Compound interest calculator
See how your savings or investments could grow over time with regular contributions and compound interest.
Final balance
- Total contributed
- Total interest
Estimates only, for illustration.
Year by year
| Year | Contributed | Interest | Balance |
|---|---|---|---|
How this calculator works
Enter a starting amount, how much you'll add each month, an expected yearly return and the number of years. The calculator compounds monthly: each month it adds your contribution and a month's growth, then repeats.
The results split your final balance into what you put in and what your money earned. Over long periods, the earnings often end up larger than the contributions.
Keep in mind
- Returns aren't guaranteed. Savings accounts pay a known rate, but investments rise and fall. Try a lower rate to see a cautious result.
- Inflation reduces what your money will buy in the future. Using a return after inflation (for example 5% instead of 7%) shows the result in today's dollars.
- Fees and taxes reduce growth. Low-cost index funds and tax-advantaged accounts like 401(k)s and IRAs help you keep more.
Common questions
Compound interest is interest earned on your interest. Each month, what you've earned is added to your balance, so the next month's interest is worked out on a bigger amount. Over many years, this makes growth speed up.
For a savings account, use its APY. For long-term investments in stock funds, many people use 5 to 7% a year as a cautious estimate after inflation. Investment returns vary a lot from year to year and aren't guaranteed.
Money invested earlier has more years to compound. Someone who starts in their twenties can end up with far more than someone who saves the same amount each month but starts ten years later.