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Compound Interest Calculator

See how savings or an investment can grow when interest is added back to the balance. Choose how often interest compounds and add an optional monthly deposit.

Final balance–
Total deposited–
Interest earned–

Year-by-year growth

YearTotal depositedInterest earnedBalance

For general information only. Results are estimates based on the numbers you enter and are not financial advice. Actual figures from a bank or lender may differ because of fees, rounding or payment timing.

How to use the Compound Interest Calculator

  1. Enter your starting amount, yearly rate and number of years.
  2. Pick how often interest compounds and add a monthly deposit if you plan to contribute regularly.
  3. Read the final balance and the yearly table.

How it is calculated

Without deposits, A = P × (1 + r ÷ n)n × t, where r is the annual rate, n is the number of compounding periods per year and t is the number of years. With a monthly deposit, deposits are assumed to be made at the end of each month and earn interest at the equivalent monthly rate.

Worked example

10,000 at 5% compounded monthly for 10 years grows to about 16,470.09, so the interest earned is 6,470.09. Adding 100 a month for the same period lifts the final balance to about 31,998.32 from 22,000.00 deposited.

Why time matters

The longer money stays invested, the more interest is earned on previous interest. Starting early, even with small deposits, usually makes a bigger difference than a slightly higher rate. A higher compounding frequency helps a little, but the rate and the time have much more effect.

Limits of this estimate

It assumes a constant rate and no taxes, fees or inflation. Real returns, especially from investments, vary and are not guaranteed.

Frequently asked questions

What is compound interest?

Interest calculated on the original amount plus the interest already added, so the balance grows faster over time.

What is the difference between monthly and daily compounding?

Daily compounding adds interest more often, which gives a slightly higher balance. The difference is usually small compared with the effect of the rate and the years.

Are monthly deposits made at the start or end of the month?

This calculator assumes the end of each month.

Is the result guaranteed?

No. It is a mathematical estimate for a fixed rate. Real savings and investment returns can change and may be lower or higher.

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Last updated: November 6, 2026