Investment Calculator

Shows what a starting amount and a monthly contribution can grow to when the annual return is compounded every month.

1. Enter the amount already invested and the amount you add at the end of each month.
2. Enter the annual return and the number of years.
3. Read the future value, the amount you put in, and the growth.

Monthly compound growth with end-of-month deposits

The annual rate is divided by 12. Future value = starting amount × (1 + monthly rate)^months + monthly deposit × [((1 + monthly rate)^months − 1) / monthly rate]. Deposits are added at the end of the month. Years are rounded to the nearest month, and the result is rounded to the cent.

Source. The annual rate is divided by 12. The starting amount compounds for every month. Each deposit is added at the end of the month and compounds only after that. Years are rounded to the nearest month, and the future value is rounded to the cent. Investor.gov publishes a compound-interest calculator for the same family of formulas. Investor.gov compound interest calculator.

Updated November 1, 2026

Starting with $10,000.00 and adding $200.00 at the end of each month, at 7% compounded monthly for 10 years, grows to $54,713.58. You put in $34,000.00.

• A return of 0% simply adds the deposits to the starting amount.
• Fees, taxes, and inflation are not included.
• The rate is an assumption you type. It is not a forecast.

How is this different from the compound interest page?

This page always compounds monthly and always treats contributions as end-of-month deposits. The compound interest page lets you choose a compounding frequency for the starting balance.

What if I contribute nothing?

Leave the monthly contribution at 0. The future value is then only the starting amount, compounded monthly.