Compound Interest Calculator

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 in your browser. Like every page on the site, it also runs analytics and session-recording tools that can record what appears on screen. See our privacy policy for the full details, or browse more tools on the calculators page.