Free tool · Personal Finance
Compound interest calculator
Shows how a starting amount plus a regular monthly deposit grows over the years when interest is added monthly and itself earns interest.
General education, not financial advice. Your situation may differ. Disclaimer.
Everything is calculated in your browser. Nothing you type is sent to us or anyone else, and nothing is stored.
How it works
Each month the balance earns one twelfth of the yearly rate, then the deposit is added at the end of the month.
Because interest is earned on earlier interest, growth speeds up over time, which is why starting early matters more than the amount.
Each month: balance = balance × (1 + rate ÷ 12) + deposit
Worked example
Starting with 1,000 and adding 200 a month at 6% a year, after 10 years you would have 34,595.27, of which 25,000 is what you paid in and 9,595.27 is growth.
Limits
- Real returns vary from year to year and investments can fall in value. A fixed rate is an illustration, not a forecast.
- Tax, fees and inflation are not included.
Questions
What rate should I use?
For a savings account, use its stated interest rate. For investments, a cautious long-run figure is safer than recent returns, and remember the value can go down.
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