Free tools

Compound Interest Calculator

Calculate compound interest and see how your investment grows over time — free online compound interest calculator.

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Results

Final balance
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Total interest
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Total contributed
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Year Balance Interest earned Total deposited

Compound Interest Calculator

Enter your initial amount, interest rate, time period, compounding frequency, and optional monthly contributions to see your final balance and a year-by-year breakdown. Results update instantly as you type.

What is compound interest?

Compound interest means you earn interest on both your principal and the interest already accumulated. Over time this creates exponential growth — often called "the eighth wonder of the world." The more frequently interest compounds (daily vs. annually), the faster the balance grows.

The compound interest formula

A = P(1 + r/n)nt where P is the principal, r is the annual rate (as a decimal), n is compounding periods per year, and t is time in years.

Common uses

  • Projecting the future value of savings accounts, ISAs, or investment portfolios
  • Comparing savings accounts with different compounding frequencies
  • Understanding the long-term effect of regular monthly contributions
  • Calculating how much debt grows if left unpaid

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