Compound Interest

PPF gives guaranteed 7.1% tax-free returns. SIP in equity mutual funds has historically returned 12–14%. But which one actually puts more money in your pocket after 15 years, after accounting for taxes, inflation, and risk? We run the numbers.

CAGR — Compound Annual Growth Rate — is the most honest way to measure how an investment has grown over time. It smooths out volatile year-to-year swings into a single, comparable annual rate. This guide explains the formula, shows real examples, and explains why CAGR can also be misleading.

Both earn interest on a principal — but compound interest earns interest on the interest too. After 20 years, the difference is staggering. Here is the side-by-side math.

The Rule of 72 is a mental math shortcut used by investors worldwide. Divide 72 by your annual return and you get the number of years it takes your money to double — no spreadsheet needed.

Compound interest is the single most powerful force in personal finance. Understand the formula, see how small differences in rate and time create massive differences in outcome, and learn how to use it to your advantage.