Investment Growth Calculator
See how compounding and steady contributions could grow your money over time — free, no sign-up, plain-English.
Assumes monthly compounding at a constant rate. Real returns vary year to year and are never guaranteed — try a few rates to see the range.
How compound growth works
Compounding is when your returns start earning returns of their own. Early on it looks slow; given enough time it snowballs, which is why starting and staying consistent matter more than picking a perfect moment. The green portion of each bar above is growth on top of what you put in.
Two levers do most of the work: the monthly contribution (consistency) and time. Learn the ideas behind this in what compound interest is and dollar-cost averaging, and if you're just getting started, how to invest for beginners.
Frequently asked
How does a compound interest calculator work?
It projects how an investment could grow when returns are reinvested and earn returns of their own. You enter a starting amount, an optional monthly contribution, an assumed annual return and a time horizon; the tool compounds it month by month to estimate a future value. It's a hypothetical model, not a prediction.
What is a realistic annual return to use?
There's no guaranteed number, and past performance never guarantees future results. For context, a broad stock index has historically averaged in the high single digits per year over long periods, but any single year can be sharply up or down. Try a few different rates to see how sensitive the outcome is.
Why does the monthly contribution matter so much?
Because regular contributing plus compounding is what does the heavy lifting over time — often more than the starting amount. Investing a fixed sum on a schedule is the idea behind dollar-cost averaging.
Is this financial advice?
No. This calculator is an educational tool that models hypothetical growth from the numbers you enter. It is not advice, not a recommendation, and not a promise of any return. Investments can lose money.
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