See how your savings could grow over time with compound interest. Enter a starting amount, a monthly contribution, an expected annual return, and the number of years. The calculator shows your estimated final balance, how much of it comes from your own contributions, and how much comes from growth.
Compound Interest Calculator
| Year | Contributed | Growth | Balance |
|---|
Assumes monthly compounding, contributions at the end of each month, and a constant return. Real returns vary from year to year and can be negative. Taxes and fees are not included.
How to Read the Results
- Total contributed is the money you put in yourself: the starting amount plus all monthly contributions.
- Growth earned is the estimated return on that money, including returns earned on previous returns – the compounding effect.
- In the table, the gray part of each bar is your contributions and the amber part is growth. Over long periods, growth often becomes the larger share.
The Formula Behind the Calculator
Each month, the balance grows by the monthly rate (the annual return divided by 12), and then the monthly contribution is added. Repeating this for every month produces the final balance. It is equivalent to the standard future-value formulas for a lump sum plus a series of regular payments.
Tips for Using This Calculator
- Try several return assumptions. Compare a cautious scenario (for example 4%) with a more optimistic one (for example 8%). No return is guaranteed.
- Think in today’s money. To estimate purchasing power, subtract expected inflation from the return – for example, use 4% instead of 7% if you expect about 3% inflation. See how inflation erodes savings.
- Remember costs. Fund fees and taxes reduce real-world returns. Lowering costs is one of the few things you control – see index funds vs. actively managed funds.
- Test the power of time. Change only the number of years and watch how much the growth figure changes.
Learn More
- The Power of Compound Interest (With Examples)
- Dollar-Cost Averaging vs. Lump Sum Investing
- More free tools
This calculator is for general educational purposes only. Results are estimates based on the numbers you enter and simplified assumptions; they are not financial, investment, or tax advice. See our Disclaimer.