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).
Input Data
Results
At a glance:Burn rate measures how much net cash a pre-break-even company consumes each month and how long the cash lasts — the core survival metric for startups. net burned = beginning - ending cash; monthly burn = net burned / months; runway = ending cash / monthly burn. Example: start 500k, after 3 months 350k left → burned 150k, 50k/month; runway = 350k / 50k = 7 months. A shorter runway means raise revenue, cut cost or arrange funding. WARNING: Assumes constant burn and all ending cash usable; update monthly. This is net burn (revenue netted); gross spend is separate.
Formula
Burn rate = (cash at start − cash at end) / number of periods.
Runway (months) = current cash / monthly burn rate.
$$\text{Monthly Burn} = \dfrac{C_{\text{begin}} - C_{\text{end}}}{n}$$$$\text{Runway} = \dfrac{C_{\text{end}}}{\text{Monthly Burn}}$$How to Use
- Enter the cash at the start and end of the period.
- Enter the elapsed months.
- View the monthly burn and the runway in months.
FAQ
Is burn rate gross or net spend?
This tool uses net burn — beginning minus ending cash already nets off revenue, reflecting the true net cash consumption. For gross spend only, add revenue back to ending cash, or divide total expenses by months.
Why use ending cash for the runway?
Because ending cash is what you actually have left to burn. Divide it by the monthly burn to get roughly how many months you survive at the current pace. A runway under 6 months is usually a warning — cut spend or raise funds.
What if ending cash is higher than beginning?
Then you added cash net (reached positive cash flow); net burn is negative and the tool shows runway 0 (not burning). Then the focus shifts from survival to using the surplus — build reserves, reinvest or repay early debt.
What is the difference between gross and net burn?
Gross burn = total monthly operating expenses (payroll, rent, marketing, cloud) ignoring revenue — how much it costs to keep the lights on. Net burn = gross burn minus revenue — the actual monthly cash drop. This tool derives net burn from the cash change. Net burn links directly to runway; gross burn helps assess cost structure and worst-case (revenue = 0) survival.
How do I extend a short runway?
Three levers, often combined: (1) Cut costs — freeze non-core hiring, renegotiate rent/supplier contracts, trim weak marketing; lowers the denominator, lengthens runway. (2) Raise revenue — faster monetisation, higher pricing, deposits. (3) Fundraise — equity, loans or government SME schemes add cash. Start fundraising ~6 months before cash runs out; emergency funding is harder and cheaper when you have time.
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References
Content review: Calculatorism Finance Team. Results are for reference only; please refer to the relevant authorities for the official figures.