Daily Figures Edition No Sign-Up • No Tracking • Free Forever Vol. XII — No. 204
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Compound Interest Calculator

Enter a starting amount, monthly contribution, rate and years to see the future value and interest earned.

Filed by The Statistics Desk  |  Method: compound + annuity future value
Future value
—
What it grows to.
Readout
Total contributions—
Interest earned—
Starting amount—
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Enter your figures above to see the step-by-step working.
Educational estimate — not investment adviceEverything computed client-side — nothing leaves this page

How the Compound Interest Calculator Works

Compound interest is interest earned on your interest. Each period, the rate is applied to everything you have — your original money plus all the interest already added — so the balance grows faster and faster. Over long horizons this snowball effect dwarfs the amount you actually put in.

Enter a starting amount, an optional monthly contribution, the annual rate, the number of years and how often interest compounds. The calculator grows the starting balance with the compound-interest formula and grows the stream of contributions with the future-value-of-an-annuity formula, then adds them. More frequent compounding earns slightly more.

FV = P(1 + r/n)nt + PMT · [((1 + r/n)nt − 1) ÷ (r/n)]

Frequently Asked Questions

What does compounding frequency change?

More frequent compounding (daily vs annually) adds interest to the balance sooner, so it starts earning its own interest sooner. The effect is real but modest — usually a fraction of a percent of the final value.

How are contributions treated?

The monthly contribution is added over time and each addition compounds from when it goes in. This calculator converts your monthly amount to match the compounding period and grows it as an annuity.

Why is compound interest so powerful?

Because growth builds on previous growth. Early money has the most time to compound, which is why starting sooner usually beats contributing more later.

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