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Compound Interest Calculator

See how time and compounding can multiply your savings exponentially

Initial Deposit ($)

Monthly Contribution ($)

Annual Return (%)

Years to Grow

Compounding Frequency

Future Account Balance

With re-invested earnings

Total Interest

Total Contributions

Yield on Cost

Compounding Journey

About the Compound Interest Calculator

Compound interest means you earn interest on your interest, which is why long-term savings can grow much faster than the money you put in. See how an initial deposit and regular contributions could grow over time.

How to use the Compound Interest Calculator

Enter your Initial Deposit ($) and any Monthly Contribution ($).
Enter the Annual Return (%) and the Years to Grow.
Choose the Compounding Frequency: Monthly, Quarterly or Annually.
Press Visualize Growth to see the final balance and a growth chart. Use Copy Result or Reset as needed.

Formula and method

A = P × (1 + r ÷ n)^(n × t)

P is the starting amount, r the annual rate, n the number of compounding periods per year and t the number of years. Regular contributions add the future value of an annuity on top.

Worked example

$10,000 growing at 7% a year, compounded annually for 10 years: 10,000 × 1.07¹⁰ = $19,671.51. The money nearly doubles without any new deposits.

The value of a higher rate. $10,000 left for 10 years grows to about $19,672 at 7% compounded yearly, but only about $13,439 at 3%. The same money, with the same time, ends up roughly $6,200 apart. The Rule of 72 gives a quick check: at 7%, money doubles in about 72 ÷ 7 ≈ 10.3 years.

When to use the Compound Interest Calculator

Seeing how a savings account, deposit or investment could grow over 5, 10 or 30 years.
Comparing what happens when interest is added monthly instead of yearly.
Showing the effect of starting early versus waiting a few years to begin saving.
Understanding how quickly credit card or loan interest can build up when it compounds.

Common mistakes to avoid

Confusing the nominal rate with the effective rate. With monthly compounding, a stated 12% actually earns slightly more than 12% a year.
Assuming the return is guaranteed. Investment returns change from year to year, so treat the result as an illustration.
Ignoring inflation, fees and taxes, which all reduce your real growth.

Tips

Start early: time matters more than the size of each deposit.
More frequent compounding helps only slightly. The rate and the time have the biggest effect.
Returns on investments are not guaranteed and vary from year to year.

Frequently Asked Questions

What is the Rule of 72?

Divide 72 by the annual return to estimate how many years it takes to double your money. At 8 percent, money doubles in about 9 years.

Is compound interest better than simple interest?

For savings, yes, because interest itself earns interest. For loans it works against you.

What is the Rule of 72?

A quick mental shortcut. Divide 72 by the annual interest rate to estimate the years needed to double your money. It is most accurate for rates between about 6% and 10%.

How is compound interest different from simple interest?

Simple interest is only paid on the original amount. Compound interest is paid on the original amount and on the interest already earned, so growth speeds up over time.

Compound Interest Calculator