Compound Interest Calculator
Visualize how your money can grow exponentially over time.
Total Future Value
Compound Interest Calculator — Watch Money Grow
Compound interest means you earn returns on your returns — and over decades that snowball dominates your final balance. Enter your initial investment, monthly contribution, expected annual rate and time horizon, and this free calculator projects your balance year by year.
The projection separates your total contributions from the interest earned, so you can see exactly how much of the final number is growth. All math runs instantly in your browser — no account, no data stored.
Year-by-year projection
A detailed breakdown table shows your balance, contributions and interest earned for every year, so the power of compounding is visible, not abstract.
Test what-if scenarios
Change the rate, monthly contribution or time horizon and watch the final balance update instantly — the fastest way to feel why starting early beats saving more later.
Illustration, not advice
Projections assume a constant annual return, which real investments never deliver. Use the results to understand compounding and set savings goals — not as a prediction or financial advice.
How to use
- Enter your initial investment amount.
- Add your planned monthly contribution.
- Set the expected annual interest rate and number of years.
- Click Calculate Growth to see the year-by-year projection.
Frequently Asked Questions
How does compound interest work?
Interest is calculated on your balance, which includes previously earned interest. Each period the base grows, so growth accelerates over time — the longer the horizon, the bigger the effect.
What is the formula for compound interest?
With monthly contributions the future value combines the compounded initial amount and the future value of an annuity: FV = P(1+r)^n + PMT x (((1+r)^n - 1) / r).
Should I use nominal or real returns?
Use the rate you expect your investment to earn. To estimate purchasing power, subtract expected inflation from the nominal return first.
Does this account for taxes or fees?
No. The projection is before taxes, fees and inflation. Real-world results will be lower — treat the number as an illustration of compounding, not a guarantee.
Is my financial data stored?
No. All calculations happen locally in your browser and nothing you enter leaves your device.
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