What PEG means

P/E told us how many years of current earnings the market is charging for. It never asked how fast those earnings are growing — and a 30x P/E on a company doubling profit every couple of years is a very different proposition from a 30x P/E on one barely growing at all. PEG — price/earnings-to-growth — divides P/E by the earnings growth rate to put that question front and centre.

The formula

PEG = P/E / Earnings Growth Rate (%)

A PEG below 1 is the classic “growth at a reasonable price” heuristic — the P/E looks justified, or even cheap, relative to how fast earnings are growing. This series uses each company’s single most recent year of PAT growth (FY24 to FY25) as the growth figure — a simplification worth watching closely in the second example below. Strictly, PEG usually uses EPS (earnings per share) growth. That equals PAT (profit after tax) growth only when the share count is stable, as at Britannia; Desi Bites’ IPO added shares, so its per-share growth is lower than the PAT growth used here.

Worked example: Desi Bites Foods Ltd

   
P/E (from the P/E post) 38.3x
÷ PAT Growth, FY24→FY25 49.3%
PEG 0.78

A PEG of 0.78 — comfortably under 1 — reads as a classic growth-at-a- reasonable-price small-cap story: a rich-looking P/E that’s actually backed by real, fast profit growth.

Worked example: Britannia Industries

Same 30 June 2025 price and FY25 figures used throughout this module — audited consolidated FY25 results. For illustration only.

   
P/E (from the P/E post) 64.7x
÷ PAT Growth, FY24→FY25 1.8%
PEG 35.9

A PEG of 35.9 looks absurd — and it is, but not because Britannia is a bad business. It’s because FY25 happened to be a genuinely weak single-year growth year (remember the margin compression from earlier in this series) — dividing a high P/E by a growth rate close to zero produces a wildly unstable number. This is exactly the failure mode PEG is known for: it leans entirely on one growth figure, and a single unusually slow (or unusually fast) year can make an otherwise reasonable P/E look absurd, or an otherwise expensive one look cheap. Professional use of PEG typically substitutes a multi-year CAGR (compound annual growth rate — the steady yearly rate that would take you from the starting figure to the ending one) or a forward growth estimate instead of one year’s number — this series used a single year deliberately, to make that weakness visible rather than hide it.

Common mistakes

  • Using a single year’s growth rate, as shown starkly above. A multi-year CAGR, or a forward estimate, smooths out the kind of one-year noise that made Britannia’s PEG here practically meaningless.
  • PEG breaking down entirely at low or negative growth. Dividing by a small or negative number produces wild, uninterpretable results — PEG simply isn’t a usable tool for companies with near-zero or shrinking earnings in the period being measured.
  • Treating PEG below 1 as automatically cheap. It still matters how that growth was achieved — growth funded by deteriorating margins or unsustainable debt is a very different story from genuinely accretive growth, even at an identical PEG.
  • Comparing PEG across sectors with different natural growth rates and valuation norms. A “normal” PEG for a fast-growing small-cap and a mature large-cap aren’t the same number.

Takeaway: PEG asks whether a P/E is justified by growth, but it’s only as good as the growth figure behind it. One weak year, like Britannia’s here, can make the number meaningless — so treat it as a starting question, not a verdict.