Final Population, Rate Pct, Growth from Initial Population, Final Population, Rate Pct, Growth. Free online Hong Kong ecology calculator.

Net-Primary-Productivity Calculator

Compute Gross Primary Productivity, Respiration, Npp, Efficiency Pct from Gross Primary Productivity, Respiration, Npp, Efficiency Pct. Free online Hong Kong ecology calculator.

Protein Molecular Weight Calculator

Enter the amino-acid residue count and average residue mass; the tool instantly estimates the protein molecular weight (Da and kDa) to quickly read SDS-PAGE bands and sequence size.

Molar Extinction Coefficient Calculator

Enter absorbance A, molar concentration c and path length l; by the Beer–Lambert law the tool instantly computes the molar extinction coefficient ε (M⁻¹·cm⁻¹), used to quantify nucleic acids and proteins.

Daily-Light-Integral Calculator

Compute Ppfd, Light Hours, Dli from Ppfd, Light Hours, Dli. Free online Hong Kong ecology calculator.

Plant Population

Enter field area, plant spacing, row spacing, walkway width and plants per stand to compute total plants and density per m², for seedling demand and yield planning.

Plant Spacing

Enter equal spacing s and field area, choose square or triangular layout, to compute planting density (per m²) and total plants — for planning beds and nursery trays.

Dry Matter Basis Calculator

Enter an as-fed (wet) nutrient percentage and the sample moisture percentage to convert it to a dry-matter basis (DMB%), for fair comparison of feeds, forage and crop nutrition.

Gdu Calculator

Compute Max Temperature, Min Temperature, Base Temperature, Gdu, Mean Temperature from Max Temperature, Min Temperature, Base Temperature, Gdu. Free online Hong Kong ecology calculator.

ET₀ Calculator

Estimate daily reference evapotranspiration ET₀ (mm/day) with the Hargreaves method from daily max/min air temperature and extraterrestrial radiation Ra. Used for irrigation scheduling and crop water demand.

Specific Leaf Area Calculator

Enter leaf area and leaf dry weight to compute specific leaf area SLA = leaf area ÷ leaf dry weight, evaluating how thin and spread the leaf is — a core plant functional trait.

Leaf Area Index (LAI)

Enter total single-side leaf area and the ground area it covers (same unit) to compute the leaf area index LAI = total leaf area ÷ ground area, describing canopy density, light interception and transpiration.

Germination Rate Calculator

Enter the number of germinated seeds and the total sown to compute the germination rate = germinated ÷ sown × 100%, and show the ungerminated count, for evaluating seed quality and sowing amount.

Fertilizer-ppm Calculator

Compute Fertilizer Grams, Nutrient Percent, Water Liters, ppm, Nutrient Mass from Fertilizer Grams, Nutrient Percent, Water Liters, ppm. Free online Hong Kong ecology calculator.

Penman-Monteith Calculator

Compute FAO-56 reference evapotranspiration ET₀ (mm/day) from mean temperature, wind speed, relative humidity, net radiation and soil heat flux. The internationally recognized most accurate crop-water-demand baseline.

SLA / LMA Converter

Choose the conversion direction and enter a value to instantly convert between specific leaf area SLA (cm²/g) and leaf mass per area LMA (g/m²) — reciprocals with area-unit conversion.

Harvest Index (HI)

Enter economic yield (dry weight of the harvested part) and biological yield (total aboveground dry matter) to compute harvest index HI = economic yield ÷ biological yield (0–1 and %), assessing dry-matter allocation efficiency.

NAR Calculator

Enter the plant dry weights, leaf areas at two sampling times, and the interval in days to compute the net assimilation rate (NAR), the dry-matter gain per unit leaf area per unit time — a core growth-analysis metric.

Par-To-Dli Calculator

Compute Ppfd, Photoperiod Hours, Dli from Ppfd, Photoperiod Hours, Dli. Free online Hong Kong ecology calculator.

Irrigation Water Requirement

Enter crop water need ETc, effective rainfall, irrigation efficiency and field area to compute net and gross irrigation depth and the actual supply volume (m³ and litres) for scheduling and water planning.

Seeding Rate

Enter target plant density, thousand-grain weight and germination rate to compute target plants/ha, seeds/ha and seed rate (kg/ha) for sowing planning and seed purchase.

Water Use Efficiency (WUE)

Enter yield (kg/ha) and seasonal water depth (mm) to compute water volume per hectare and water use efficiency WUE = yield ÷ volume (kg/m³), assessing irrigation output efficiency.

Grain-Moisture-Yield Calculator

Compute Measured Yield, Measured Moisture Pct, Standard Moisture Pct, Adjusted Yield, Dry Matter Yield from Measured Yield, Measured Moisture Pct, Standard Moisture Pct, Adjusted Yield. Free online Hong Kong ecology calculator.

Soil-Water-Storage Calculator

Compute Field Capacity Pct, Wilting Point Pct, Root Depth cm, Available Water mm from Field Capacity Pct, Wilting Point Pct, Root Depth cm, Available Water mm. Free online Hong Kong ecology calculator.

Crop Water Requirement (Kc)

Enter crop coefficient Kc, reference evapotranspiration ET₀ and stage days to compute daily crop evapotranspiration ETc and cumulative stage water requirement (mm and m³/ha) for irrigation planning.

Plant-Spacing-Density Calculator

Compute Direction, Row Spacing, Plant Spacing Or Density, Plants per Hectare, Plant Spacing, Plants per Square Meter, Area per Plant from Direction, Row Spacing, Plant Spacing Or Density, Plants per Hectare. Free online Hong Kong ecology calculator.

Nitrogen Fertilizer Requirement

Enter target nitrogen supply, fertilizer N content (%) and field area to compute the actual fertilizer amount per hectare and for the whole field (kg), for fertilization planning and cost estimation.

Irrigation Interval

Enter root-zone available water, management allowable depletion MAD and daily crop evapotranspiration ETc to compute usable water and the days between irrigations for scheduling.

Transpiration Rate Calculator

Enter water loss, leaf area, and time to compute the transpiration rate (g·m⁻²·h⁻¹) and convert it to mmol·m⁻²·s⁻¹, quantifying leaf water loss intensity.

Kc-Staged-Water-Need Calculator

Compute Reference Et0, Kc Initial, Days Initial, Kc Development, Days Development, Kc Mid, Days Mid, Kc Late, Days Late, Total mm, Total Cubic Meter per Hectare, Total Days from Reference Et0, Kc Initial, Days Initial, Kc Development. Free online Hong Kong ecology calculator.

Net Photosynthesis Calculator

Enter gross (total) photosynthesis and respiration to compute net photosynthesis Pn = Pg − Rd, quantifying the actual carbon assimilation after subtracting respiration.

Fertigation-Stock Calculator

Compute Stock Gram per Liter, Injection Ratio X, Diluted ppm, Diluted Gram per Liter from Stock Gram per Liter, Injection Ratio X, Diluted ppm, Diluted Gram per Liter. Free online Hong Kong ecology calculator.

Relative Growth Rate Calculator

Enter the initial and final dry weights and the time interval to compute relative growth rate RGR = (ln W₂ − ln W₁) / (t₂ − t₁), evaluating the daily dry-matter gain per unit existing dry weight.

Crop Yield Estimate Calculator

Enter plants per hectare and yield per plant (g) to estimate yield per hectare (kg/ha and t/ha). Useful for pre-harvest yield forecasting and planting planning.

Par-Interception Calculator

Compute Incident Par, Extinction Coefficient, Leaf Area Index, Interception Pct, Intercepted Par, Transmitted Fraction from Incident Par, Extinction Coefficient, Leaf Area Index, Interception Pct. Free online Hong Kong ecology calculator.

Root-Shoot-Ratio Calculator

Compute Root Dry Weight, Shoot Dry Weight, Ratio, Total Biomass, Root Fraction Pct from Root Dry Weight, Shoot Dry Weight, Ratio, Total Biomass. Free online Hong Kong ecology calculator.

Seed Vigor Index Calculator

Enter germination percentage and mean seedling length to compute the seed vigor index SVI = germination(%) × seedling length(cm) by the Abdul-Baki & Anderson method, assessing seed-batch vigor and quality.

Chlorophyll Content Calculator

Enter the SPAD reading and the calibration curve slope and intercept; by the linear model chlorophyll = slope × SPAD + intercept the tool estimates leaf chlorophyll content, to assess crop nitrogen status and growth.

Growing Degree Days (GDD)

Enter daily max/min temperature, crop base temperature and days to compute daily mean, daily GDD and accumulated GDD over the period, for predicting crop phenology and growth stages.

Leaf Area Ratio Calculator

Enter total leaf area and total plant dry weight to compute the leaf area ratio LAR = total leaf area ÷ total dry weight, evaluating how efficiently biomass is invested in light-catching foliage.

Specific Growth Rate Calculator

Enter initial and final cell counts (or concentrations) and the time interval to compute specific growth rate μ = ln(N₂/N₁) ÷ Δt and doubling time td = ln2 ÷ μ, quantifying exponential-phase microbial proliferation.

Nutrient-Use-Efficiency Calculator

Compute Crop Yield, Nutrient Applied, Nue from Crop Yield, Nutrient Applied, Nue. Free online Hong Kong ecology calculator.

Crop-Growth-Rate Calculator

Compute Initial Weight, Final Weight, Ground Area, Days, Cgr, Biomass Gain from Initial Weight, Final Weight, Ground Area, Days. Free online Hong Kong ecology calculator.

Crop Water Footprint

Enter total water use and crop yield to compute the crop water footprint = water use (m³) ÷ yield (t), with the equivalent L/kg, assessing water-resource efficiency of production.

