Simple Interest Calculator
Work out the interest on a lump sum when interest is paid only on the original amount.
Quick answer: enter your details below and click Calculate — your result appears instantly, right here in your browser. Nothing you enter is uploaded or stored.
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Calculators
Enter your details below.
How to use
- Enter the original amount, the annual interest rate and the time in years.
- Press Calculate to see the interest and the total amount.
- Change any value to compare different rates or time periods.
About this tool
This calculator finds simple interest using the formula interest = principal times rate times time, divided by 100. The rate is the annual percentage rate and time is measured in years. Unlike compound interest, the interest here never earns further interest, so the amount grows by the same amount each year.
Frequently asked questions
When is simple interest used?
It is commonly used for short-term loans and some savings products where interest is calculated only on the original amount, not on interest already earned.
How is the total amount calculated?
The total amount is the original amount plus the interest. For example, 10,000 at 5% for 3 years earns 1,500 in interest, giving a total of 11,500.