Compound Interest Calculator
See how your money grows over time with compounding and optional monthly contributions.
Enter your numbers and select Calculate to see results.
About This Calculator
This compound interest calculator projects the future value of an initial deposit, optionally combined with regular monthly contributions, at a given annual interest rate and compounding frequency. It breaks down how much of the final balance came from your contributions versus interest earned.
How This Is Calculated
A = P (1 + r/n)^(nt)
- A
- — Future value
- P
- — Initial principal
- r
- — Annual interest rate (decimal)
- n
- — Compounding periods per year
- t
- — Time in years
$10,000 at 7% annual interest, compounded monthly for 20 years with no contributions grows to about $40,387.
Assumptions
- Assumes a fixed annual rate of return for the entire period — real markets fluctuate.
- Monthly contributions are converted to the selected compounding frequency for calculation purposes.
- Does not account for taxes, fees, or inflation.
Frequently Asked Questions
Related Calculators
Investment Calculator
Project how your investments could grow over time with regular contributions.
Savings Calculator
See how much your savings could grow with regular deposits and interest.
Future Value Calculator
Calculate what a lump sum today will be worth in the future.
Simple Interest Calculator
Calculate interest earned without compounding — a fixed percentage of the original principal.
Retirement Calculator
Project how much you'll have saved by your target retirement age.
Last updated January 15, 2026. Results are estimates for informational purposes only — read our disclaimer.