Free Compound Interest Calculator — watch your money grow.
Enter four numbers and instantly see what compounding does to your money — final balance, total growth and a live year-by-year chart. Everything runs right here in your browser; nothing is saved or sent anywhere.
Compound Interest Calculator
Compound interest means your returns earn returns of their own. Fill in your starting amount, monthly contribution, expected return and time period — every figure and the chart below recalculate as you type. Amounts are shown without a currency symbol, so it works in any currency.
What you invest today
What you add every month
Long-term average, before inflation
How long you let it compound (1–60)
Final balance
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What you end up with
Total contributed
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Starting amount + all monthly deposits
Total growth
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Interest earned on top of your deposits
Simplified model: fixed annual return, monthly compounding, contributions added at the start of each month, no inflation or taxes. Not financial advice.
The math behind the calculator.
Compound interest
Your money earns a return, and next period that return earns a return too. Over one or two decades this snowball effect is what makes the curve bend upward — most of the growth happens in the later years.
Monthly compounding
Your expected annual return is converted to an equivalent monthly rate. Each month, your contribution is added first and the whole balance then grows by that rate — month after month, for the full time period.
Real data, live chart
The chart isn’t decoration: it’s drawn from the actual balance at the end of every year of the simulation, and it redraws instantly whenever you change an input.
Embed this calculator on your own site.
Free to use anywhere — your readers get the live calculator, right on your page. No account, no cost.
Embed code
Paste this into any page that allows iframes (WordPress, Squarespace, a custom HTML block). It includes a small “Powered by Yieldly” credit that links back to yieldly.nl.
Good to know before you calculate.
How does the calculator handle monthly contributions and compounding?
Your expected annual return is converted to an equivalent monthly rate. Each month your contribution is added first, then the whole balance grows by that monthly rate — repeated for your full time period.
Does it account for inflation or taxes?
No — it's a simplified model with a fixed annual return, no inflation adjustment and no taxes, so you can see the pure mechanics of compounding.
Can I embed this calculator on my own site?
Yes — scroll down to the “Embed this calculator” section above for a ready-to-paste code snippet.