Free calculator
Compound Interest Calculator
See how a starting amount plus regular monthly contributions can grow over time, and how much of the final total is interest.
You put in
$25,000
Interest earned
$31,131
Final balance
$56,131
How your balance grows
This calculator assumes a fixed annual return compounded monthly, with contributions added each month. Real investment returns vary year to year and are not guaranteed. This is general education, not financial advice.
How compound interest works
Compound interest means you earn returns not just on your original money, but on the returns it has already earned. Over time, this snowball effect becomes the main driver of long-term growth, which is why starting early matters so much.
How to use this calculator
Enter your starting amount, how much you plan to add each month, an estimated annual return rate, and how many years you will let it grow. The calculator shows how much you contributed, how much you earned in interest, and your final balance.
A commonly used long-term return estimate for a diversified stock portfolio is somewhere around 7 percent a year after inflation, though real returns vary a great deal from year to year and are never guaranteed. Try a few different rates to see the range of possible outcomes.
This calculator is for general education only and is not financial advice. Investment returns are not guaranteed, and the value of investments can fall as well as rise.
The Wealth Theory Newsletter
Money tips worth reading
Join thousands of readers getting practical finance advice every week. No spam, unsubscribe anytime.