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Compound Interest Calculator

See how a lump sum grows with compound interest — and how the compounding frequency changes the result.

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How to use

  1. 1.Enter your starting principal and the annual interest rate.
  2. 2.Pick how often interest compounds — annually, semiannually, quarterly, monthly, or daily — and the number of years.
  3. 3.Read the final amount and the total interest earned, and switch the frequency to see the compounding effect.

About Compound Interest Calculator

The Compound Interest Calculator shows how a single lump sum grows over time when interest is reinvested and starts earning interest of its own. Enter your starting principal, an annual interest rate, how often the interest compounds (annually, semiannually, quarterly, monthly, or daily), and a number of years. The calculator instantly returns the final amount your money grows to and the total interest earned. Everything runs locally in your browser, so none of your figures are uploaded or stored.

This tool focuses on the growth of one principal, not on regular deposits. If you are planning to add money every month or year, use our savings calculator instead — it is built around recurring contributions. Here the star of the show is the compounding-frequency effect: the same principal, rate, and term can produce a noticeably larger balance simply because interest is credited more often. Each time interest compounds, it is added to the balance, and the next period's interest is calculated on that larger balance. More frequent compounding means interest starts earning interest sooner.

Under the hood the calculator uses the standard compound interest formula A = P(1 + r/n)^(nt). P is your principal, r is the annual rate written as a decimal, n is the number of times interest compounds per year, and t is the number of years. Daily compounding uses n = 365. The interest earned is simply the final amount minus the principal you started with. When the rate is 0%, there is no growth, so the final amount equals your principal and the interest earned is zero.

Try switching the frequency while keeping everything else the same. At a 10% annual rate on $1,000 over five years, annual compounding grows the balance to about $1,610.51, monthly to about $1,645.31, and daily to about $1,648.61. The gaps look small at first but widen with higher rates, larger balances, and longer horizons — which is exactly why the frequency matters. This is also the difference between a nominal rate and the effective annual rate (APY): more frequent compounding raises the effective yield above the stated nominal rate.

Use the calculator to compare savings accounts, certificates of deposit, bonds, or any investment quoted with a fixed rate and a stated compounding schedule. It assumes a constant rate, no additional deposits or withdrawals, and no taxes or fees, so it is a planning aid rather than a guarantee. Real returns vary, and tax treatment differs by account and country. Always confirm the exact terms with your bank or a licensed financial professional before making a decision.

Methodology & sources

The final balance uses the standard compound interest formula A = P(1 + r/n)^(nt), where P is the starting principal, r is the annual rate as a decimal (annualRatePct / 100), n is the number of compounding periods per year (Annually = 1, Semiannually = 2, Quarterly = 4, Monthly = 12, Daily = 365), and t is the number of years. Interest earned = A - P. Increasing n while holding P, r, and t constant raises A, because interest is credited more often and compounds sooner — the compounding-frequency effect that separates the effective annual yield (APY) from the nominal rate. When r = 0, A = P and interest earned = 0. The model assumes a fixed rate, no additional deposits or withdrawals, and no taxes or fees. Estimates are for general information only and are not financial advice.

Frequently asked questions

How is compound interest calculated?
It uses the formula A = P(1 + r/n)^(nt), where P is the principal, r is the annual rate as a decimal, n is the number of compounding periods per year, and t is the number of years. The interest earned is the final amount A minus the principal P. At a 0% rate the final amount equals the principal and no interest is earned.
Does compounding frequency really change how much I earn?
Yes. With the same principal, rate, and term, compounding more often produces a larger final balance because interest is credited sooner and starts earning interest of its own. Daily compounding beats monthly, which beats quarterly, which beats annual. The difference grows with higher rates, larger balances, and longer time horizons.
What is the difference between this and a savings calculator?
This calculator grows a single lump-sum principal and highlights the effect of compounding frequency, with no regular deposits. A savings calculator is built around recurring contributions — money you add every month or year — so use that one if you plan to keep depositing funds over time.

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