Simple interest is calculated only on the original principal amount during the whole period. This means interest is not added to the balance to generate new interest. For example, if you lend $1,000 at 10% per year for 2 years with simple interest, the interest is always calculated on the same $1,000.

Fill in the initial amount, interest rate and time. Then choose whether the time is in months or years and click "Calculate simple interest". The tool will show the total interest and final amount including interest. You can adjust the values as many times as you like to simulate different scenarios.

The calculation follows the classic simple interest formula: I = P × r × t, where I is the interest, P is the principal, r is the interest rate per period in decimal form (for example, 5% = 0.05) and t is the time in years. If you choose the time in months, the calculator converts it to years by dividing the number of months by 12. The final amount is obtained by adding the interest to the principal: Final amount = P + I.