What this tool does
This Compound Interest Calculator shows how a lump sum grows when interest is added back and earns more interest over time. It is handy for savers comparing accounts, investors estimating long term returns, students learning the formula, and anyone who wants a quick, honest picture of future value. Instead of guessing, you get the final balance, the total interest earned, and a reminder of how much was your original deposit.
How to use it
- Enter your starting amount in the Principal field.
- Type the yearly rate in the Annual rate (%) field, for example 5 for five percent.
- Set how long the money stays invested in the Years field.
- Choose how often interest is added in the Compounded frequency menu (annually, semiannually, quarterly, monthly, or daily).
- Select Calculate to see your final balance, total interest, and principal.
A quick worked example
Put in 1000 as your Principal, set the Annual rate (%) to 5, enter 10 in Years, and pick monthly in Compounded frequency. The balance grows to about 1647, meaning roughly 647 in interest on top of your original 1000. Try switching the frequency to annually or daily to see how the result shifts slightly, a clear way to understand why compounding matters.
Everything runs right in your browser, so your numbers stay private and never leave your device. It is completely free and needs no sign-up.
Frequently asked questions
- How is compound interest different from simple interest?
- Simple interest is earned only on your original principal, while compound interest is earned on the principal plus any interest already added. Over time, compounding grows your balance much faster.
- Does compounding frequency really matter?
- Yes, but the effect is smaller than many people expect. More frequent compounding (monthly or daily) earns slightly more than annual compounding at the same rate, with the gap widening over longer periods.
- What rate should I enter?
- Enter the annual interest rate as a percent, for example 5 for five percent. Use the nominal yearly rate quoted by your bank or account, and the calculator applies it across the frequency you choose.
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Last updated: June 17, 2026