Compound Interest Calculator
See how money grows when interest earns interest.
How to use this calculator
- Enter a starting amount, the annual interest rate in percent, and the number of years.
- Pick how often interest is added: yearly, or monthly as most savings accounts do.
- Optionally add a regular contribution; it is paid in once per compounding period, so monthly compounding means a monthly deposit.
- The result splits into what you paid in and what the interest added on top. This is a model, not financial advice: real products have fees and taxes.
Frequently asked questions
- What is compound interest?
- Interest that is added to the balance so that it earns interest itself. 1,000 at 5% becomes 1,050 after one year, and the next year's 5% is calculated on 1,050, not 1,000.
- Does monthly compounding earn more than yearly?
- Slightly, at the same nominal rate: 5% compounded monthly works out to about 5.12% per year, because each month's interest starts earning immediately.
- How dramatic is the effect over long periods?
- Very. At 7% per year, money roughly doubles every 10 years: 10,000 becomes about 20,000 in 10 years and about 76,000 in 30 years, without any extra deposits.
- Are taxes and fees included?
- No. The calculator shows pure compounding; real accounts and funds charge fees and returns are usually taxed. Treat the result as an upper bound, not a promise.