Compound Interest Calculator
How your savings grow over time
Saving or investing? Enter a starting balance, monthly contribution, expected return and time horizon to see how compounding grows your money.
The power of compounding
Compound interest means you earn returns on your past returns, not just your contributions. The two biggest levers are time and rate — small differences in either produce huge differences decades out. Try adding ten years and watch the "interest earned" line.
Frequently asked questions
How does compound interest work?
Each period's earnings are added to your balance, so future earnings are calculated on a larger amount — growth accelerates over time.
What return should I assume?
Historically the broad US stock market has averaged roughly 7% per year after inflation, but returns vary and aren't guaranteed.