FINANCIAL CALCULATORS
Simple Interest Calculator
Calculate simple interest on a principal over time.
100% free
No sign-up
Private — runs in your browser
Instant results
KEY TAKEAWAYS
- Calculate simple interest on a principal over time.
- Free to use — no sign-up, no account and no usage limits.
- Runs entirely in your browser, so the numbers you enter stay private.
- Works on desktop and mobile with instant, accurate results.
Last updated: June 2026
About the Simple Interest Calculator
Simple interest is charged only on the original principal: I = P × r × t. Enter the three values to get the interest and total.
Frequently asked questions
How is simple interest different from compound?
Simple interest never earns interest on previously-earned interest, so it grows in a straight line rather than a curve.
Free online tool from ConvertFleet. Calculations run entirely in your browser — nothing you type is sent anywhere. Results are estimates for general guidance only.