What is compound interest?

Compound interest means you earn interest on your interest, not just on the original principal. Over time this creates exponential growth — Albert Einstein reportedly called it the eighth wonder of the world.

How often should interest compound?

More frequent compounding means slightly more growth. Daily compounding earns marginally more than monthly, which earns more than annually. For most savings accounts, the difference between daily and monthly compounding is very small.

What is the Rule of 72?

Divide 72 by the annual interest rate to estimate how many years it takes to double your money. At 6% annual interest: 72 ÷ 6 = 12 years to double.

How are monthly contributions factored in?

Each monthly contribution is added to the principal before interest is applied. This is called a future value of an annuity — regular contributions dramatically accelerate growth.

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Compound Interest Calculator

Calculate compound interest growth with monthly contributions — see your investment grow over time with a chart.

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About this tool

Calculate how your investment or savings grow with compound interest. Enter principal, annual interest rate, compounding frequency, and optional monthly contributions. See total value, total interest earned, and a year-by-year growth breakdown.

How to use

1 Enter your starting amount (principal).
2 Set the annual interest rate and compounding frequency.
3 Optionally add monthly contributions.
4 Set the investment period in years to see the total result and year-by-year breakdown.

Frequently Asked Questions

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