Simple Interest Calculator 💰
Calculate simple interest on a principal amount. Enter the principal, annual interest rate, and time in years — all in your browser, instant results.
About the Simple Interest Calculator
This simple interest calculator runs entirely in your browser. Enter the principal, annual interest rate, and number of years to calculate the interest earned and the total amount. Nothing is uploaded to a server — all calculations happen instantly with JavaScript on your device.
How the calculation works
The calculator uses the standard simple interest formula:
I = P × r × t and A = P + I
Where P is the principal, r is the annual interest rate (as a decimal, e.g. 5% becomes 0.05), and t is the time in years. I is the interest earned and A is the total amount (principal plus interest). Unlike compound interest, simple interest is calculated only on the original principal.
Frequently asked questions
Does this tool upload my data? No. All calculations happen locally in your browser. Your inputs never leave your device.
What is the difference between simple and compound interest? Simple interest is calculated only on the principal, while compound interest is calculated on the principal plus accumulated interest. Over time, compound interest grows faster.
Can I use months instead of years? Convert months to years by dividing by 12. For example, 18 months = 1.5 years.
Can I use a different currency? Yes. The numbers are unit-agnostic — enter values in any currency and the result will be in the same currency.