Simple Interest Calculator
Calculate simple interest in seconds with our free simple interest calculator. Enter principal, rate and time to see interest earned and total amount.
About this tool
Simple interest is the most basic way interest is calculated: you earn (or pay) a fixed percentage of the original amount for each year. No compounding, no surprises. Our free simple interest calculator does the math for you instantly.
Just enter the principal amount, the annual interest rate, and the number of years. The tool shows both the interest earned and the total amount you will have at the end.
How to use
Type the starting amount (principal) into the first field. This is the money you invest or borrow. Next, enter the annual interest rate as a percentage - for example, type 5 for 5 percent.
Finally, enter the time period in years and press Calculate Interest. The result appears immediately below the button. Try different rates and time periods to compare scenarios side by side.
The math behind it
The math behind simple interest is straightforward: Interest = Principal x Rate x Time / 100. The total amount is the principal plus the interest.
For example, $10,000 at 5 percent for 3 years earns $10,000 x 5 x 3 / 100 = $1,500 in interest, for a total of $11,500. Banks rarely pay simple interest on savings - they use compound interest - but loans between friends and some short-term deals still use it.