What is the PEG Ratio?
The PEG ratio (Price/Earnings to Growth ratio) is a stock valuation metric that relates a company's P/E ratio to its expected earnings growth rate. Developed by legendary investor Peter Lynch, the PEG ratio helps investors determine whether a stock is overvalued or undervalued by factoring in growth expectations.
While the P/E ratio tells you how much you're paying for current earnings, the PEG ratio tells you how much you're paying for future earnings growth. This makes it particularly useful for comparing growth stocks that might have high P/E ratios but also high growth potential.
How to Calculate PEG Ratio
The PEG ratio formula is:
PEG Ratio = P/E Ratio ÷ Earnings Growth Rate
Or equivalently:
PEG = (Stock Price ÷ EPS) ÷ Annual Growth Rate (%)
Example: If a stock trades at $150 per share, has EPS of $5.00, and projected earnings growth of 15%:
P/E = $150 ÷ $5.00 = 30x
PEG = 30 ÷ 15 = 2.0
How to Interpret PEG Ratio
Understanding what different PEG values typically indicate:
- PEG < 1.0: The stock may be undervalued relative to its growth rate. The market might not be fully pricing in the company's growth potential. This is often considered a buying signal by growth investors.
- PEG = 1.0 - 1.5: The stock is fairly valued. The price reasonably reflects the expected earnings growth. Peter Lynch considered a PEG of 1.0 to be "fair value."
- PEG = 1.5 - 2.0: The stock may be slightly overvalued. Investors are paying a premium for growth. The company needs to meet high expectations.
- PEG > 2.0: The stock may be significantly overvalued. Very high growth expectations are priced in. Consider whether growth projections are realistic.
PEG Ratio vs P/E Ratio
The key difference between PEG and P/E is the growth component:
| Metric | P/E Ratio | PEG Ratio |
|---|---|---|
| Formula | Price ÷ EPS | P/E ÷ Growth Rate |
| Considers Growth | No | Yes |
| Best For | Comparing similar companies | Comparing growth stocks |
| Fair Value | Varies by industry | Around 1.0 |
Limitations of PEG Ratio
While PEG ratio is valuable, it has important limitations:
- Growth estimates are uncertain: PEG relies on projected growth rates, which can be inaccurate or overly optimistic.
- Not suitable for all companies: PEG doesn't work for companies with negative earnings or declining growth.
- Ignores risk factors: Two companies with the same PEG may have very different risk profiles, debt levels, or competitive positions.
- Cyclical businesses: PEG can be misleading for companies with volatile earnings cycles.
- Different growth periods: Using 1-year vs 5-year growth rates can give very different PEG values.