1. Why P/E Alone Isn't Enough
The P/E ratio is the most popular valuation metric, but it has a blind spot: it ignores growth. A company growing earnings at 40% a year deserves a higher P/E than one stuck at 3% — yet P/E treats them the same.
The PEG ratio (Price/Earnings-to-Growth) fixes this by dividing P/E by the earnings growth rate. It turns "expensive" and "cheap" into something you can compare across fast- and slow-growing companies.
2. The PEG Formula
Consider two stocks. Stock A has a P/E of 30 and grows earnings at 30% a year, giving a PEG of 1.0. Stock B has a P/E of 15 but grows at just 5%, giving a PEG of 3.0.
On P/E alone, Stock B looks half as expensive. But adjusted for growth, Stock A is the better value — you pay far less for each unit of growth. That is the entire point of the PEG ratio.
3. How to Interpret PEG
PEG < 1.0
Potentially undervalued relative to growth
PEG ≈ 1.0
Fairly valued for its growth rate
PEG > 2.0
Potentially overvalued relative to growth
The rule of thumb is that a PEG of 1.0 marks fair value — the market prices the stock in line with its growth. Below 1.0 may be a bargain; above 2.0 suggests overpaying for the growth you get.
4. Peter Lynch and the PEG Rule
Legendary Fidelity fund manager Peter Lynch popularized the PEG ratio in One Up on Wall Street. He argued that "the P/E ratio of any company that's fairly priced will equal its growth rate" — a PEG of 1.0.
Lynch's insight: A company growing at 20% with a P/E of 20 (PEG 1.0) is a far better bargain than one growing at 10% with a P/E of 20 (PEG 2.0). He hunted for fast growers trading at a PEG well below 1.0.
5. Limitations of the PEG Ratio
Growth estimates are guesses
PEG relies on projected growth, which analysts frequently get wrong. A rosy forecast makes any stock look cheap.
Not for slow or cyclical companies
For firms with near-zero or erratic growth, dividing by a tiny growth number produces a wildly inflated PEG that means nothing.
Ignores risk and quality
A low PEG doesn't tell you whether that growth is sustainable, debt-fueled, or high-risk. Pair it with balance-sheet and cash-flow checks.
6. Using PEG on WIT
WIT stock pages show the P/E ratio and earnings growth you need to estimate PEG. To apply it:
- Find the P/E and EPS growth for a stock on the dashboard.
- Divide P/E by the growth rate to get a rough PEG.
- Compare growth stocks fairly — PEG lets you rank a 40%-grower against a 10%-grower on equal footing.
- Confirm the growth is real with our free cash flow and income statement guides.