What is compound interest?
Compound interest is interest earned on both your original money and the interest it has already earned. Over time this snowball effect can grow savings far faster than simple interest — which is why starting early matters so much.
How this calculator works
It compounds monthly and assumes your contributions are added each month. Each month, your balance earns one-twelfth of the annual rate, then your contribution is added, and the cycle repeats for the number of years you choose.
- Starting amount — what you have today.
- Monthly contribution — what you add each month.
- Annual rate — your expected average yearly return.
The power of time
The biggest driver of compound growth isn't the amount you start with — it's how long you stay invested. Even small, consistent contributions can become significant over decades because the interest keeps compounding on a growing balance.
Note: this is an estimate for education only. Real returns vary year to year and are not guaranteed. It does not account for tax or inflation.