How is this calculated?

The simulation runs period by period, where each period is one compounding interval (one month for monthly compounding, one day for daily, and so on). Each period, the balance grows by the annual rate divided by the number of periods per year. Monthly contributions are added at the end of each compounding period — so they start earning interest from the next period onward. The yearly table aggregates those periods into one row per year.

What does compounding frequency change?

It changes how often earned interest starts earning its own interest. More frequent compounding gives a slightly higher final balance at the same stated rate, because each round of interest joins the balance sooner. The difference is modest for typical rates — compounding matters far more than how often it happens.

Does this include tax or inflation?

No. The numbers are nominal — before any tax you might owe on gains, and not adjusted for inflation. Your real purchasing power will be lower than the headline figure shows, especially over long periods.

Is this financial advice?

No. This is a math tool that shows how compounding works with a constant rate. It doesn't know your goals, risk tolerance, or situation, and it isn't a recommendation to invest anything, anywhere. For real decisions, talk to a qualified financial adviser.

Compound Interest Calculator

See what your money becomes when interest earns interest — with a year-by-year breakdown you can actually read.

Private by design: this tool runs entirely in your browser. Your files are never uploaded to a server, and nothing is stored.

Initial amount

Annual interest rate (%)

Years

Monthly contribution

Compounding

—

Projected balance

You put in	—
Interest earned	—

Year by year

Year	Start	Contributions	Interest	End

A projection with a constant rate — not a promise, and not financial advice.

How to use it

Enter your scenario. Starting amount, expected annual interest rate, and how many years you plan to let it grow.

Add contributions and compounding. An optional monthly contribution, and how often interest compounds (monthly is the usual default).

See the growth. Your projected balance, how much of it is your own money versus earned interest, and a year-by-year breakdown.

Why compound interest matters

Compound interest is interest that earns its own interest. Each time your balance is credited, the next round of interest is calculated on a slightly bigger number — your original money plus everything earned so far. Over time that snowball effect is what makes invested money grow faster than the rate alone suggests.

Time is the fuel. Because each year's growth builds on all previous growth, starting earlier means your money compounds for longer — even small amounts get more turns at the snowball. This calculator shows the mechanics of that process.

Remember: this is a projection, not a promise. Real returns move up and down, and no tool can predict markets, tax changes, or what you'll actually earn. Use it to explore scenarios, not to plan your life around a number.

Compound Interest Calculator

Year by year

How to use it

Why compound interest matters

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