Money & Finance
Compound interest calculator
Enter an amount, a rate and a time. See what it grows to with compound interest, how much of that is interest, and how long it takes to double.
- Free, no sign-up
- Runs in your browser
- Nothing uploaded
Amount
Only changes the symbol and number format. No exchange rates are used.
Type of interest
Time in
Extras (optional)
A regular saving added at the end of each month.
Shows the result in today's money.
Result
Year-by-year growth
How it works
Compound interest is interest on the amount and on the interest already earned. Simple interest is only on the original amount.
Compound: A = P × (1 + r ÷ n)n × t
Simple: A = P × (1 + r × t)
P = starting amount, r = annual rate, n = compounding periods per year, t = years
Monthly additions are added at the end of each month and grow at the rate equivalent to your chosen compounding. The effective annual rate is (1 + r ÷ n)n − 1. The rule of 72 estimates the years to double as 72 ÷ the rate.
Frequently asked questions
What is the difference between compound and simple interest?
Simple interest is the same amount every year. Compound interest grows faster because each period's interest is added to the amount that earns interest next.
Does more frequent compounding matter?
Slightly. At 8% a year for 5 years on 100,000, yearly compounding gives 146,933 and daily compounding gives 149,176.
Is anything sent anywhere?
No. It all runs in your browser.