TL;DR
The PEG ratio, price/earnings to growth, divides a stock's P/E ratio by its expected earnings growth rate to judge whether a high valuation is justified by fast growth. A PEG around 1 is often seen as fair value, well below 1 may signal a bargain, and well above 1 may signal an expensive stock. It bridges value and growth investing, but it leans on an uncertain growth forecast and ignores debt and dividends, so use it as a quick sanity check rather than a verdict on its own.
The PEG ratio, price/earnings to growth, compares a stock's price-to-earnings ratio to its expected earnings growth rate. It refines the P/E by asking whether a high valuation is justified by fast growth. A PEG around 1 is often seen as fair value; well below 1 may signal a bargain, and well above 1 may signal an expensive stock.
The appeal of the PEG is that it answers a question the raw P/E cannot: is this stock expensive for what it is, or expensive because it is growing quickly? A company on a steep multiple is not necessarily overpriced if its earnings are racing ahead, and the PEG is the simplest way to fold that growth into a single number. It is a favourite first screen for investors hunting undervalued stocks among fast growers.
The formula
The PEG ratio is the price-to-earnings ratio divided by the annual earnings growth rate, expressed as a whole number rather than a decimal. So a P/E of 20 with 20% expected growth gives PEG = 20 ÷ 20 = 1.0. The growth figure is usually the forecast annual rate over the next few years, and it is entered as the number (20), not the fraction (0.20).
Worked example. A stock trades at a P/E of 30 and is expected to grow earnings 30% a year. PEG = 30 ÷ 30 = 1.0, fairly priced for its growth. Another at a P/E of 30 growing only 10% has a PEG of 3.0, expensive.
Why it bridges value and growth
A plain P/E can make a fast grower look expensive and a stagnant company look cheap. The PEG corrects this by putting growth in the denominator, which is why value investors use it to judge whether paying up for growth is actually reasonable.
This is exactly the tension at the heart of the value-versus-growth debate: a strict value screen rejects high P/E names on sight, yet some of the best long-run compounders trade on rich multiples precisely because they keep growing. The PEG gives a value-minded investor a disciplined way to consider those companies, it accepts a high P/E only when the growth rate genuinely earns it, rather than ruling them out altogether.
Its limits
PEG relies on a growth forecast, which is uncertain and easily too optimistic. It also ignores debt and dividends. Treat it as a quick sanity check that sits alongside fuller methods like a DCF, not a verdict on its own.
The single biggest weakness is that the answer is only as good as the growth estimate feeding it: analysts tend to be optimistic, and a PEG that looks like a bargain can evaporate the moment growth disappoints. Because it leans entirely on forecasts and ignores the balance sheet, the PEG is best paired with a look at the company’s intrinsic value and its debt before you draw any conclusion. Use it to shortlist candidates, then do the deeper work.
When you want to put real numbers behind it, our PEG ratio calculator divides the P/E by your growth assumption for you, so you can test how sensitive the verdict is to the growth rate you feed in.
Open the PEG ratio calculator
Summary
The PEG ratio compares a stock's P/E to its earnings growth, helping judge whether a growth stock is fairly priced. Learn the formula and how to read it.
Written by
Federico RomaldiCo-Founder, Worthmap
Published: June 6, 2026
Federico is a co-founder of Worthmap, a wealth-intelligence platform built for serious investors. With a background in software engineering and a long-standing passion for value investing, he created Worthmap to bridge the gap between net-worth tracking and investment analysis.
Comments
Be the first to comment on this article.