Specific Root Length Calculator

Enter root length and root dry weight to compute specific root length SRL = root length ÷ root dry weight, evaluating root 'thinness' and the soil-exploration efficiency per unit biomass.

C/N Ratio Calculator

Enter carbon and nitrogen contents (same unit) to compute the carbon-to-nitrogen ratio C/N = carbon ÷ nitrogen, used for compost mix, organic-matter decomposition rate, and soil nitrogen immobilization or release.

Transpiration Efficiency Calculator

Enter accumulated dry matter and transpired water to compute transpiration efficiency TE = dry matter ÷ transpiration, assessing how much dry matter a plant produces per unit water lost.

Stomatal Conductance Calculator

Enter transpiration rate and the leaf-to-air water vapor mole-fraction difference to compute stomatal conductance gs = E ÷ Δw, for quantifying stomatal aperture and plant water/gas-exchange status.

Salinity (EC) Calculator

Enter the electrical conductivity (EC) of soil or irrigation water and a conversion factor; the tool instantly estimates total dissolved solids TDS (mg/L = ppm) and salt content (g/L) to assess water quality and salt-stress risk.

Relative Water Content Calculator

Enter fresh weight, dry weight, and turgid (saturated) weight to compute relative water content RWC = (Fresh − Dry) ÷ (Turgid − Dry) × 100%, quantifying leaf water deficit and drought tolerance.

Thousand-Grain-Weight Calculator

Compute Sample Weight, Seed Count, Tgw from Sample Weight, Seed Count, Tgw. Free online Hong Kong ecology calculator.

Root-Length-Density Calculator

Compute Root Length, Soil Volume, Rld from Root Length, Soil Volume, Rld. Free online Hong Kong ecology calculator.

Leaf Mass Fraction Calculator

Enter leaf dry weight and total plant dry weight to compute the leaf mass fraction LMF = leaf dry weight ÷ total dry weight (with percentage), evaluating the share of biomass allocated to leaves.

Osmotic Potential Calculator

Enter solute molarity, temperature, and dissociation coefficient to compute osmotic (solute) potential Ψs = −iCRT (MPa) via the van't Hoff equation, estimating a solution's water-attracting strength.

Bulk Density to Porosity Calculator

Enter soil bulk density and particle density to compute total porosity (%) = (1 − bulk density ÷ particle density) × 100, assessing soil looseness, aeration, and water retention.

Available Water Capacity Calculator

Enter field capacity, permanent wilting point, and root-zone depth to compute available water capacity AWC (%vol) = FC − PWP and the usable stored water depth (mm) for irrigation planning and soil water interpretation.

Distribution-Uniformity Calculator

Compute Low Quarter Average, Overall Average, Du Pct from Low Quarter Average, Overall Average, Du Pct. Free online Hong Kong ecology calculator.

Effective-Rainfall Calculator

Compute Rainfall mm, Factor, Eff Rain mm from Rainfall mm, Factor, Eff Rain mm. Free online Hong Kong ecology calculator.

Field-Capacity Calculator

Compute Gravimetric Pct, Bulk Density, Depth mm, Volumetric Pct, Storage mm from Gravimetric Pct, Bulk Density, Depth mm, Volumetric Pct. Free online Hong Kong ecology calculator.

Infiltration-Rate Calculator

Compute K, A, Time Minutes, Cum Infiltration, Infiltration Rate from K, A, Time Minutes, Cum Infiltration. Free online Hong Kong ecology calculator.

Water-Productivity Calculator

Compute Yield Amount, Water Used, Wp from Yield Amount, Water Used, Wp. Free online Hong Kong ecology calculator.

Leaching-Requirement Calculator

Compute Ecw, Ece, Lr, Lr Pct from Ecw, Ece, Lr, Lr Pct. Free online Hong Kong ecology calculator.

Irrigation Efficiency

Enter water stored in the root zone and water actually applied to compute irrigation efficiency = (stored ÷ applied) × 100%, assessing system water loss and improvement room.

Crop Water Stress Index (CWSI)

Enter measured canopy-air temperature difference dT and the well-watered lower baseline dT_ll and non-transpiring upper baseline dT_ul to compute CWSI = (dT − dT_ll) ÷ (dT_ul − dT_ll), judging water-deficit level and irrigation timing.

Christiansen Uniformity Calculator

Enter four measurement-point application depths; the tool computes Christiansen's uniformity coefficient CU = 100·(1 − Σ|xᵢ−x̄| ÷ (n·x̄)), assessing sprinkler/micro-irrigation water uniformity.

Soil-Organic-Carbon Calculator

Compute Soc Pct, Bulk Density, Depth cm, Stock T per ha from Soc Pct, Bulk Density, Depth cm, Stock T per ha. Free online Hong Kong ecology calculator.

Canopy Cover Calculator

Enter single-plant canopy diameter, row spacing, and plant spacing to compute canopy cover % = circular canopy projection area ÷ (row spacing × plant spacing) × 100%, assessing shading, light interception, and ground cover.

Water-Holding-Capacity Calculator

Compute Field Capacity Volume Pct, Depth mm, Storage mm from Field Capacity Volume Pct, Depth mm, Storage mm. Free online Hong Kong ecology calculator.

Chilling Hours Accumulation Calculator

Enter daily chill hours, number of days, and the cultivar's chilling requirement; the tool computes accumulated chilling = avg daily chill hours × days, and fulfillment = accumulated ÷ requirement × 100%, judging whether a deciduous tree can break dormancy normally.

Management-Allowed-Depletion Calculator

Compute Field Capacity, Wilting Point, Root Depth mm, Mad Fraction, Raw mm, Taw mm from Field Capacity, Wilting Point, Root Depth mm, Mad Fraction. Free online Hong Kong ecology calculator.

Sodium-Adsorption-Ratio Calculator

Compute Sodium, Calcium, Magnesium, Sar from Sodium, Calcium, Magnesium, Sar. Free online Hong Kong ecology calculator.

Spray-Application-Rate Calculator

Compute Nozzle Flow, Speed, Nozzle Spacing, Liters per ha from Nozzle Flow, Speed, Nozzle Spacing, Liters per ha. Free online Hong Kong ecology calculator.

Dew Point Temperature

Enter air temperature and relative humidity to compute dew-point temperature Td with the Magnus formula, for judging condensation, frost risk and leaf-wetness disease timing.

Agronomic Nitrogen Efficiency Calculator

Enter nitrogen-treated yield, zero-N control yield, and N rate to compute the Agronomic Efficiency of N: AEN = (Yn − Y0) ÷ F, i.e. how much extra yield per kg of N.

Crop-Residue-Carbon Calculator

Compute Residue Dry Mass, Carbon Fraction, Carbon from Residue Dry Mass, Carbon Fraction, Carbon. Free online Hong Kong ecology calculator.

Base Saturation Calculator

Enter exchangeable Ca, Mg, K, Na and cation exchange capacity CEC to compute base saturation BS% = (sum of bases ÷ CEC) × 100, assessing soil fertility and acidification.

Exchangeable-Sodium-Percentage Calculator

Compute Exchangeable Sodium, Cec, Esp Pct from Exchangeable Sodium, Cec, Esp Pct. Free online Hong Kong ecology calculator.

Soil-Carbon-Stock Calculator

Compute Soc Pct, Bulk Density, Depth cm, Gravel Fraction, Stock T per ha from Soc Pct, Bulk Density, Depth cm, Gravel Fraction. Free online Hong Kong ecology calculator.

Soil Loss (USLE)

Enter rainfall erosivity R, soil erodibility K, slope-length-steepness LS, cover-management C and support-practice P to compute annual soil loss A = R×K×LS×C×P (t/ha/yr).

Lime-Requirement Calculator

Compute Current pH, Target pH, Lime per Unit pH, Lime T per ha from Current pH, Target pH, Lime per Unit pH, Lime T per ha. Free online Hong Kong ecology calculator.

Gypsum-Requirement Calculator

Compute Initial Esp, Target Esp, Cec, Bulk Density, Depth cm, Gypsum T per ha from Initial Esp, Target Esp, Cec, Bulk Density. Free online Hong Kong ecology calculator.

Soil-Water-Deficit Calculator

Compute Field Capacity, Current Moisture, Root Depth mm, Deficit mm from Field Capacity, Current Moisture, Root Depth mm, Deficit mm. Free online Hong Kong ecology calculator.

Nitrogen-Mineralization Calculator

Compute Organic Matter kg ha, Nitrogen Fraction, Mineralization Rate, Total Organic N, Mineralized N from Organic Matter kg ha, Nitrogen Fraction, Mineralization Rate, Total Organic N. Free online Hong Kong ecology calculator.

Soil Cation Ratio

Enter exchangeable Ca, Mg, K (cmol(+)/kg) to compute the Ca:Mg and Mg:K ratios, assessing base balance and nutrient antagonism risk.

Runoff Curve Number (CN)

Enter rainfall and curve number CN to compute potential retention S, initial abstraction Ia and runoff Q (SCS-CN method), estimating storm runoff.

Crop Yield Response to Water (Ky)

Enter yield response factor Ky, actual evapotranspiration ETa and maximum ETm to compute evapotranspiration deficit, relative yield loss and relative yield (FAO-33 Ky model), assessing drought impact on crops.

Soil-Temperature-Depth Calculator

Compute Surface Amplitude, Depth, Damping Depth, Amplitude At Depth, Phase Lag Rad, Phase Lag Fraction Of Period from Surface Amplitude, Depth, Damping Depth, Amplitude At Depth. Free online Hong Kong ecology calculator.

