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Compound interest calculator

See how your savings grow with compound interest and regular monthly contributions, and how much of the final balance is interest.

Your savings

Add contributions at the

Final balance

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Starting amount
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Total contributions
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Total interest
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  • Money you put in –
  • Total interest –

Year-by-year growth

Contributions, interest and balance each year
YearContributionsInterestBalance

What you type stays on this device. Nothing is uploaded.

How to calculate compound interest

  1. Enter your starting amount, how much you’ll add each month, the yearly interest rate and the number of years.
  2. Choose how often interest is compounded, and whether you add money at the start or end of each month.
  3. Read your final balance and how much of it is interest, then check the year-by-year table.

Questions

Are my numbers sent anywhere?

No. The calculator works in your browser on this device. Your numbers are never uploaded or stored, and they’re gone when you close the page.

What is compound interest?

Interest that earns interest. Each time interest is added to your balance, the next interest is worked out on the bigger balance, so growth speeds up over time. $10,000 at 5% a year becomes $16,289 after 10 years, compared with $15,000 with simple interest.

How are compounding and monthly contributions combined?

Your starting amount grows by the standard formula P × (1 + r/n)^(n × t), where n is how many times a year interest is compounded. Each month’s contribution grows at the same pace from the day it’s added, at the start or end of the month.

Is the result guaranteed?

No. It’s an estimate, not financial advice. It assumes the same rate every year, with no fees, taxes or withdrawals. Savings accounts change their rates, and investment returns go up and down.