Financial tools

Compound Interest Calculator

Calculate the future value of an initial investment with optional monthly contributions. Set a monthly interest rate and term in months, then add more scenarios to compare total contributions, interest earned, and estimated balance.

Set up an investment scenario

Enter the interest rate per month and choose a term in months. Interest compounds monthly, and monthly contributions are added at each month’s end. Results are temporary and clear when you refresh this page.

Compare your scenarios

Each calculation appears here so you can compare the assumptions and estimated totals side by side.

Scenario Starting amount Monthly deposit Monthly rate Period Total invested Interest earned Future value
Your calculations will appear here. Add another scenario to compare its result.

How compound interest grows an investment

Compound interest calculates growth on both the original investment and interest already earned. Regular monthly contributions can also build over time. This calculator lets you compare scenarios with different starting amounts, contributions, rates, and durations.

Formula and calculation method

The monthly rate is converted to a decimal by dividing it by 100. The initial investment grows for the selected number of months, and each monthly contribution is treated as a deposit made at the end of its month. The estimated future value is the sum of those amounts.

What this estimate includes

Results assume a constant monthly rate compounded monthly. They do not account for taxes, fees, inflation, or changing rates. Use the same currency when comparing amounts; no currency conversion is performed. This estimate is for planning and is not a guaranteed return.