Farm Drainage Discharge Calculator

Enter the drainage coefficient (mm/day) and farm area (ha) to compute daily discharge Q = coefficient × area × 10 (m³/day) and L/s for drainage design.

Soil-Heat-Flux Calculator

Compute Thermal Conductivity, Surface Temperature, Depth Temperature, Depth m, Heat Flux Wm2 from Thermal Conductivity, Surface Temperature, Depth Temperature, Depth m. Free online Hong Kong ecology calculator.

Readily-Available-Water Calculator

Compute Field Capacity, Wilting Point, Root Depth m, Depletion Fraction, Total Available Water mm, Readily Available Water mm from Field Capacity, Wilting Point, Root Depth m, Depletion Fraction. Free online Hong Kong ecology calculator.

Blaney–Criddle Calculator

Enter the daytime-hour factor p and the mean temperature T to compute the Blaney–Criddle reference evapotranspiration ET = p × (0.46T + 8.13) (mm/day), estimating crop water need from temperature and daylight only.

Priestley-Taylor Calculator

Compute Alpha, Slope Delta, Psychrometric Gamma, Available Energy, Delta Factor, Et from Alpha, Slope Delta, Psychrometric Gamma, Available Energy. Free online Hong Kong ecology calculator.

Capillary Rise Calculator

Compute capillary rise h = 2σcosθ/(ρgr) in a tube.

Leaf Water Potential Calculator

Enter osmotic potential Ψs (usually negative) and pressure potential Ψp (usually positive) to compute total leaf water potential Ψ = Ψs + Ψp (MPa), assessing plant water status and drought stress.

Darcy's Law (Flux) Calculator

Compute Darcy flux and volumetric flow from K, gradient and area.

Manning Flow Calculator

Enter Manning n, hydraulic radius, slope and flow area to compute the open-channel velocity and discharge via Manning's equation.

Saturation-Vapor-Pressure Calculator

Compute Temperature C, Saturation Vapor Pressure from Temperature C, Saturation Vapor Pressure. Free online Hong Kong ecology calculator.

Relative Humidity

Enter air temperature and dew-point, compute relative humidity RH = es(dew)/es(temp) × 100% via the Tetens saturation vapor-pressure formula, plus actual and saturation vapor pressure.

Falling Head Conductivity Calculator

Enter standpipe area, sample geometry, time and head levels to compute hydraulic conductivity via the falling-head (constant-head) test.

Rectangular Weir Discharge Calculator

Enter the discharge coefficient C, crest width L and head H to compute flow over a rectangular weir from Q=C·L·H^(3/2) (m³/s), used for irrigation and open-channel flow measurement.

Orifice Discharge Calculator

Enter discharge coefficient, orifice area and head to compute the discharge Q = C_d·A·√(2·g·h).

Hazen–Williams Calculator

Estimate head loss in a pipe using the Hazen–Williams empirical formula.

Pipe Reynolds Number Calculator

Enter velocity, diameter and kinematic viscosity to compute the pipe-flow Reynolds number Re = v·D/ν.

Psychrometric-Constant Calculator

Compute Atmospheric Pressure, Latent Heat, Psychrometric Constant from Atmospheric Pressure, Latent Heat, Psychrometric Constant. Free online Hong Kong ecology calculator.

Chézy Flow Calculator

Compute open-channel velocity v = C·√(R·S) (Chézy formula).

Froude Number Calculator

Compute the Froude number Fr = v/√(gL).

Specific Energy Calculator

Enter flow depth y and mean velocity v to compute specific energy E=y+v²/(2g) (channel bottom as datum). y=0.5 m, v=2 m/s → E≈0.704 m. Key to critical flow and open-channel transitions.

Hydraulic Radius Calculator

Enter channel bottom width and depth to compute the hydraulic radius R = A/P for a rectangular open channel.

Critical Depth Calculator

Compute the critical depth y_c of open-channel flow (minimum specific energy).

Normal Depth Calculator

Enter discharge, bottom width, Manning roughness and slope to compute the normal depth of a rectangular open channel by inverse Manning's formula.

Weber Number Calculator

Enter density, velocity, length and surface tension to compute the Weber number We=ρv²L/σ. ρ=998, v=1, L=0.1, σ=0.0728 → We≈1371 (inertia dominates, droplet shatters).

Hydraulic Jump Calculator

Enter the upstream depth and Froude number to compute the conjugate (sequent) downstream depth of a hydraulic jump.

Manning–Chezy Calculator

Enter Manning roughness n and hydraulic radius R to compute the Chezy coefficient C = R^(1/6)/n.

Open Channel Reynolds Number Calculator

Enter velocity, hydraulic radius and kinematic viscosity to compute the Reynolds number Re = v·R/ν for open-channel flow.

Torricelli's Law Calculator

Enter the head h above an orifice to compute the ideal exit velocity v=√(2gh). h=2 m → v≈6.264 m/s; doubling the head only multiplies v by √2 (≈1.41×).

Velocity Head Calculator

Enter flow velocity to compute velocity head h_v=v²/(2g), the kinetic-energy term of Bernoulli's equation. v=3 m/s → h_v≈0.459 m; double the speed → 4× the head.

Volumetric Flow Rate Calculator

Enter cross-sectional area and average velocity to compute volumetric flow rate Q=A·v. A=0.05 m², v=2 m/s → Q=0.1 m³/s (=100 L/s). For pipes, channels and irrigation.

Darcy Friction Factor Calculator

Estimate the Darcy friction factor from Reynolds number (approx).

Stokes Settling Velocity Calculator

Enter the particle diameter d, the particle and fluid densities and the dynamic viscosity μ to compute the terminal settling velocity from v_s = g·d²·(ρp−ρf)/(18μ).

Water Hammer Calculator

Enter fluid density, pressure-wave speed and velocity change to compute the water-hammer pressure rise Δp=ρaΔv and head Δh. ρ=1000, a=1200, Δv=2 → Δp=2.4 MPa (~245 m head).

Rectangular Weir Calculator

Enter discharge coefficient, crest width and head to compute flow Q=(2/3)Cd·b·√(2g)·H^1.5. Cd=0.62, b=1 m, H=0.3 m → Q≈0.301 m³/s (301 L/s).

Triangular (V-Notch) Weir Calculator

Enter the discharge coefficient Cd, notch angle θ and head H to compute the flow of a triangular (V-notch) weir from Q = (8/15)·Cd·tan(θ/2)·√(2g)·H^(5/2).

Seepage Velocity Calculator

Enter hydraulic conductivity, hydraulic gradient and effective porosity to compute seepage velocity v=K·i/n. K=1e-5, i=0.01, n=0.3 → v=3.33e-7 m/s. Groundwater actually moves far slower than Darcy flux.

Specific Force Calculator

Enter unit discharge q and depth y to compute specific force M=q²/(gy)+y²/2 (rectangular channel, per unit width). q=2, y=1 → M≈0.908 m³/m. Core to hydraulic jumps and conjugate depths.

Swamee-Jain Friction Factor Calculator

Enter pipe roughness ε, diameter D and Reynolds number Re to compute the Darcy friction factor from the explicit Swamee-Jain formula, avoiding iterative Colebrook solving.

Minor Loss Calculator

Enter the loss coefficient and flow velocity to compute the minor (local) head loss in a pipe fitting.

Pump Hydraulic Power Calculator

Enter fluid density, flow rate and head to compute the hydraulic power P = ρ·g·Q·H required by a pump.

Shallow-Water Wave Celerity Calculator

Enter water depth y to compute the propagation speed of shallow-water (long) gravity waves from c=√(g·y), the basis of open-channel flow regimes and the Froude number.

Drag Force Calculator

Enter drag coefficient Cd, fluid density ρ, frontal area A and relative velocity v to compute the fluid drag force Fd = ½·Cd·ρ·A·v².

Terminal Velocity Calculator

Find terminal velocity v=√(2mg/(ρ·A·Cd)). Enter mass, gravity, air density, area and drag coefficient. Skydiver (~80 kg) ≈ 55 m/s.

Pitot Tube Velocity Calculator

Enter stagnation (dynamic) pressure and fluid density to compute the flow velocity v = √(2·Δp/ρ).

Hydraulic Jump Energy Loss Calculator

Enter upstream and downstream depths of a hydraulic jump to compute the specific-energy loss.

Boundary Layer Thickness Calculator

Estimate laminar boundary layer thickness δ ≈ 5x/√Re.

Kinetic Energy Calculator

Compute kinetic energy KE = ½mv².

Gravitational Potential Energy Calculator

Enter mass and height to compute gravitational potential energy U = m·g·h.

Momentum Calculator

Enter mass and velocity to compute linear momentum p = m·v.

Hydrostatic Pressure Calculator

Enter fluid density and depth to compute the hydrostatic pressure p = ρ·g·h.

Buoyancy Calculator

Compute buoyant force from fluid density and displaced volume (Archimedes).

Mach Number Calculator

Enter flow speed and the speed of sound to compute the Mach number M = v/a.

Reynolds Number Calculator

Enter fluid density ρ, velocity v, characteristic length L and dynamic viscosity μ to compute Re=ρvL/μ and judge laminar vs turbulent flow. Water 1000, 1 m/s, 0.1 m, 0.001 → Re=100,000 (turbulent).

Darcy–Weisbach Calculator

Compute head loss h_f = f·(L/D)·v²/(2g) in a pipe.

Dynamic Pressure Calculator

Compute dynamic pressure q = ½ρv².

Capillary Number Calculator

Compute the capillary number Ca = μv/σ (viscous vs surface tension).

Stagnation Pressure Calculator

Enter static pressure, density and velocity to compute stagnation (total) pressure p₀=p+½ρv². Air p=101325 Pa, ρ=1.225, v=50 m/s → p₀≈102856 Pa. The basis of the Pitot tube.

