Compound Interest Calculator
Watch your money grow, contributions plus compounding returns.
Your numbers
Breakdown
Balance growth over time
How this calculator works
Compound interest is interest earning interest, and it is the single most powerful force in long-term investing. Each period, your balance grows by the return rate, and the next period's growth is calculated on that larger balance. Add regular contributions and the effect becomes dramatic: over 20–30 years, investment growth can dwarf everything you actually put in. This compound interest calculator models exactly that, letting you set an initial amount, a monthly contribution, an assumed annual return and the compounding frequency.
Play with the two levers that matter most: time and contributions. Starting ten years earlier usually beats earning a higher return, because compounding needs time to do its heavy lifting, the growth curve stays flat for years, then bends sharply upward. Monthly contributions matter even more than most people expect; they are the fuel the compounding engine burns. The frequency setting (monthly vs daily) changes results only slightly, banks love advertising daily compounding, but the return rate and your savings habit decide 99% of the outcome. Treat the rate as a long-term average, not a promise: markets fluctuate, and this calculator shows the smooth mathematical path, not the bumpy real one.