Compound Interest Calculator
See how an amount grows when interest earns interest. Add a monthly contribution, choose the compounding frequency and get the future value with a year-by-year breakdown.
Runs in your browser
How to use
- Enter the starting amount and annual interest rate.
- Choose the duration and compounding frequency.
- Add a monthly contribution if you save regularly.
- Read the future value and interest earned.
How it works
Without deposits the formula is A = P × (1 + r/n)^(n·t), where P is the initial amount, r the annual rate, n the number of compounding periods per year and t the number of years. With monthly deposits, each deposit is added at the end of the month and then grows at the same rate.
More frequent compounding gives slightly more interest: 5% compounded monthly equals an effective annual rate of 5.12%.
Examples
- Lump sum
- 10,000 at 5% compounded monthly for 10 years → 16,470.09.
- With savings
- Same plus 200 a month → 47,526.55, of which 13,526.55 is interest.
Common uses
- Savings and deposit accounts
- Planning long-term goals
- Comparing compounding frequencies
Privacy & security
This tool runs entirely in your browser. Your files and text are never uploaded to our servers — processing happens on your device and results are created locally. How each tool handles files
Frequently asked questions
What's the difference between APR and APY?
APR is the nominal yearly rate; APY (or effective rate) includes compounding. At 5% monthly compounding the APY is 5.12%.
Are taxes and fees included?
No. Interest income is often taxed, which reduces the real growth.
Last updated: