Compound Interest Calculator

Use it when you want to test the exact inputs on this page: Estimate how compound interest can grow savings over time. Compare monthly deposits with a starting amount. The result is a check against your assumptions, not proof that a lender, tax app, broker, platform, or provider will use the same number.

Money tools are picky about labels. Dollar fields should be entered as dollar amounts, rate fields should be entered as percentages like 6.5 instead of 0.065, and term fields should match the page label such as months or years. If a field says monthly, do not enter a yearly total unless the tool specifically asks for it.

In plain language: The calculator converts the stated annual rate to an effective monthly growth rate from the selected compounding frequency, then compounds principal and monthly deposits. If the result seems too high or too low, first check whether each field expects a monthly amount, annual amount, dollar value, or percent.

Start with the headline number, then use the supporting lines to see why the answer moved. For finance calculators, the extra lines often explain interest, tax, fees, principal, payment timing, or totals paid over time. Those pieces matter because two results can look close at first but cost very different amounts later.

This calculator gives an educational estimate only. It does not include every fee, lender rule, tax rule, local rate, credit, penalty, or personal financial detail. Real finance decisions can also depend on fees, timing, local rules, credit details, and provider-specific terms.

Check the rate, time period, compounding or payment frequency, and whether the value is before tax or after tax. A common mistake is mixing monthly and yearly numbers, which can make a finance answer look believable even when it is off by a lot.

No. The calculator runs in your browser tab. Recent answers stay only on the page while you use it, and they are not sent to a server.