Compound Interest Calculator

Future value with monthly contributions

How compound interest is calculated

Each monthly contribution is added at the start of the month, and interest accrues on the balance at annual rate ÷ 12 per month. With monthly compounding that interest is added to the balance every month; with annual compounding it is added once every 12 months.

Example

Start with 10,000, add 500 a month for 20 years at 7% compounded monthly. You contribute 130,000 in total and end with about 302,370, so roughly 172,370 is interest.

Frequently asked questions

What is the Rule of 72?

Divide 72 by the annual return in percent to estimate how many years it takes to double your money. At 6% a year, that is about 12 years.

Monthly vs. annual compounding: what is the difference?

The more often interest is added to the balance, the faster it grows. 5% compounded monthly is the same as about 5.12% compounded once a year (the APY).

Are taxes and fees included?

No. Results are before tax, fees and inflation. Real returns also vary from year to year, so use the result as a planning estimate.

Related calculators