Imagine you are looking at a local paint maker. The company proudly announces that its revenue has grown at a 20% Compound Annual Growth Rate (CAGR) over the last three years. It sounds like an incredible, smooth journey of wealth creation. But before you invest your hard-earned money, you need to look under the hood. CAGR is a powerful tool, but it is also a master of disguise. It can easily hide a messy, volatile reality behind a single polished number.

How to Calculate CAGR by Hand

CAGR is the imaginary, smoothed-out annual rate at which a business grows if it grows at a steady pace every single year. Because real businesses have good years and bad years, CAGR helps us compare them on an equal footing. To calculate a 3-year Revenue CAGR, you only need the starting revenue and the ending revenue.

Your result is a 20% CAGR. Anyone looking at this final number would assume the business is growing steadily. But let us look at how two different companies can arrive at this exact same destination.

The Trap of the Lumpy Path and Base Effects

Because CAGR only cares about the start point and the end point, it completely ignores the path taken in between. This is where retail investors get fooled by 'lumpy' growth or a 'low base effect' (where a single terrible starting year makes future growth look artificially spectacular).

Look at Company B. It suffered a major drop in Year 1, recovered slightly in Year 2, and then had a massive, one-off surge of 92% in Year 3. This single lucky year dragged the entire 3-year CAGR up to 20%. If that one-off surge was due to a temporary supply shortage or a single massive government order, Company B's growth is highly unlikely to continue. Company A, with its predictable, steady 20% year-on-year gains, is a far more stable business.

The Warning Signal: Decelerating Growth

The most critical signal to watch is the trend of year-on-year growth. A healthy company shows stable or accelerating growth. A dying business model often shows decelerating growth—for example, growing 15% in Year 1, then 12% in Year 2, and down to 9% in Year 3. Even if the overall 3-year CAGR still looks respectable, this downward trend is an early warning sign that the company is losing its competitive edge or its market is becoming saturated.

Sanity-Checking the Numbers

How do you judge if a CAGR is actually good? As a rule of thumb for Indian companies, compare the growth against the broader economy, peers, and the industry average. If a company is outgrowing its industry, it is gaining market share. Use these rough bands to guide you:

• 5% to 10%: Typical for mature, slow-moving industries (like utilities or traditional manufacturing).
• Above 10%: Good, solid growth.
• Above 15%: Strong growth, common in expanding sectors.
• Above 25%: Excellent, but you must ask if it is sustainable.
• Above 30%: Exceptionally rare over the long term. Always sanity-check very high CAGRs. They are often caused by a temporary industry tailwind or a low starting base, rather than a sustainable business model.

You can easily check any Indian company's 3-year and 5-year Revenue CAGR, and view its year-on-year growth trend, by searching for the stock on stock-analyze.com.