Math • Finance

Compound Interest Calculator

Project future value with compounding (annually to daily or continuous), regular contributions, APY and a year-by-year breakdown. Ordinary annuity vs due.

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Currency

Principal (initial)Annual rate %YearsCompoundingContribution per period

FrequencyTiming

Future value

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Total contributions

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Interest earned

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Future − contributions

Year	Balance	Contributions	Interest

A = P(1+r/n)^nt + PMT·[((1+r/n)^nt−1)/(r/n)] (× 1+r/n if due). Continuous: P·e^rt. APY = (1+r/n)ⁿ−1.

How to use

1Enter principal, annual rate % and years. Choose compounding frequency (or continuous).
2Add a periodic contribution, its frequency (monthly/yearly) and timing — end (ordinary) vs beginning (due).
3See future value, total contributions, interest earned, APY and the yearly table.

Formulas

A = P(1+r/n)^(nt) + PMT·[((1+r/n)^(nt)−1)/(r/n)] (×1+r/n if due) • Continuous: Pe^(rt) • APY=(1+r/n)^n−1

n=compounds/year, r=annual rate (decimal), t=years, PMT=periodic contribution. When contribution frequency differs from compounding, we simulate period-by-period. APY is the effective annual rate.

Examples

$10,000 at 6% compounded monthly for 10y

No contributions → 10000·(1+0.06/12)^120 = $18,193.97 (interest $8,193.97).

Future $18,193.97

Same + $100/month (end)

Monthly PMT annuity = $16,387.93 → total $34,581.87, contributions $22,000, interest $12,581.87. Due (beginning) would be ×1.005 higher.

Future $34,581.87

About

The Compound Interest Calculator projects how your savings grow when earned interest is reinvested. Enter a starting principal, an annual interest rate, the number of years, and a compounding frequency — from annually down to continuously — plus optional regular contributions and their timing. The result includes the future value, total contributions, interest earned, and APY, along with a year-by-year breakdown. Savers, investors, and students use it to compare growth scenarios, plan contributions toward a savings goal, and understand how compounding frequency and contribution timing shape long-term results.

Frequently asked questions

Ordinary vs due?

End-of-period is standard (contribution after interest). Beginning-of-period (annuity due) earns one extra compounding period, so it’s slightly higher (×1+r/n).

What is APY?

Annual Percentage Yield — the effective rate after compounding. 6% monthly ⇒ APY ≈ 6.17% ((1+0.06/12)^12−1).

Does this include taxes or inflation?

No — pre-tax, nominal dollars. Adjust rate for after-tax or real (net of inflation) estimates.

Disclaimer

Educational estimates only. Actual returns vary with fees, taxes and compounding dates. Not financial advice.

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