Simple Interest Calculator

How this calculation works

Simple interest is principal multiplied by annual rate and time.

Using the result

Enter values that belong to the same period and use consistent units. For monetary inputs, use the same currency throughout. The calculator updates in your browser and does not require registration.

Worked example

Start with simple round numbers to check the relationship between the inputs and result. Then replace them with your real figures. This helps you see whether the output changes in the direction you expect.

What this calculator does not include

Simple calculators intentionally isolate one formula. Real business outcomes can also depend on taxes, fees, returns, timing, attribution methods, accounting treatment and other assumptions. Use the result as an analytical aid rather than a guarantee.