Simple Interest Calculator
Work out interest that is charged only on the original amount, with no compounding.
| Interest | $1,500.00 |
|---|---|
| Total (principal + interest) | $11,500.00 |
| Time in years | 3 |
How to use it
- Enter the starting amount and the yearly rate.
- Enter the time and its unit. Days are counted on a 365-day year.
Formula
I = P × r × tP = principal, r = annual rate as a decimal, t = time in yearsTotal = P + I
Example
$10,000 at 5% simple interest for 3 years earns 10,000 × 0.05 × 3 = $1,500.00, for a total of $11,500.00. For 90 days it earns 10,000 × 0.05 × 90 ÷ 365 = $123.29.
Questions
Simple vs compound interest?
Simple interest is paid only on the principal. Compound interest is also paid on interest already earned, so it grows faster. See the compound interest calculator.
Where is simple interest used?
Some car loans, short-term personal loans, bonds' coupon payments and many textbook problems. Credit cards and savings accounts compound.
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Last reviewed 2026-10-11. Found a mistake? Tell us.