Interest Calculator
Simple and compound interest on any amount. Change the numbers and the result updates instantly.
How it works
Simple interest is calculated only on the amount you start with. Compound interest is calculated on the amount plus interest already earned, so it grows faster. The more often interest compounds and the longer the time, the bigger the gap.
Example
Example: $10,000 at 5% for 10 years earns $5,000 in simple interest. With monthly compounding it earns about $6,470 before any deposits.
Tips
- Change one input at a time to see what moves the result most.
- Use realistic rates. Check current averages before you decide.
- Results are estimates and do not replace advice from a licensed professional.
Frequently asked questions
Is this calculator free?
Yes. There is no sign-up and nothing is stored on our servers; the math runs in your browser.
How accurate is it?
It uses standard formulas, but real offers include fees, rate changes and taxes that can differ. Treat the result as an estimate.
Sources and method
Page last updated November 2026. See our editorial policy and disclaimer.