Prandtl Number Calculator

Enter dynamic viscosity, specific heat and thermal conductivity to compute the Prandtl number Pr = μ·c_p/k.

Nusselt Number Calculator

Enter heat-transfer coefficient, characteristic length and thermal conductivity to compute the Nusselt number Nu = h·L/k.

Fourier's Law of Heat Conduction Calculator

Enter thermal conductivity, area, temperature difference and thickness to compute the conductive heat rate q = k·A·ΔT/L.

Stefan-Boltzmann Law Calculator

Enter emissivity ε, area A and absolute temperature T to compute radiated power P=ε·σ·A·T⁴. ε=0.9, A=1 m², T=300 K → P≈413 W. T in Kelvin.

Thermal Diffusivity Calculator

Enter thermal conductivity, density and specific heat to compute thermal diffusivity α=k/(ρ·c_p). Water k=0.6, ρ=1000, c_p=4182 → α≈1.435e-7 m²/s; copper ≈1.1e-4 (≈800× faster).

Grashof Number Calculator

Compute the Grashof number Gr = gβΔTL³/ν² (buoyancy vs viscosity).

Rayleigh Number Calculator

Enter Grashof and Prandtl numbers to compute Rayleigh number Ra=Gr·Pr=g·β·ΔT·L³/(ν·α). Air: Gr≈2.65×10⁶, Pr≈0.7 → Ra≈1.86×10⁶ (laminar natural convection).

Schmidt Number Calculator

Enter kinematic viscosity and mass diffusivity to compute the Schmidt number Sc=ν/D. Air-water vapour ν=1.57e-5, D=2.5e-5 → Sc≈0.63; water-CO₂ ν=1e-6, D=1.9e-9 → Sc≈526.

Lewis Number Calculator

Enter thermal and mass diffusivities to compute the Lewis number Le = α/D (ratio of thermal to mass diffusion).

Biot Number Calculator

Compute the Biot number Bi = h·L/k for heat transfer.

Stanton Number Calculator

Enter the Nusselt number Nu, Reynolds number Re and Prandtl number Pr to compute the Stanton number from St = Nu/(Re·Pr), a measure of convective heat transfer intensity.

Péclet Number Calculator

Enter velocity, characteristic length and thermal/mass diffusivity to compute the Péclet number Pe = v·L/D.

Sherwood Number Calculator

Enter mass-transfer coefficient, characteristic length and mass diffusivity to compute the Sherwood number Sh=k·L/D. k=1e-4, L=0.05, D=1e-9 → Sh=5000 (high mass transfer).

Fourier Number Calculator

Enter thermal diffusivity, time and characteristic length to compute the dimensionless Fourier number Fo = α·t/L².

Jakob Number Calculator

Enter specific heat, temperature difference and latent heat to compute the Jakob number Ja = c_p·ΔT/h_fg.

Ohnesorge Number Calculator

Enter viscosity, density, surface tension and length to compute the Ohnesorge number Oh = μ/√(ρ·σ·L).

Bond Number Calculator

Compute the Bond number Bo = ρgL²/σ (gravity vs surface tension).

Euler Number Calculator

Enter pressure drop, density and velocity to compute the Euler number Eu = Δp/(ρ·v²), a dimensionless fluid-dynamics ratio.

Damköhler Number Calculator

Compute the Damköhler number Da = k·τ (reaction vs residence time).

Knudsen Number Calculator

Compute the Knudsen number Kn = λ/L (mean free path / scale).

Carbon Footprint Calculator

Enter an activity amount (e.g. electricity kWh) and the corresponding emission factor to compute the carbon footprint CF = activity × emission factor (kg CO₂e), quantifying greenhouse-gas emissions of that activity.

Shannon-Diversity Calculator

Compute N1, N2, N3, N4, Shannon, Evenness from N1, N2, N3, N4. Free online Hong Kong ecology calculator.

Rainwater Harvesting

Enter catchment area, rainfall and runoff coefficient to compute collectible rainwater V = area × rainfall × runoff coefficient (litres and m³), estimating rainwater-recycling potential.

Tree Carbon Sequestration

Enter tree dry biomass and carbon fraction to compute carbon stock (C = biomass × fraction) and CO₂ equivalent (CO₂ = C × 44/12), assessing a tree's carbon contribution.

Biochemical Oxygen Demand Calculator

Enter the dissolved oxygen before and after incubation and the dilution factor to compute biochemical oxygen demand BOD = (DO_initial − DO_final) × dilution factor (mg/L), assessing organic pollution.

Snell's Law Calculator

Compute refraction or incidence angle from n₁, n₂ and one angle. n₁sinθ₁=n₂sinθ₂. Air→water: 30°→22°; total internal reflection when angle exceeds critical angle.

Escape Velocity Calculator

Enter a celestial body's mass and radius to compute its escape velocity v = √(2GM/r).

Hooke's Law Calculator

Enter spring constant and displacement to compute the spring force F = −k·x and its elastic potential energy.

Ohm's Law Calculator

From current and resistance compute voltage and power (V=IR, P=I²R).

Coulomb's Law Calculator

Compute the electrostatic force F = kq₁q₂/r² between two charges.

Newton's Second Law Calculator

Enter mass and acceleration to compute the net force F = m·a instantly.

Gravitational Force Calculator

Compute Newton's gravitational force F = Gm₁m₂/r².

Wave Speed Calculator

Enter frequency and wavelength to find wave speed v=f·λ. f=440 Hz, λ=0.78 m → v≈343 m/s (speed of sound in air).

Specific Heat Calculator

Enter mass, specific heat capacity and temperature change to compute heat Q=m·c·ΔT. 2 kg water (c=4186) +30 K → 251,160 J. Also solves c, m, ΔT.

Pendulum Period Calculator

Enter length and gravity to compute the small-angle pendulum period T = 2π·√(L/g).

Power Calculator

Enter work and time (or force and velocity) to compute power P = W/t = F·v.

Density Calculator

Compute density ρ = m/V from mass and volume.

Torque Calculator

Enter force, lever distance and angle to compute torque τ=r·F·sinθ. F=20 N, r=0.5 m, θ=90° → τ=10 N·m; at 30° → 5 N·m.

Centripetal Force Calculator

Compute centripetal force F = mv²/r = mω²r.

Impulse-Momentum Calculator

Enter force, time, mass and initial velocity to compute impulse and final velocity via J = Δp = F·Δt = m·Δv.

Angular Velocity Calculator

Compute angular velocity ω = θ/t and the related linear velocity.

Work Done Calculator

Enter the force, displacement and angle to compute the work W=F·d·cosθ, quantifying the energy transferred by a force. Pushing 50 N over 3 m (same direction) → W=150 J.

Efficiency Calculator

Compute efficiency η = useful output / total input.

Electric Field Calculator

Compute electric field E = kq/r² from a point charge.

Photon Energy Calculator

Enter frequency or wavelength to compute photon energy E = h·f = h·c/λ (in joules and eV).

Latent Heat Calculator

Compute heat Q = m·L for a phase change.

Ideal Gas Law Calculator

Enter any three of moles, temperature, volume and pressure to compute the fourth via PV = nRT.

Capacitor Energy Calculator

Compute energy stored in a capacitor E = ½CV² = Q²/(2C).

de Broglie Wavelength Calculator

Compute λ = h/(mv) for a particle (alt units).

Decibel Calculator

Convert between ratio and decibels: dB = 10·log10(P₂/P₁) or 20·log10(V₂/V₁).

Dilution Calculator

Enter the stock concentration, target concentration and target volume; using C₁V₁ = C₂V₂ the tool instantly computes the required stock (concentrate) volume, the solvent (water) volume to add and the dilution factor.

Percent Yield Calculator

Enter the actual yield from the experiment and the theoretical yield from stoichiometry; using %yield = (actual / theoretical) × 100% the tool instantly computes the percent yield of a reaction.

Mass Percent Calculator

Compute the mass percent (w/w%) of a solute in a solution from solute and solution masses.

Radioactive Decay Calculator

Enter the initial amount N₀, half-life T½ and elapsed time t; using N = N₀·(½)^(t/T½) the tool instantly computes the remaining amount and activity and the decayed fraction.

Arrhenius Equation Calculator

Enter the pre-exponential factor A, activation energy Ea, and absolute temperature T to compute the reaction rate constant k = A·e^(−Ea/RT).

Moles to Grams Calculator

Enter the amount of substance (moles) and the molar mass; using m = n·M the tool instantly computes the mass (grams) of solute or reagent needed — the basis of solution prep and stoichiometry.

Percent Composition Calculator

Enter an element's total mass within one mole of the compound and the compound molar mass; the tool instantly computes the mass percent composition (element% = element mass ÷ compound molar mass × 100%).

Boyle's Law Calculator

Enter initial pressure, initial volume and final pressure to instantly compute the final gas volume under Boyle's law P₁V₁ = P₂V₂ at constant temperature.

Combined Gas Law Calculator

Enter the initial and final pressure, temperature, and initial volume; by the combined gas law P₁V₁/T₁ = P₂V₂/T₂ it instantly computes the gas volume in the new state for a fixed amount of gas.

Gibbs Free Energy Calculator

Enter the enthalpy change ΔH, absolute temperature T and entropy change ΔS; using ΔG = ΔH − TΔS the tool instantly computes the Gibbs free-energy change and judges whether the reaction is spontaneous at that temperature.

Average Reaction Rate Calculator

Enter the initial and final concentrations and the time interval; using rate = |ΔC|/Δt the tool instantly computes the average reaction rate over that period.

