Simple Interest Calculator
Calculate simple interest and total amount in seconds.
What is Simple Interest?
Simple interest is calculated only on the original principal amount, for the entire time period, without compounding — unlike compound interest, where earlier interest itself starts earning interest. The formula is Interest = Principal × Rate × Time ÷ 100, where the rate is an annual percentage and time is in years.
How to use it
- Enter the principal amount, the annual interest rate, and the length of time in years (decimals like 1.5 for eighteen months are fine).
- The interest earned and total amount (principal plus interest) update instantly.
Simple interest is commonly used for short-term loans, certain types of bonds, and some basic savings calculations where the interest is paid out rather than reinvested. Because it grows in a straight line rather than accelerating over time, it is easier to predict than compound interest, but it also produces a smaller return over long periods for the same rate. If you want to see how the same numbers behave with compounding instead, try the Compound Interest Calculator elsewhere on this site.