Calculate simple interest and total amount with any principal, rate, and time period. Supports yearly, monthly, and daily time units. Pure client-side, instant results.
This simple interest calculator helps you quickly calculate the interest earned or paid on a principal amount over a specific time period. Simple interest is calculated only on the original principal amount, making it ideal for short-term loans, savings accounts, and basic investment calculations. All calculations happen in your browser — your financial data never leaves your device.
Simple interest is a method of calculating interest where the interest is computed only on the original principal amount. The formula is: Interest = Principal × Rate × Time. Unlike compound interest, simple interest does not earn interest on previously accumulated interest.
The simple interest formula is I = P × r × t, where I is the interest amount, P is the principal (initial amount), r is the annual interest rate as a decimal, and t is the time in years. The total amount is A = P + I = P(1 + rt).
Simple interest is commonly used for short-term loans, auto loans, some mortgages, savings accounts with no compounding, and certificates of deposit (CDs). It is also used in legal calculations and certain types of bonds.
With simple interest, you only earn/pay interest on the original principal. With compound interest, you earn/pay interest on both the principal and any previously accumulated interest. Over long periods, compound interest yields significantly higher returns (or costs) than simple interest.