Is the compound interest calculator free?

Yes — 100% free, no signup, no usage limits.

Does it save my data?

No. Inputs are processed in your browser and never uploaded to a server.

Can I use it on mobile?

Yes. The interface is fully responsive and works on iOS and Android.

What's the compound interest formula?

A = P(1 + r/n)^(nt) for a lump sum; with monthly contributions, the future value of an annuity is added. This tool simulates period-by-period to handle both.

Compound Interest Calculator

Project investment growth with monthly contributions, custom compounding, and a yearly chart.

Principal ($)Annual rate (%)YearsMonthly contribution ($)

Compounded

Final balance

$144,573

Total contributions

$58,000

Interest earned

$86,573

Growth over time

Year 1 → Year 20

How to use

Step 1: Enter principal, rate, and years
Step 2: Add your monthly contribution
Step 3: Pick compounding frequency
Step 4: Read final balance and interest earned

Frequently asked questions

Compound interest is interest on interest — the engine behind long-term investing.