First-Order Half-Life Calculator

Enter the first-order rate constant k; using t½ = ln2 / k the tool instantly computes the half-life — the time required for the reactant concentration to halve.

Atom Economy Calculator

Enter the molar mass of the desired product and the total molar mass of reactants to compute atom economy: AE% = desired product ÷ total reactants × 100%.

Percent Error Calculator

Enter the experimental (measured) value and the theoretical (true) value; using %error = |E − T| / |T| × 100% the tool instantly computes the percent error of an experimental result.

Osmotic Pressure Calculator

Enter the van't Hoff factor i, molarity M and absolute temperature T; by the van't Hoff equation Π = i·M·R·T the tool instantly computes the osmotic pressure (atm and kPa).

Charles's Law Calculator

Enter the initial volume, initial temperature, and final temperature; by Charles's law V₁/T₁ = V₂/T₂ the tool computes the gas final volume at constant pressure.

Gay-Lussac's Law Calculator

Enter the initial pressure, initial temperature and final temperature; by Gay-Lussac's law P₁/T₁ = P₂/T₂ the tool instantly computes the final gas pressure at constant volume.

Grams to Moles Calculator

Enter the mass m in grams and the molar mass M (g/mol); using n = m / M the tool instantly converts grams to moles, a basic everyday step in stoichiometry.

Avogadro's Law Calculator

Enter the initial volume, initial amount of substance, and final amount of substance to compute the final gas volume at constant temperature and pressure via V₁/n₁ = V₂/n₂.

Equilibrium Constant Calculator

Enter the equilibrium concentrations and stoichiometric coefficients of each species in aA + bB ⇌ cC + dD; using Kc = ([C]^c·[D]^d)/([A]^a·[B]^b) the tool instantly computes the equilibrium constant.

Freezing Point Depression Calculator

Enter the van't Hoff factor i, cryoscopic constant Kf, molality b and the pure-solvent freezing point; using ΔTf = i·Kf·b the tool computes the freezing-point depression and the solution freezing point.

Boiling-Point Elevation Calculator

Enter the van't Hoff factor i, ebullioscopic constant Kb, molality b, and pure-solvent boiling point to compute the boiling-point elevation ΔTb = i·Kb·b and the solution boiling point.

Molality Calculator

Enter the solute moles and the solvent mass (kg); using b = n_solute / m_solvent the tool instantly computes the molality (mol/kg) of the solution.

Normality Calculator

Enter the moles of solute, the equivalence factor and the solution volume; using N = (moles × factor)/V the tool instantly computes the normality (eq/L).

Mole Fraction Calculator

Enter the moles of each component; using xᵢ = nᵢ / Σn the tool instantly computes each component's mole fraction, which always sums to 1.

STP Gas Moles Calculator

Enter the gas volume (L) at standard temperature and pressure (STP, 0 °C, 1 atm); by n = V / 22.414 the tool instantly computes the moles of gas.

Solution Density Calculator

Enter the mass (g) and volume (mL) of a solution or substance; by ρ = m/V the tool instantly computes the density (g/mL).

PPM Concentration Calculator

Enter the solute mass and total solution mass (same unit); using ppm = (solute / solution) × 10⁶ the tool instantly computes the parts-per-million concentration.

Molar Mass Calculator

Enter a chemical formula; the tool instantly computes the molar mass M = Σ(atomic mass × atom count) from atomic weights, and also reports element composition and percentage by mass.

Theoretical Yield Calculator

Enter the limiting-reagent moles, the stoichiometric ratio (product coefficient / limiting-reagent coefficient) and the product molar mass; the tool instantly computes the product moles and theoretical mass.

Titration Calculator

Enter the known solution's concentration C₁ and volume V₁ and the unknown solution's volume V₂; at the equivalence endpoint (C₁V₁ = C₂V₂) the tool instantly computes the unknown concentration C₂.

Raoult's Law Calculator

Enter the solute mole fraction x and the pure-solvent vapor pressure P°; by Raoult's law ΔP = x·P° the tool instantly computes the vapor-pressure lowering and the solution vapor pressure.

Calorimetry Calculator

Compute heat to change temperature Q = m c ΔT.

Enthalpy of Reaction Calculator

Enter the standard enthalpy of formation ΔH_f for each reactant and product and their stoichiometric coefficients; using ΔH° = ΣΔH_f(products) − ΣΔH_f(reactants) the tool instantly computes the standard reaction enthalpy.

Volume Percent Calculator

Enter the solute volume and the total solution volume; by v/v% = solute volume / total solution volume × 100 the tool instantly computes the volume percent concentration.

Particles to Moles Calculator

Enter the particle count N (atoms, molecules or ions); using n = N / Nₐ (Nₐ = 6.022×10²³ /mol) the tool instantly computes the amount of substance in moles.

Nernst Equation Calculator

Enter the standard potential E°, electrons transferred n and reaction quotient Q; at 25 °C the Nernst equation E = E° − (0.0592/n)·log Q instantly gives the electrode (cell) potential.

Percent Ionization Calculator

Enter the ionized concentration (e.g. equilibrium [H⁺]) and the initial concentration C₀; using % = ionized/C₀ × 100 the tool instantly computes the percent ionization of a weak acid or weak base.

Specific Gravity Calculator

Enter the substance density and the reference density (water commonly 1000 kg/m³ or 1 g/mL); by SG = ρ_substance / ρ_reference the tool instantly computes the dimensionless specific gravity.

Mass/Volume Percent Calculator

Enter the solute mass (g) and solution volume (mL); using w/v% = mass/volume × 100 the tool instantly computes the mass/volume percent concentration.

Dalton's Law of Partial Pressures Calculator

Enter a gas mole fraction xᵢ and the total pressure P_total of the gas mixture; using Dalton's law Pᵢ = xᵢ × P_total the tool instantly computes that component's partial pressure.

Graham's Law Calculator

Compute effusion rate ratio r₁/r₂ = √(M₂/M₁) of two gases.

Beer–Lambert Law Calculator

Enter the molar absorptivity ε, path length b, and concentration c to compute absorbance via the Beer–Lambert law A = ε·b·c.

RMS Velocity Calculator

Enter the absolute temperature T and molar mass M; using v_rms = √(3RT/M) the tool instantly computes the root-mean-square speed of gas molecules.

Bohr Model Energy Level Calculator

Enter the nuclear charge Z and principal quantum number n to compute the energy level of a hydrogen-like atom's electron by the Bohr model Eₙ = −13.6·Z²/n² (eV).

Radioactive Decay Calculator

Enter the initial amount N₀, elapsed time t, and half-life T½ to compute the remaining radioactive material instantly using N = N₀·(1/2)^(t/T½).

Heisenberg Uncertainty Calculator

Compute the uncertainty product Δx·Δp ≥ ħ/2.

Doppler Effect Calculator

Compute the observed frequency f' = f·(v ± v_o)/(v ∓ v_s).

Lorentz Factor Calculator

Enter a speed to compute the Lorentz factor γ = 1/√(1 − v²/c²) of special relativity.

Malus's Law Calculator

Enter the incident light intensity and the angle between polarizers to compute the transmitted intensity I = I₀·cos²θ.

Orbital Velocity Calculator

Enter central mass and orbital radius to compute the circular orbital velocity v = √(G·M/r).

Centripetal Acceleration Calculator

Compute centripetal acceleration a = v²/r = ω²r.

Free Fall Calculator

Enter fall time and gravity to compute the distance fallen and final velocity under gravity (no air resistance).

Carnot Efficiency Calculator

Compute the ideal Carnot efficiency η = 1 − T_c/T_h.

Capacitance Calculator

Compute capacitance C = Q/V from charge and voltage.

Electrical Power Calculator

Enter voltage and current to compute electrical power P = V·I instantly.

Resistivity Calculator

Find resistivity from resistance, length and area, or resistivity from temperature. Copper ρ≈1.68e-8 Ω·m; L=1 m, A=1e-6, R≈0.0168 Ω.

Thin Lens Calculator

Enter focal length f and object distance do; the thin-lens equation 1/f=1/do+1/di gives image distance di instantly. f=10 cm, do=30 cm → di=15 cm (real image).

Magnification Calculator

Enter object and image distances to compute the linear magnification m = −d_i/d_o of a lens or mirror.

Spring Constant Calculator

Enter force and extension to compute the spring constant k=F/x. F=20 N, x=0.1 m → k=200 N/m. k measures stiffness: larger k = stiffer spring.

Impulse Calculator

Enter force and time to compute impulse J = F·Δt (equal to change in momentum).

Thermal Conduction Calculator

Enter conductivity k, area A, temp difference ΔT, time t and thickness d to compute conducted heat Q=k·A·ΔT·t/d. k=0.8, A=2, ΔT=20, t=3600, d=0.1 → 1.15 MJ.

Refractive Index Calculator

Find refractive index from light speed in a medium, or from Snell's law at an interface. n=c/v. Water n≈1.333; glass≈1.5; diamond≈2.42.

Young's Modulus Calculator

Enter force, original length, cross-sectional area and extension to compute Young's modulus E=FL/(A·ΔL). F=100 N, L=1 m, A=1e-4 m², ΔL=1e-3 m → E=1e9 Pa (1 GPa).

Magnetic Force Calculator

Enter charge, velocity and magnetic field to compute the magnetic force F = q·v·B·sinθ on a moving charge.

Kinetic Friction Calculator

Compute kinetic friction F_k = μ_k·N.

Buoyancy Force Calculator

Compute buoyant force = ρ·V·g for a submerged volume.

Half-Life Calculator

Compute the remaining amount of a substance after a given time, or the elapsed time, from its half-life using N = N₀·(½)^(t/T½).

