Compound Interest Calculator

See how your money grows over time with compounding. Factor in initial deposit, monthly contributions, interest rate, and time horizon.

See how your money grows over time with compounding. Factor in initial deposit, monthly contributions, interest rate, and time horizon.

What you can figure out

• How a lump-sum deposit grows over a long time horizon at a given annual return.
• The additional upside from consistent monthly contributions on top of the initial balance.
• Why starting earlier beats contributing more — the time variable dominates the math.
• Side-by-side comparison of savings-account APYs vs. market-return assumptions.

How it works

The compound-interest calculator takes an initial deposit, a monthly contribution, an annual rate, and a number of years, then applies standard time-value-of-money math to show the ending balance. Returns compound monthly by default to match how most high-yield savings accounts pay interest. Adjust the rate to model different scenarios — a 4% high-yield savings rate, a 7% long-term stock-market average, or anything in between.

Privacy

This calculator runs entirely in your browser. Nothing you type is saved, transmitted, or shared with us or any third party. See our privacy policy for the full details, or browse more tools on the calculators page.