How to calculate simple interest
- Type the principal amount and the yearly rate.
- Type the time in years and extra months.
- Read the interest, the total and the yearly table.
About this tool
Simple interest is charged only on the original amount, so it grows by the same sum every year. Enter the principal, the yearly rate and the time in years and months. You get the interest, the total, and a table that shows the running total at the end of each year, with the formula written out.
Common questions
What is the simple interest formula?
Interest = P x R x T / 100, where P is the principal, R the yearly rate in percent and T the time in years.
How is simple interest different from compound interest?
Simple interest is always worked out on the starting amount. Compound interest is worked out on the starting amount plus interest already earned.
Can I enter months?
Yes. Use the extra months box. Six months is treated as 0.5 years.
Is it free to use?
Yes. There's no sign-up, and you can use it as often as you like.
Is my text uploaded anywhere?
No. This tool runs inside your browser, so what you enter stays on your device.
Do I need to install anything?
No. It works in your browser on a computer or a phone.