Angular Momentum Calculator

Compute angular momentum L = I·ω.

Lens Power Calculator

Compute optical power P = 1/f (in diopters) of a lens.

Moment of Inertia Calculator

Enter mass and radius to compute the moment of inertia of a solid disk or hoop about its central axis.

Rotational Kinetic Energy Calculator

Enter moment of inertia I and angular velocity ω to compute rotational kinetic energy E=½Iω². I=2 kg·m², ω=3 rad/s → E=9 J; double ω → 4× energy.

Linear Expansion Calculator

Enter the expansion coefficient, original length and temperature change to compute the change in length ΔL = α·L₀·ΔT.

Beat Frequency Calculator

Compute the beat frequency |f₁ − f₂| of two close tones.

Elastic Potential Energy Calculator

Compute spring potential energy U = ½kx².

Transformer Turns Calculator

Enter primary voltage, primary turns and secondary turns to compute secondary voltage Vs=Vp·(Ns/Np) and turns ratio Ns/Np. Vp=220 V, Np=1100, Ns=100 → Vs=20 V (step-down).

Parallel Resistance Calculator

Enter two resistances to compute their equivalent parallel resistance R = (R1·R2)/(R1 + R2).

Series Resistance Calculator

Enter three resistors R₁, R₂, R₃ and instantly get the series equivalent R = R₁ + R₂ + R₃. R₁=6 Ω, R₂=3 Ω, R₃=1 Ω → R=10 Ω.

Electric Potential Energy Calculator

Enter two charges, the distance between them and permittivity to compute their electric potential energy U = k·q1·q2/r.

LC Resonant Frequency Calculator

Enter inductance L and capacitance C to instantly compute the LC circuit resonant frequency f = 1/(2π√(LC)). L=1 mH, C=1 µF → f≈5033 Hz.

Projectile Range Calculator

Enter initial speed and launch angle to compute the horizontal range R = v₀²·sin(2θ)/g of a projectile.

Projectile Maximum Height Calculator

Enter initial speed and launch angle to compute the maximum height H = (v₀²·sin²θ)/(2·g) of a projectile.

Stopping Distance Calculator

Enter speed v and deceleration a to compute braking/stopping distance from d = v²/(2a). Doubling speed quadruples the distance.

Heat Engine Efficiency Calculator

Compute heat-engine efficiency η = W/Q_in.

Gravitational Potential Energy Calculator

Compute gravitational PE U = mgh near Earth's surface.

Electric Potential Calculator

Enter a point charge and distance to compute the electric potential V = k·q/r.

Critical Angle Calculator

Compute the critical angle θ_c = arcsin(n₂/n₁) for total internal reflection.

Banking Angle Calculator

Compute the ideal banking angle θ = arctan(v²/(rg)).

Angular Acceleration Calculator

Compute angular acceleration α = (ω₂ − ω₁)/t.

Diffraction Grating Calculator

Compute the angle of maxima d·sinθ = mλ for a grating.

Acoustic Intensity Calculator

Compute sound intensity from power and area (I = P/A).

Wavelength & Frequency Calculator

Enter wave speed and frequency (or wavelength) to find the other. λ = v/f. Speed of light 3e8 m/s, f=100 MHz → λ=3 m; audible 20 Hz–20 kHz maps to 17 mm–17 m.

Inductive Reactance Calculator

Enter frequency and inductance to compute the inductive reactance X_L = 2π·f·L.

Capacitive Reactance Calculator

Compute capacitive reactance X_C = 1/(2πfC).

Orbital Period Calculator

Enter the semi-major axis and the standard gravitational parameter to compute the orbital period via Kepler's third law T = 2π√(a³/μ).

Pressure Calculator

Enter force and area to compute pressure p = F/A.

Mechanical Power Calculator

Enter work and time, or force and velocity, to compute mechanical power.

Joule Heating Calculator

Compute Joule heating P = I²R and energy E = I²Rt.

RC Time Constant Calculator

Enter R, C, supply voltage Vs and time t to get τ=RC and the capacitor voltage Vc during charging and discharging. R=10 kΩ, C=100 µF → τ=1 s; at t=1 s a 12 V supply reaches ≈7.58 V (≈63.2%).

de Broglie Wavelength Calculator

Compute λ = h/p = h/(mv) for a particle.

Spring Natural Frequency Calculator

Enter spring constant k and mass m to compute the natural frequency f=(1/2π)√(k/m), period T=2π√(m/k) and angular frequency ω=√(k/m). k=100, m=1 → f≈1.592 Hz, T≈0.628 s.

RMS Molecular Speed Calculator

Enter absolute temperature and molar mass to compute the Maxwell-Boltzmann speeds: v_rms=√(3RT/M), v_mean=√(8RT/πM), v_p=√(2RT/M). N₂ at 273 K → vrms≈493 m/s, He ≈1300 m/s.

Magnetic Flux Calculator

Enter flux density, area and angle to compute the magnetic flux Φ = B·A·cosθ in webers (and maxwells).

Poiseuille Viscous Flow Calculator

Enter tube radius, length, pressure drop and viscosity to compute the viscous flow rate Q = π·r⁴·Δp/(8·η·L) of a Newtonian fluid.

Compton Shift Calculator

Compute scattered X-ray wavelength/energy after Compton scattering.

Wien's Displacement Law Calculator

Enter absolute temperature T to get the blackbody peak wavelength λ_max=b/T (b=2.89777e-3 m·K) and peak frequency. T=5778 K (Sun) → λ_max=502 nm (green, visible); T=300 K → 9.66 µm (IR).

Sound Intensity Level Calculator

Enter sound intensity I to get the level in decibels β=10·log₁₀(I/I₀), with I₀=10⁻¹² W/m². Whisper 1e-10 → 20 dB; conversation 1e-6 → 60 dB; rock concert 1 → 120 dB.

Cyclotron Radius Calculator

Compute the gyroradius r = mv/(qB) of a charged particle in a magnetic field.

Lorentz Force Calculator

Enter charge, velocity, magnetic and electric fields to compute the Lorentz force F = q(E + v×B).

Hall Voltage Calculator (by Carrier Charge)

Compute Hall voltage including explicit carrier charge per carrier.

Parallel Axis Theorem Calculator

Enter moment of inertia about the center of mass, mass and distance to compute the moment about a parallel axis I = I_cm + m·d².

Drift Velocity Calculator

Enter conductivity σ, carrier density n and charge q to compute the drift velocity v = μE = σE/(nq) under an applied field E.

Fermi Energy Calculator

Enter carrier density and effective mass to compute the Fermi energy, wavevector, velocity and Fermi temperature of a free-electron gas.

Time Dilation Calculator

Enter velocity and proper time to compute the dilated time via Δt=γ·Δτ, γ=1/√(1−v²/c²). v=0.8c, Δτ=1 yr → Δt=1.667 yr (you age 1 yr, Earth sees 1.67 yr).

Rydberg Formula Calculator

Enter lower n₁, upper n₂ and nuclear charge Z to get the photon wavelength, frequency, energy and spectral series. H: n₁=2, n₂=3 → 656 nm (Balmer, red).

Speed of Sound Calculator

Compute the speed of sound in an ideal gas v=√(γ·R·T/M). Air: γ=1.4, M=0.02897, T=20°C → v≈343 m/s. Also outputs km/h, ft/s and time per km.

Doppler Shift Calculator

Enter source frequency, wave speed and relative velocities to compute the observed frequency, shift and wavelength via the Doppler effect.

Volume Thermal Expansion Calculator

First-order volume expansion for solids and liquids: V=V₀(1+β·ΔT). Common β: ethanol 1.12e-3/°C, water 0.21e-3/°C, steel 35.7e-6/°C, aluminum 69e-6/°C.

Characteristic Acoustic Impedance Calculator

Compute acoustic impedance Z = ρc and reflection/transmission at a boundary.

Lens Maker's Equation Calculator

Compute focal length from refractive index and surface radii (1/f = (n−1)(1/R₁−1/R₂)).

Acoustic Intensity & Power Calculator

Compute sound intensity, intensity level and pressure level from RMS pressure.

Damped Harmonic Oscillator Calculator

Compute damping ratio, natural/damped frequency and Q of a damped oscillator.

Torsional Shear Stress Calculator

Enter torque, diameter, length and shear modulus to compute max shear stress τ_max=16T/(πd³), twist angle θ=TL/(GJ) and polar moment J=πd⁴/32. T=100 N·m, d=0.02 m → τ_max≈63.7 MPa, θ≈1.14°.

Large-Angle Pendulum Calculator

Enter length, gravity and initial angle to compute the exact large-angle period via the complete elliptic integral T=4√(L/g)·K(sin(θ₀/2)), the small-angle period and the % increase. L=1, θ₀=90° → T=18.6% longer than small-angle; θ₀=20° → +1.4%.

Acoustic Decibels & Damping Calculator

Compute decibel change and distance attenuation of sound intensity.

Bernoulli Pressure-Head Calculator

Compute pressure difference and heads from velocity/height changes (Bernoulli).

Reynolds Number Calculator

Enter density, velocity, diameter and viscosity to compute Reynolds number Re=ρvD/μ and the flow regime. Water ρ=1000, v=1, D=0.05, μ=0.001 → Re=50000 (turbulent).

Poiseuille Flow Rate Calculator

Enter tube radius, pressure difference, viscosity and length to compute the volumetric flow rate Q = π·r⁴·Δp/(8·η·L).

Stokes' Law Drag Calculator

Enter the sphere radius, velocity and fluid viscosity to compute the viscous drag from F=6πηrv, plus the terminal velocity v_t=2r²Δρg/(9η).

