Understanding CAGR

CAGR (Compound Annual Growth Rate) answers 'what steady annual return, compounded, would have produced this same total result?' An investment that grew from $1K to $2.1K over 6 years has a CAGR of about 12.2% — even if the actual path was bumpy: up 40% one year, down 10% another, and so on.

This smoothing is exactly what makes CAGR useful for comparing two very different investments over the same period — a fund, a fixed deposit, gold — on a like-for-like basis, without needing to eyeball a year-by-year table of returns.

It's also exactly what can mislead. Two funds can have identical CAGR over 5 years while having wildly different volatility along the way — one might have swung 30% both directions, the other stayed within a narrow 8% band. CAGR alone tells you nothing about that ride, which matters enormously if you might need the money before the full period is up.

CAGR is also sensitive to the exact start and end dates chosen. A CAGR calculated from a market bottom to a market peak will look far better than the same fund's CAGR measured from peak to peak — always check what period is being used before comparing CAGR figures across sources.

A quick way to feel what a CAGR means is the rule of 72: divide 72 by the annual rate to estimate the years needed to double your money. At 12% that is about 6 years, which matches the $1K to $2.1K example above. At 7%, like many fixed deposits, doubling takes roughly 10 years. It's an approximation, not an exact figure, but it makes rates easy to compare mentally.

CAGR also helps you compare investments held for different lengths of time. A fund that turned $1K into $1.9K in 5 years has a CAGR of about 12.5%. One that turned $1K into $2.3K in 8 years sounds better, but its CAGR is only about 10.4%. The bigger total came from more time, not a better rate. Whenever a total gain is quoted without a period, ask for the CAGR before drawing conclusions.

Use CAGR for a single lump-sum investment held untouched. For monthly SIPs, where money goes in at different dates, the correct measure is XIRR, which weights each instalment by how long it was invested. And because CAGR compares only two points, look at rolling returns as well: the CAGR for every possible 3- or 5-year window. If a fund's rolling returns stay steady across many windows, its record is far more convincing than one impressive start-to-end figure.