Interest Per Day Calculator
Enter a loan or deposit balance and the annual rate to compute the daily rate and daily interest accrued.
Input Data
Results
At a glance:The Interest Per Day calculator converts an annual rate into daily interest, for the daily cost of a loan or daily interest earned on a deposit. Simple interest: daily rate = annual rate ÷ 365; daily interest = balance × daily rate. Used for bridging loans, overdue interest, daily-accruing loans or high-yield deposit income. It uses simple interest (no compounding); if interest rolls over, actual is higher; some institutions use 360 or 366 days, per contract.
Formula
Daily rate = annual rate ÷ 365.
Daily interest = balance × daily rate (daily rate as decimal).
$$\text{DailyRate} = \dfrac{\text{AnnualRate}}{365}$$$$\text{InterestPerDay} = \text{Balance} \times \dfrac{\text{AnnualRate}}{365}$$How to Use
- Enter the loan or deposit principal balance.
- Enter the annual rate.
- View the converted daily rate and daily interest.
Daily rate and daily interest at various balances and annual rates (365-day base)
| Balance | Annual rate | Daily rate | Daily interest |
|---|---|---|---|
| HK$1,000,000 | 4% | 0.010959% | HK$109.59 |
| HK$500,000 | 4% | 0.010959% | HK$54.79 |
| HK$250,000 | 6% | 0.016438% | HK$41.10 |
Daily rate = annual rate ÷ 365; daily interest = balance × daily rate. Simple interest (no compounding). A 360-day base gives a slightly higher daily rate; compounding raises the actual amount. Per contract.
Case Studies
Case 1: Daily accrued interest cost on a loan
Mr Chan has a HK$1,000,000 bridging loan at 4% and wants the daily interest cost.
Daily rate = 4% ÷ 365 ≈ 0.010959%; daily interest = 1,000,000 × 0.010959% ≈ HK$109.59.
Each day delayed costs about HK$109.59 more; repaying 10 days early saves about HK$1,096 — meaningful for bridging/short-term financing: pay a day earlier, save a day's interest.
Case 2: Overdue interest and the 360-day base difference
May owes HK$500,000 overdue at 4%, accruing daily: daily interest = 500,000 × (4% ÷ 365) ≈ HK$54.79. Over 30 days that is about HK$1,644.
But note the base difference: a 360-day base (common in some loans) gives daily rate = 4% ÷ 360 ≈ 0.011111%, daily interest ≈ HK$55.56, slightly higher; 30 days ≈ HK$1,667, about HK$23 more than the 365 base.
Practical notes: (1) simple interest — no roll-over of accrued interest; compound contracts cost more; (2) base 365/360/366 varies by institution and product; (3) actual overdue/penalty terms per the loan contract. Pair with the simple-interest and compound-interest calculators.
FAQ
Is this simple or compound interest?
This calculator uses simple interest — daily interest is on the principal only, not rolling accrued interest into principal. If interest rolls over, the actual amount is higher; use a compound calculator instead.
Why do some institutions use 360 days?
The accrual base varies by institution and product — commonly 365, 360 or leap-year 366. The base changes the daily rate and interest slightly; actual is per contract.
What is daily interest for?
It is used to estimate the cost of bridging loans, overdue interest, daily-accruing loans, or the daily interest income of high-yield deposits.
365 or 360 days — how different?
Both bases are common and the choice affects the amount. 365-day (Actual/365) uses the real calendar (365, or 366 leap); daily rate = annual ÷ 365 — the default here. 360-day (30/360 or Actual/360) treats a year as 360 days, common in some commercial loans, interbank rates, bonds; daily rate = annual ÷ 360. The same annual rate divided by 360 gives a slightly higher daily rate (smaller denominator), so 360-base daily interest is slightly higher. At 4%, HK$500,000: 365-base ≈ HK$54.79/day; 360-base ≈ HK$55.56/day, about HK$0.77 more per day. Small per day, but over large balances or long periods (e.g. HK$1m for a full year) the gap grows — a 360 base collects about 1.39% more over a year (365/360 ≈ 1.0139), a hidden cost for borrowers, extra gain for depositors. Advice: (1) when borrowing, check the base — 360 means slightly higher real cost; (2) for deposits, 360 helps you (higher daily), but retail deposits mostly use 365; (3) compare products by converting to effective annual rate (EAR); (4) leap years add one day's interest under Actual/365 or 366. Actual terms per contract; this tool gives the 365-base estimate.
When is daily interest most useful, and can it save interest?
Converting an annual rate to daily interest is very practical — it shows 'time is money': repaying a day earlier or delaying a withdrawal by a day maps directly to a concrete interest amount. Uses: (1) bridging loan cost — often daily-interest, short term; knowing the daily figure shows the value of selling the old property and repaying early. (2) Overdue/penalty interest — credit cards and loans accrue daily; the daily figure makes the cost of delay tangible, pushing you to clear fast (card rates often exceed 30%). (3) Daily-accruing loans/overdrafts — the longer you use, the more interest. (4) High-yield deposit daily income. How to save: repay a day earlier, save a day's interest — if no prepayment penalty, repay high-rate daily-interest debt early (even by days); schedule repayment right after payday; clear credit cards within the grace period to avoid compounding daily interest; quantify the cost of delay (e.g. '30 days late costs HK$X') for rational decisions. Caveats: simple-interest estimate here; compound contracts cost more; check prepayment penalties; actual base per contract. Pair with the compound-interest and monthly-repayment calculators.
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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.