Capillary Rise Calculator

Enter surface tension, density, tube radius and contact angle to compute capillary rise from h=2γcosθ/(ρgr) and the Laplace pressure ΔP=2γ/r.

Conical Pendulum Calculator

Compute the period and speed of a conical pendulum from length and angle.

1D Elastic Collision Calculator

Compute final velocities of a 1D elastic collision and verify momentum/energy.

Tsiolkovsky Rocket Equation Calculator

Enter initial mass, final mass and effective exhaust velocity to compute Δv=v_e·ln(m₀/m_f), mass ratio and propellant mass. m₀=100000, m_f=10000, v_e=3000 → Δv≈6908 m/s (escape ~11200 needs bigger ratio).

Simple Harmonic Motion Calculator

Enter mass m, spring constant k and amplitude A to get angular frequency ω=√(k/m), period T=2π√(m/k), frequency, max velocity Aω, max acceleration Aω² and total energy ½kA².

Inelastic Collision Calculator

Enter masses and velocities of two objects to compute the final velocity, momentum and kinetic energy lost in a perfectly inelastic collision.

Mass-Energy Equivalence Calculator

Enter mass and speed to compute energy via E = m·c² (rest energy) or relativistic kinetic energy E = (γ−1)mc².

Inclined Plane with Friction Calculator

Enter mass, incline angle, friction coefficient and gravity to compute the acceleration, force components and whether the block slides.

Brewster Angle Calculator

Compute Brewster's angle tanθ_B = n₂/n₁ for reflected polarization.

Double-Slit Interference Calculator

Compute fringe spacing Δy = λL/d for a double-slit experiment.

Radiation Pressure Calculator

Enter the light intensity I, area A, and reflectivity r to compute the electromagnetic radiation pressure P=(1+r)I/c and the radiation force F=P·A. Fully absorbing: P=I/c; fully reflecting: P=2I/c.

Photoelectric Effect Calculator

Enter light frequency (or wavelength) and work function to compute the maximum photoelectron kinetic energy, threshold and stopping voltage.

Single-Slit Diffraction Calculator

Enter wavelength, slit width and screen distance to compute the single-slit diffraction pattern: dark fringes at a·sinθ=mλ (m=1,2,3…), central maximum width 2Lλ/a. λ=550 nm, a=0.1 mm, L=1 m → central width 11 mm.

Rayleigh Criterion Calculator

Enter wavelength and aperture diameter to compute the diffraction-limited angular resolution θ=1.22λ/D. λ=550 nm, D=3 mm (eye) → θ≈46 arcsec; D=2.4 m (Hubble) → θ≈0.057 arcsec.

Mean Free Path Calculator

Enter molecular diameter, pressure and temperature to compute the mean free path of gas molecules.

Faraday's Law of Induction Calculator

Enter turns, magnetic field, coil area and angular velocity to compute the induced EMF in a rotating coil.

Mirror Equation Calculator

Enter object distance and radius of curvature (with optional object height) to compute image distance and magnification.

Relativistic Momentum Calculator

Enter rest mass and velocity to get relativistic momentum p=γmv, Lorentz factor γ, and energies. v=0.8c → γ=1.667, momentum 1.667× the Newtonian value.

Solenoid Magnetic Field Calculator

Enter turns, length and current to compute the solenoid interior field B=μ₀nI and total flux. N=1000, L=0.1 m, I=1 A → B≈0.0126 T.

Nuclear Binding Energy Calculator

Enter proton count, neutron count and nuclear mass to compute the mass defect Δm and binding energy E_B = Δm·c².

Otto Cycle Efficiency Calculator

Enter the compression ratio and specific-heat ratio to compute the ideal Otto cycle efficiency η = 1 − 1/r^(γ−1).

Schwarzschild Radius Calculator

Enter mass m to compute the Schwarzschild radius R_s=2GM/c², escape velocity and surface gravity. Sun 1.989e30 kg → R_s≈2.95 km; Earth ≈8.87 mm.

Bragg Diffraction Calculator

Compute diffraction angle from plane spacing and wavelength (Bragg's law).

Diesel Cycle Calculator

Compute ideal Diesel cycle efficiency from compression and cutoff ratios.

Cyclotron Frequency Calculator

Compute the cyclotron frequency f = qB/(2πm) of a charged particle.

Gauss's Law Calculator

Compute electric flux Φ = Q/ε₀ and field of a spherical charge.

Larmor Frequency Calculator

Compute Larmor precession frequency f = γB/(2π).

Kirchhoff's Voltage Law Calculator

Compute currents and voltage drops in a series circuit (KVL).

Wheatstone Bridge Calculator

Enter four resistances and input voltage to compute the balanced unknown R_x=R₂R₃/R₁ and the output voltage V_out=V_in·(R_x/(R_x+R₃)−R₂/(R₁+R₂)). R₁=100,R₂=200,R₃=100,R_x=200 → balanced, V_out=0.

RLC AC Impedance Calculator

Enter resistance, inductance, capacitance and frequency to compute inductive reactance X_L=2πfL, capacitive reactance X_C=1/(2πfC), impedance Z, phase angle and resonance frequency. R=100Ω, L=0.1H, C=10μF, f=50Hz → Z≈304.5Ω.

Planck Radiation Calculator

Enter temperature to compute the total radiance and peak wavelength via the Stefan–Boltzmann law and Wien's displacement law.

Magnetic Dipole Moment Calculator

Enter turns, current and area (with field angle) to compute the magnetic dipole moment m = N·I·A, its torque and potential energy.

Electric Dipole Field Calculator

Compute axial and equatorial E-field of a dipole p = q·d.

Debye Length Calculator

Compute the Debye length λ_D of a plasma/electrolyte.

Plasma Frequency Calculator

Enter electron number density and mass to compute the plasma (Langmuir) frequency ω_p = √(n·e²/(ε₀·m_e)).

EM Wave Energy Calculator

Enter electric/magnetic field of an electromagnetic wave to compute energy densities and the Poynting vector (intensity).

Skin Depth Calculator

Enter frequency, relative permeability and conductivity to compute skin depth δ=√(2/(ω·μ·σ)). f=60 Hz, Cu (μr=1, σ=5.96e7) → δ≈8.5 mm; f=1 MHz → δ≈66 μm.

LC Resonance Calculator

Compute LC resonant frequency and characteristic impedance in multiple units.

Maxwell Speed Distribution Calculator

Enter temperature and molar mass to compute the most probable, mean and RMS molecular speeds of an ideal gas.

Eddy Current Loss Calculator

Enter lamination thickness, frequency, flux density, stack volume and core constant to compute eddy-current (iron) loss P_e = K_e·f²·B²·t²·V (W).

Thermal Resistance Calculator

Enter thickness, conductivity, area and temp difference to compute thermal resistance R=Δx/(kA), heat-flow rate Q=ΔT/R and conductance G=1/R. Copper k=401, A=1 cm², Δx=1 m → R≈24.94 K/W.

Stokes-Einstein Relation Calculator

Enter temperature, viscosity and particle radius to compute the diffusion coefficient D=kT/(6πηr) and the drag coefficient γ=6πηr. Water at 300 K, r=1 μm → D≈2.19e-13 m²/s.

Johnson-Nyquist Noise Calculator

Enter resistance, temperature and bandwidth to compute the thermal (Johnson) noise voltage, current and power.

Shot Noise Calculator

Enter DC current and bandwidth to compute shot-noise current i_n=√(2e·I·B). I=1 mA, B=1 MHz, e=1.602e-19 → i_n≈17.9 nA (RMS). It is the Poisson granularity of charge.

Seebeck Coefficient Calculator

Enter Seebeck coefficient and temperature difference to compute thermoelectric voltage V=S·ΔT. T-type 41 μV/K, ΔT=100 K → V=4.1 mV; K-type at 1000 K → 41 mV.

Equipartition Theorem Calculator

Enter degrees of freedom and temperature to compute the average energy per particle ⟨E⟩ = (f/2)·k·T and molar heat capacity.

Brownian Motion Calculator

Compute mean square displacement and RMS displacement of a Brownian particle.

Fick's First Law Calculator

Enter diffusion coefficient and concentration gradient to compute the diffusion flux J = −D·(dc/dx).

Wiedemann-Franz Law Calculator

Enter the electrical conductivity and temperature to compute the metal thermal conductivity κ=L·σ·T. Copper σ=5.96e7, T=300K → κ≈436 W/(m·K).

Drude Model Calculator

Enter carrier density and relaxation time to compute metal conductivity σ=ne²τ/m and mobility μ=eτ/m. Copper n=8.5e28, τ=2.5e-14 → σ≈5.99e7 S/m.

Quantum Hall Resistance Calculator

Enter the Landau level filling factor to compute the quantized Hall resistance R_H = R_K/ν, where R_K = h/e².

Biot–Savart Law Calculator

Compute the magnetic field from currents (straight wire and loop).

Carnot Cycle Calculator

Compute Carnot efficiency and heat-pump/refrigerator COP.

Fresnel Equations Calculator

Compute reflectance and transmittance at a flat interface (normal incidence).

Compton Scattering Calculator

Compute the Compton wavelength shift Δλ = λ_c(1−cosθ).

Poynting Vector Calculator

Enter electric field amplitude to compute the average/peak intensity, magnetic field amplitude and total energy density of an EM wave.

Adiabatic Process Calculator

Compute volume/pressure relation and work for an adiabatic gas process.

Entropy Change Calculator

Enter moles, heat capacity, temperatures and volume ratio to compute the entropy change of an ideal gas ΔS = n·Cv·ln(T2/T1) + n·R·ln(V2/V1).

