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Compound Interest Calculator

See how an investment grows over time with compound interest and optional regular monthly contributions.

100% client-side · nothing is uploaded

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How to use the Compound Interest

Fill in each input field with your own numbers.
Results calculate automatically and update as you change any value.
Read the result cards below the inputs for the full breakdown.
Adjust any field to explore different scenarios instantly.

Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.

About Compound Interest

The power of compounding

Compound interest earns interest on your interest, so growth accelerates over time. Starting early matters more than the rate.

Contributions

Adding a regular monthly amount dramatically increases the final value, because each contribution also compounds.

What you see

Enter the principal, annual rate, term, compounding frequency and monthly contribution to see the future value, total contributed and interest earned.

Frequently asked questions

What is compound interest?

Interest calculated on the original amount plus all previously earned interest.

How often should interest compound?

More frequent compounding yields slightly more; monthly is common for savings.

Are these guaranteed returns?

No — it is a projection assuming a fixed rate; real investments vary.