Compound Interest Calculator

Calculate compound interest and investment growth with our free online calculator. See how your money grows over time with different interest rates and compounding frequencies.

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The compound interest calculator helps you understand how investments grow over time through the power of compounding. Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods—essentially 'interest on interest.' This calculator lets you see how different factors like interest rate, compounding frequency, time period, and regular contributions affect investment growth. It's an essential tool for retirement planning, savings goals, and understanding the long-term impact of financial decisions. All calculations are performed locally in your browser.
  1. Enter your initial investment (principal) amount
  2. Enter the annual interest rate (percentage)
  3. Select the compounding frequency
  4. Enter the investment period (years)
  5. Optionally add monthly contribution amount
  6. Click 'Calculate' to see results
  7. View final amount, total interest, and year-by-year breakdown

What is compound interest?

Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest (calculated only on principal), compound interest allows your money to grow exponentially over time because you earn 'interest on interest.'

How does compounding frequency affect returns?

More frequent compounding leads to higher returns. For example, monthly compounding produces more returns than annual compounding at the same interest rate, because interest is calculated and added to the principal more often, making subsequent interest calculations based on a larger amount.

What is the Rule of 72?

The Rule of 72 is a quick way to estimate how long it takes for an investment to double. Simply divide 72 by the annual interest rate. For example, at 6% interest, your money doubles in approximately 72/6 = 12 years.

Why are regular contributions important?

Regular contributions significantly accelerate wealth accumulation through dollar-cost averaging and increased compounding effects. Even small regular contributions can grow substantially over time due to compound interest, making consistent investing one of the most powerful wealth-building strategies.