Daily Interest Calculator
Work out how much interest a balance earns or costs each day, and the total for any number of days. Choose simple or daily compounding and a 365 or 360-day year to match how your bank or lender counts interest.
The nominal yearly rate (APR), not the daily rate.
Used to show the end date and dates in the table.
How to use the Daily Interest Calculator
- Enter the principal: the savings balance, loan balance or invoice amount.
- Enter the annual interest rate in percent and the number of days.
- Pick the day-count basis (365 for most savings and consumer loans, 360 for many commercial loans) and the method.
- Read the interest per day, the total for the period and the ending balance.
- Check the schedule and the comparison table, and download them as CSV if you need them.
Daily interest formulas
Daily rate = annual rate ÷ days in year (365, 360 or 366 depending on the convention).
- Simple daily interest: Interest = P × (r ÷ B) × days. The amount is the same every day.
- Compounded daily: Balance = P × (1 + r ÷ B)days, and interest = balance − P. Each day's interest is added to the balance.
P is the principal, r the annual rate as a decimal and B the day-count basis. Example: $10,000 at 5% for 30 days on a 365-day basis gives simple interest of 10,000 × 0.05 ÷ 365 × 30 = $41.10, or $41.18 compounded daily.
Interest per day on $10,000
| Annual rate | Per day (365 basis) | Per day (360 basis) | 30 days (365, simple) |
|---|---|---|---|
| 1% | $0.27 | $0.28 | $8.22 |
| 2% | $0.55 | $0.56 | $16.44 |
| 3% | $0.82 | $0.83 | $24.66 |
| 4% | $1.10 | $1.11 | $32.88 |
| 5% | $1.37 | $1.39 | $41.10 |
| 6% | $1.64 | $1.67 | $49.32 |
| 8% | $2.19 | $2.22 | $65.75 |
| 10% | $2.74 | $2.78 | $82.19 |
| 20% | $5.48 | $5.56 | $164.38 |
| 25% | $6.85 | $6.94 | $205.48 |
Which day-count basis should I use?
- Actual/365: most savings accounts, CDs, credit cards and consumer loans in the US and UK.
- Actual/360: many commercial and business loans, money-market instruments and some adjustable-rate mortgages.
- 366: some lenders divide by 366 in leap years; check your loan agreement.
Credit cards usually compound daily using a daily periodic rate (APR ÷ 365), while many personal loans and late-payment interest charges use simple interest. Your statement or contract states the exact method.
Frequently asked questions
How do you calculate daily interest?
Divide the annual rate by the number of days in the year to get the daily rate, then multiply by the balance. For example, $10,000 at 5% on a 365-day basis earns 10,000 × 0.05 ÷ 365 = $1.37 per day. Multiply by the number of days for simple interest over a period.
What is the difference between simple daily interest and daily compounding?
With simple daily interest the daily amount is always calculated on the original principal. With daily compounding each day's interest is added to the balance, so the next day's interest is slightly larger. Over a few days the difference is tiny; over years it becomes noticeable.
Why do some lenders use a 360-day year?
The 360-day convention (often called Actual/360 or the banker's year) dates back to easier manual calculation. Dividing the annual rate by 360 instead of 365 makes the daily rate about 1.4% higher, so a borrower pays slightly more interest over a full year. It is common on commercial loans and some mortgages.
What is per diem interest?
Per diem simply means per day. In mortgages and auto loans it is the interest that accrues each day on the balance, used for example to calculate the interest due at closing or the exact payoff amount on a given date.
How much interest does $100,000 earn per day?
At 5% on a 365-day basis, $100,000 earns about $13.70 per day (100,000 × 0.05 ÷ 365). At 4% it is about $10.96 per day, and at 2% about $5.48 per day.
What is the APY for daily compounding?
APY = (1 + r ÷ 365)^365 − 1. A 5% rate compounded daily gives an APY of about 5.127%, slightly higher than the 5% nominal rate because interest earns interest.
Are my numbers saved or sent anywhere?
No. The calculation runs in your browser and nothing is uploaded. Your last inputs are only remembered locally on your device for convenience.