Compound Interest Calculator
Enter an initial amount, annual interest rate, period, monthly contribution, and compounding frequency to estimate final balance, total contributions, and interest earned.
Runs locally in your browser. This tool does not upload your input.
Inputs
Results
- Final balance
- 20,514.24
- Total contributions
- 13,000.00
- Interest earned
- 7,514.24
- Monthly contribution
- 100.00
Estimate how an initial amount and monthly contributions grow over time.
How to calculate compound interest
Estimate how an initial amount and recurring monthly contributions can grow with compound interest over a chosen period.
How to use it
- Enter the initial amount you already have.
- Add the annual interest rate and the number of years.
- Enter the monthly contribution and choose how often interest compounds.
- Review final balance, total contributions, and interest earned.
What the result assumes
The calculator treats the annual rate as a nominal rate and converts it to an effective monthly growth rate based on the compounding frequency. Monthly contributions are added at the end of each month.
Comparing scenarios
- Raise the monthly contribution to see the effect of saving more.
- Try different periods to see how time changes the final balance.
- Compare rates carefully; small differences compound over long periods.
Local calculation
The numbers are calculated in your browser and are not sent to a server.
Compound interest calculator FAQ
- Is this financial advice?
- No. It is a planning estimate only. Real investments can include taxes, fees, risk, and changing rates.
- When are monthly contributions added?
- The tool adds each monthly contribution after that month's interest, which is a conservative end-of-month assumption.
- Can the interest rate be zero?
- Yes. With a zero rate, the result is the initial amount plus the monthly contributions.