Interest Calculator – Simple Interest and Total Amount
Use this free interest calculator to compute simple interest on a principal amount. Enter the principal, annual interest rate and time in years. The tool shows total interest earned and the final amount (principal + interest). Works for loans and deposits where interest does not compound.
Interest Calculator
Calculate simple interest on a principal amount. Enter the principal, annual rate and time in years to get total interest and final amount.
How the simple interest formula works
Simple interest is calculated as:
I = P × r × t
- I = interest amount
- P = principal (initial amount)
- r = annual interest rate as a decimal (e.g. 0.05 for 5%)
- t = time in years
Total amount = principal + interest. Unlike compound interest, simple interest does not add interest back to the principal, so the same amount of interest is earned each period.
When to use simple interest
Simple interest is commonly used for short-term loans, some personal loans and certain fixed deposits. If your loan or deposit agreement specifies simple interest, this calculator gives you the exact interest and total amount. For products that compound (e.g. most savings accounts, mutual funds), use the compound interest calculator instead.
All calculations run in your browser. No data is stored or sent to any server. You can try different principal amounts, rates and time periods to compare scenarios.