Peter Lynch PEG Ratio — Formula & How to Use It
The shortcut Lynch popularized for judging whether growth is fairly priced: PEG = P/E ÷ growth rate — plus his dividend-adjusted version and the classic pitfalls.
The formula Lynch popularized
PEG = P/E ratio ÷ annual earnings growth rate (as a whole number). Lynch's rule of thumb in One Up on Wall Street: "The P/E ratio of any company that's fairly priced will equal its growth rate." A PEG of 1 means growth is fairly priced; well below 1 suggests you may be getting growth at a discount.
Lynch's refinement for income stocks adds the dividend: (growth rate + dividend yield) ÷ P/E. He looked for this ratio above 2 — letting steady dividend payers compete with fast growers on equal footing.
Reading the PEG
| PEG | Lynch's reading | Example |
|---|---|---|
| < 0.5 | Potentially very attractive — verify the growth is real | P/E 10 with 20% growth |
| ≈ 1.0 | Fairly priced growth | P/E 15 with 15% growth |
| 1.5–2.0 | Paying up — the story must be exceptional | P/E 30 with 17% growth |
| > 2.0 | Lynch: "generally a poor deal" | P/E 40 with 15% growth |
Bands are interpretive heuristics from Lynch's writing, not mechanical buy/sell rules.
Pitfalls Lynch warned about
- Garbage growth in, garbage PEG out: use a sustainable multi-year growth estimate, not last year's spike.
- Cyclicals break the PEG: peak earnings make P/E look low exactly when the cycle is about to turn.
- Very high growth rates rarely persist — applying 30%+ for a decade is how PEG flatters overpriced stocks.
- Compare within sectors: capital intensity and margins make cross-industry PEGs misleading.
- PEG is a first filter; Lynch still demanded the two-minute story, the balance sheet, and category awareness.
The $25 million lesson that changed Buffett
In 1972 the sellers of See's Candies asked $30 million; Buffett, trained on Graham's cigar butts, refused to go above $25 million — roughly three times book value, a price the old Buffett would never pay. The deal nearly died over $5 million. Charlie Munger pushed back: a beloved brand with loyal customers and genuine pricing power deserved a premium.
They paid the $25 million. See's went on to ship more than $1.65 billion of cumulative pre-tax earnings back to Omaha while needing almost no additional capital — raising prices every year without losing a single loyal customer. Buffett later called it 'the prototype of a dream business' and credits this one purchase with rewiring how he invests.
Quality compounds quietly for decades. Temperament and a clear circle of competence beat chasing the cheapest price.
The only deal Munger ever pushed
In the depths of the 2008 crisis, Munger did something he had never done before: he actively lobbied Buffett to invest in BYD, a Chinese battery and car maker led by engineer Wang Chuanfu — a man Munger described as "a combination of Thomas Edison and Jack Welch". The conviction came through Li Lu, whose circle of competence covered what Omaha's did not.
Berkshire paid $232 million for about 10% of the company — a tiny position by its standards, in an industry Buffett had publicly sworn off. At its 2022 peak the stake was worth roughly $9 billion, close to a forty-fold gain, before Berkshire began trimming.
A circle of competence can be extended honestly — by trusting someone who genuinely has one where you do not.
Related tools
Frequently asked questions
Did Peter Lynch invent the PEG ratio?
He popularized it in One Up on Wall Street (1989). The concept circulated among analysts earlier (often credited to Mario Farina's 1969 book), but Lynch made it a household tool.
Which growth rate should I use?
A conservative estimate of sustainable earnings growth over the next 3–5 years. Analyst long-term estimates or a normalized historical rate are common starting points; avoid one-off recovery years.
Does the PEG work for dividend stocks?
Use Lynch's adjusted version: (growth + dividend yield) ÷ P/E, seeking values above 2. It credits slow growers for the cash they actually pay you.
Valuefocus surfaces P/E, growth, and PEG context for any stock — so the shortcut comes with the full picture.
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