Compound Interest Calculator

Compound Interest Calculator projects how an investment grows when returns compound over time, taking principal, rate, duration, compounding frequency, and contributions, and separating your final value into what you put in versus what it earned.

Compounding is the engine of long-term investing: you earn returns on your returns, so growth accelerates and, over long horizons, the interest earned can dwarf your contributions. This is precisely why starting early is so powerful, time, more than the rate or even the amount, is the dominant lever, and the calculator makes that vivid.

Two factors fine-tune the result: more frequent compounding earns modestly more (returns start compounding sooner), and regular contributions add their own compounding streams. But read the output as a planning projection, not a promise, it assumes a steady return while markets vary, and it's nominal and pre-tax, so inflation and taxes lower your real outcome.

This variant is framed for investment and savings projections; the companion Compound Calculator covers the same maths more generally. It's not financial advice and runs in your browser. Pair it with the SIP, FIRE, and Retirement calculators for a full investment-planning toolkit.