Compound Interest Calculator
Future value is your balance compounded monthly at the annual rate divided by 12, with each month's deposit added.
Worked example
| Principal amount | $10,000 |
|---|---|
| Annual interest rate | 7% |
| Number of months | 120 |
| Monthly contribution | $200 |
| Future Value | $54,714 |
| Total Contributions | $34,000 |
| Total Interest Earned | $20,714 |
How it is calculated
Each month the calculator adds interest of (annual rate / 100 / 12) x the current balance, then adds the monthly contribution. It repeats this for every month of the term.
Total contributions = principal + monthly contribution x months. Total interest earned = the sum of the monthly interest amounts.
Assumptions and limits
- Assumes one constant annual rate; real returns vary and can be negative.
- Taxes, fees and inflation are not deducted, so the result is a nominal estimate.
Educational estimate only; not financial, tax, legal or investment advice.
FAQ
How do I calculate compound interest with monthly deposits?
Compound the balance monthly at the annual rate divided by 12 and add each deposit. With $10,000 at 7% for 120 months plus $200 a month, the future value is $54,714.
What is the difference between contributions and interest earned?
Contributions are the money you put in ($34,000 in the example). Interest earned is the growth on top ($20,714).
Does this calculator include taxes or fees?
No. It shows a nominal projection at a constant rate; fees, taxes and inflation are not deducted.