Find out how much your money will grow thanks to compound interest. Enter an initial deposit, monthly deposit, rate, and number of years — the result appears instantly.
Compound interest means that the interest your money earns is added to the principal, and in the next period that interest earns interest too. In other words — interest earns more interest. That's why an investment you let grow for long enough doesn't grow in a straight line, but accelerates.
Albert Einstein supposedly called compound interest the "eighth wonder of the world". Whether he really said it or not, the point holds: it is one of the most powerful effects you can use in personal finance — and the sooner you start, the bigger the difference it makes.
For a single lump-sum deposit, the final value is given by the formula:
With regular monthly deposits, the future value of each individual deposit is added on top, each one earning interest from the day you make it. The calculator above does this math for you.
It depends on what you invest in. A savings account today offers low single-digit percentages, while a broad stock index (ETF) has historically averaged 7–10 % per year before inflation. For a realistic long-term estimate when investing in stocks, 7 % is often used.
This calculator shows the pure effect of compound interest without fees or inflation, so the principle is as clear as possible. If you want to include inflation, entry fees, or ongoing costs, use our detailed investment calculator.
Because compound interest grows exponentially. The final years of investing add the most, because you are earning interest on already-large capital. Try setting the same deposit for 20 and then for 30 years in the calculator — the difference will probably surprise you.
