Compound Interest Calculator

See how a starting balance and monthly contributions can grow with monthly compounding.

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If I start withaddmonthly, earn% foryears, what will I have?

Assumes monthly compounding and contributions made at the end of each month. Returns are estimates, not guarantees.

Ending balance
Monthly compounding
Total contributed
Interest / growth
Months
Effective annual rate

How compound interest grows money

Compounding earns returns on the starting balance and on growth accumulated in earlier periods. Recurring contributions add new principal throughout the timeline.

Monthly contributionsThis calculator assumes each monthly contribution is added at the end of the month, then participates in subsequent compounding periods.

Rate, time and contributions

Longer time periods can magnify the effect of compounding. Increasing recurring contributions often has an equally important effect because it increases the amount of money participating in future growth.

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Common questions

Are contributions added at the start or end of the month?

They are modeled at the end of each month. Beginning-of-month contributions would produce a slightly higher ending balance.

Does this predict investment returns?

No. It shows a mathematical scenario using the annual rate you enter. Real investment returns vary over time.

What happens if the interest rate is zero?

The ending balance is simply the starting balance plus all monthly contributions.