Money & Finance · Free tool
Compound Interest Calculator
See how much your money grows with compound interest. Add starting balance, monthly contributions, and watch the curve.
Updated April 2026
Final balance
$134,270
You contributed
$61,000
Interest earned
$73,270
What it does
A compound interest calculator that shows what a starting balance plus regular monthly contributions becomes over time at a given return rate. The number at 30 years is often shocking — this is the magic of compounding.
$200/month at 7% for 30 years = $245,000. At 40 years = $525,000. Time is the dominant variable, not amount. Starting early beats contributing more. Pair with our investing guide.
How to use it
- Enter starting balance and monthly contribution.
- Set expected annual return (7% is a common long-term stock market assumption).
- Set number of years to invest.
- See the ending balance and total contributed vs. interest earned.