Venturi Flow Rate Calculator

Enter upstream area, throat area, pressure difference and density to compute Venturi-tube flow rate Q=A₂√(2ΔP/(ρ(1−(A₂/A₁)²))). A₁=0.01, A₂=0.001, ΔP=5000 Pa, ρ=1000 → Q≈0.00318 m³/s, v₂≈3.18 m/s.

Bulk Modulus Calculator

Compute bulk modulus K = −V·Δp/ΔV and compressibility.

Power Factor Calculator

Convert real power, voltage and current to power factor PF.

Shear Modulus Calculator

Enter shear force F, area A, shear distance L and lateral displacement Δx to compute shear modulus G=F·L/(A·Δx). F=1000 N, A=1e-4 m², L=1 m, Δx=1.26e-4 m → G≈79.4 GPa (close to steel).

Poisson's Ratio Calculator

Enter axial and lateral strain to compute Poisson's ratio ν = −ε_lateral/ε_axial, plus shear modulus and Young's modulus.

Newton's Law of Cooling Calculator

Enter initial temperature, environment temperature, cooling constant and time to compute the temperature T(t)=T_env+(T₀-T_env)·e^(-kt).

Heat Transfer Coefficient Calculator

Compute heat transfer Q = h·A·ΔT and thermal resistance.

Thermal Stress Calculator

Enter Young's modulus E, expansion coefficient α and temperature change ΔT to compute thermal stress σ=E·α·ΔT. E=200 GPa, α=12e-6/K, ΔT=50 K → σ=120 MPa, ΔL=6e-4 m.

Magnetic Permeability Calculator

Enter magnetic flux density B and field strength H to compute permeability μ = B/H, relative permeability and susceptibility.

Relative Permittivity Calculator

Enter capacitance, plate area and spacing to compute relative permittivity εr=C·d/(ε₀·A), absolute ε and C/C₀. Vacuum C=8.854e-11 F → εr=1; water-filled C=7.08e-9 F → εr≈80.

Work Function Calculator

Enter photon wavelength λ and maximum photoelectron kinetic energy KE to compute work function φ=hc/λ−KE and threshold frequency ν0=φ/h. Na λ=400nm, KE=0.82eV → φ≈2.28eV, λ₀≈544nm; W λ=200nm, KE=1.7eV → φ≈4.5eV.

Hall Coefficient Calculator

Compute the Hall coefficient R_H = V·t/(I·B) and carrier density.

Thermionic Emission Calculator

Enter cathode temperature T and work function W to compute emission current density J=A·T²·exp(-W/kT). Tungsten W=4.5 eV, T=2500 K → J≈6369 A/m²; Richardson A=1.2×10⁶ A/(m²·K²).

Inductor Energy Calculator

Enter inductance and current to compute the magnetic energy stored in an inductor E = ½·L·I².

LC Resonance Frequency Calculator

Compute the LC resonant frequency f = 1/(2π√LC).

RL Time Constant Calculator

Enter inductance and resistance to compute the RL time constant τ=L/R. L=0.1 H, R=100 Ω → τ=1 ms.

Transformer Ratio Calculator

Enter primary/secondary turns (Np, Ns), primary voltage and current to compute turns ratio n=Np/Ns, voltage ratio, current ratio, Vs and Is. Np=1000, Ns=100, Vp=100, Ip=1 → Vs=10 V, Is=10 A (step-down).

Ampere Force Calculator

Compute the magnetic force on a current-carrying wire (F = ILB·sinθ).

Self-Inductance Calculator

Enter coil turns, flux per turn and current to compute self-inductance L=N·Φ/I. N=100, Φ=0.0001 Wb, I=0.5 A → L≈0.02 H.

Mutual Inductance Calculator

Enter the linked flux and primary current (or both self-inductances) to compute mutual inductance between two coils.

Magnetic Torque Calculator

Enter turns, current, area and field (with angle) to compute the torque τ = N·I·A·B·sinθ on a current loop in a magnetic field.

Back EMF Calculator

Compute the back electromotive force of an inductor (ε = −L·di/dt).

Terminal Voltage Calculator

Enter EMF, current, internal resistance and charge/discharge mode to compute terminal voltage V=ε∓Ir, voltage drop Ir and internal power loss P=I²r. ε=12 V, I=2 A, r=0.5 Ω → discharge V=11 V, charge V=13 V.

Relativistic Velocity Addition Calculator

Enter observer speed v, object speed u' and light speed c to compute u=(v+u')/(1+vu'/c²). v=0.5c, u'=0.5c → u≈0.8c (not 1.0c); v=c, u'=c → u=c (light-speed limit).

Relativistic Energy Calculator

Enter mass m and velocity v to compute total energy E=γmc², rest energy E0=mc² and kinetic energy K=(γ−1)mc². v=0.9c, m=1 kg → E≈2.29×10¹⁷ J, K≈1.94×10¹⁷ J.

Capacitor Combination Calculator

Enter up to 3 capacitors and the connection mode to compute the equivalent capacitance. Series 1μF+1μF → 0.5μF; parallel 1μF+2μF+3μF → 6μF.

Magnetic Field of a Straight Wire Calculator

Enter current I and distance r to compute the magnetic field B=μ₀I/(2πr). I=10 A, r=0.05 m → B≈4.0×10⁻⁵ T (≈0.4 G).

Q Factor (Quality Factor) Calculator

Enter up to 3 frequencies (f0, f1, f2) to compute the quality factor Q=f0/(f2−f1). Q=100, f0=1 kHz, BW=10 Hz; higher Q means narrower bandwidth and lower loss.

Physical Pendulum Calculator

Enter moment of inertia, mass, gravity and pivot distance to compute the period of a physical (rigid-body) pendulum.

Torsion Pendulum Calculator

Enter moment of inertia I and torsion constant κ to compute period T=2π√(I/κ), frequency f and angular frequency ω. I=1 kg·m², κ=1 → T≈6.283 s; watch hairspring I=1e-7, κ=1e-5 → T≈0.628 s (1.59 Hz).

Standing Wave Calculator

Enter wave speed, length and harmonic number to compute standing-wave frequencies f_n=nv/(2L) and wavelengths λ_n=2L/n. v=340, L=1 → f₁=170 Hz, f₂=340 Hz; guitar v=5000, L=0.65 → f₁≈3846 Hz.

Thin-Film Interference Calculator

Enter refractive index, wavelength and order to compute constructive thickness t=mλ/(2n) and destructive t=(m+½)λ/(2n). n=1.5, λ=500 nm, m=1 → t_c≈166.7 nm; anti-reflective MgF₂ t≈100 nm.

Carbon Dating Calculator

Compute the age of a sample from its remaining ¹⁴C fraction.

Coulomb Potential Energy Calculator

Compute electrostatic potential energy U = kq₁q₂/r.

Stefan-Boltzmann Law Calculator

Enter emissivity, surface area and temperature to compute blackbody radiated power. Human body ε=0.97, A=1.5 m², T=310 K → P≈744 W.

Reverberation Time Calculator

Enter room volume and total absorption to compute reverberation time RT60=0.161·V/A. V=100 m³, A=10 m² Sabine → T=1.61 s. Concert halls target 1.8–2.2 s, speech 0.8–1.2 s.

Sound Pressure Level Calculator

Enter RMS sound pressure to compute SPL=20·log₁₀(p/p₀) in dB, sound intensity I=p²/(ρc) and SIL=10·log₁₀(I/I₀). p=0.02 Pa (talk) → 60 dB; p=1 Pa → 94 dB; p=200 Pa (jet) → 140 dB (pain).

Electric Current Density Calculator

Compute current density J = I/A, drift velocity and resistance per length.

Magnetic Dipole Field Calculator

Enter magnetic moment and distance to compute the on-axis and equatorial magnetic field of a dipole B = (μ₀/4π)·m/r³.

Photon Momentum Calculator

Enter frequency or wavelength to compute the photon momentum p = h/λ = E/c (and the equivalent mass).

Mechanical Wave Energy Calculator

Enter medium density, angular frequency, amplitude, wave speed and volume to compute wave energy density E=½ρω²A², intensity I=E·v and total energy. ρ=1.2, ω=1, A=1, v=340 → E=0.6 J/m³, I=204 W/m².

Compton Wavelength Calculator

Compute the Compton wavelength λ_c = h/(mc) of a particle.

Center of Mass Calculator

Compute the center of mass of a two-body system.

Brayton Cycle Calculator

Compute ideal Brayton (gas-turbine) cycle thermal efficiency.

Internal Energy Calculator

Enter degrees of freedom, moles and temperature to compute the internal energy of an ideal gas U = (f/2)·n·R·T.

Mass Defect Calculator

Enter proton count, neutron count and actual nuclear mass to compute the mass defect, binding energy and binding energy per nucleon.

Hubble's Law Calculator

Enter distance or recession velocity to compute the other via v = H₀·d, plus redshift and light-travel time.

Gyroscopic Precession Calculator

Compute precession rate Ω = τ/(Lω) of a spinning top.

Orbital Energy Calculator

Enter the primary mass and orbit radius to compute specific orbital energy, velocity, period and escape velocity.

Carnot Refrigerator Calculator

Compute COP of an ideal Carnot refrigerator/heat pump.

Stellar Luminosity Calculator

Enter the stellar radius and surface temperature to compute luminosity L=4πR²σT⁴, the solar-luminosity ratio and the absolute bolometric magnitude. Sun R=6.957e8 m, T=5778 K → L≈3.84e26 W.

Coriolis Effect Calculator

Compute the Coriolis acceleration a = 2vΩsinφ.

Virial Theorem Calculator