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Compound interest calculator

See how savings grow with compound interest and regular contributions.

Runs 100% in your browser
Future value
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You contributed
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Interest earned
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How to calculate compound interest

  1. Enter your starting amount. Type your initial principal and any monthly contribution.
  2. Set rate, years and frequency. Add the annual rate, how many years, and the compounding frequency.
  3. Read the breakdown. See the future value split into what you put in versus interest earned.

The power of compounding

Small, regular contributions plus time beat large one-off deposits made late — the longer money compounds, the more of your balance is interest rather than contributions. Use the savings calculator for goal-based planning, and the inflation calculator to see what your future balance is worth in today’s money.

Educational tool only — not financial advice. Assumes a constant rate and excludes taxes and fees. Real returns vary.

Frequently asked questions

What is compound interest?
Compound interest is interest earned on both your original money and the interest it has already earned. Over time the growth accelerates, which is why starting early matters so much.
How is it calculated?
Future value = principal × (1 + r/n)^(n·t), plus the future value of any regular contributions. Here r is the annual rate, n the times it compounds per year, and t the number of years. This tool does it for you and splits the result into contributions vs interest.
Does compounding frequency matter?
Yes — more frequent compounding (daily or monthly vs annually) earns a little more for the same rate. You can change the frequency below.
Does this include tax or inflation?
No. It shows nominal growth. To see what the result is worth in today’s money, use the inflation calculator.
Is my data sent anywhere?
No — the calculation runs entirely in your browser.

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