Compound Interest Calculator

This calculator shows how a lump sum and optional monthly contributions could grow over time at a chosen interest rate, once that interest is reinvested and starts earning its own interest.

FAQ

Is this compound interest calculator free to use?

Yes. It runs entirely in your browser, needs no account and no payment, and the result updates instantly as you move the sliders.

What's the difference between simple and compound interest?

Simple interest is calculated only on your original amount each period. Compound interest is calculated on your original amount plus any interest already added, so the balance grows faster the longer it compounds.

Does monthly compounding always beat annual compounding?

For the same stated annual rate, compounding more often (e.g. monthly) produces a slightly higher balance than compounding annually, because interest is added to the balance sooner and starts earning its own interest sooner.

Can I include monthly contributions?

Yes, the calculator lets you add a recurring monthly contribution alongside your initial amount, and includes it in the growth chart and totals.

Are the results guaranteed?

No. This is an illustration based on the fixed rate and period you enter. Real interest rates change over time, and this tool does not predict future returns.

Illustration only. Not financial advice.