Compound interest calculator
Enter your starting amount, regular deposits and interest rate.
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- Total deposited
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- Interest earned
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- Interest share
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Year-by-year table
| Year | Deposits | Interest | Balance |
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This calculator gives estimates for general information only and isn't financial advice. Check figures with your lender, accountant or tax office before making decisions.
How compound interest works
Compound interest means you earn interest on your interest. Each period, interest is added to your balance, and the next period's interest is calculated on that bigger balance. Over long stretches the effect snowballs: the interest earned in later years can dwarf what you put in.
The calculator adds your monthly deposit at the end of each month and applies interest at the compounding frequency you choose. More frequent compounding earns slightly more, but the interest rate and the number of years matter far more.
The rule of 72
For a quick estimate, divide 72 by the annual interest rate to find roughly how many years it takes money to double. At 6% that's about 12 years; at 8% about 9 years.
Want the full explanation? Read our guide: Compound interest explained, with real examples.
Questions people ask
What is the compound interest formula?
For a single deposit, the future value is A = P(1 + r/n)^(nt), where P is the starting amount, r the annual rate, n the number of compounding periods per year and t the number of years. Regular deposits are added on top, which this calculator handles for you.
How much will $10,000 grow in 10 years?
At 5% compounded monthly with no further deposits, $10,000 grows to about $16,470. Adding $200 a month takes it to roughly $47,500.
Does compounding frequency matter much?
A little. At 5%, monthly compounding earns about 1% more over 10 years than yearly compounding. The rate and time invested have a much bigger effect.
Does this include tax or inflation?
No. Interest is usually taxable and inflation reduces what money can buy, so real growth will be lower than shown.