Definition

PEG Ratio (Price/Earnings-to-Growth) is calculated by dividing a stock's P/E ratio by its annual earnings per share (EPS) growth rate, producing a single number that shows whether a stock's valuation is justified by its growth speed — a lower PEG indicates more value per unit of growth purchased.

Source: Lynch, P. (1989). One Up on Wall Street. Popularized the PEG ratio as a key screening metric.

Peter Lynch popularized PEG as the solution to P/E’s blind spot: P/E alone cannot distinguish between a P/E 40 stock growing 40% annually and a P/E 40 stock growing 5% annually. PEG collapses that distinction into a single comparable number. The first stock has PEG 1.0 (fair value); the second has PEG 8.0 (severely overvalued for its growth).

How PEG Is Calculated

PEG = P/E Ratio ÷ Annual EPS Growth Rate (%)

Example:

  • Stock price: $100
  • EPS (TTM): $4.00 → P/E = 25
  • EPS growth rate (next 3–5 years estimate): 20%
  • PEG = 25 ÷ 20 = 1.25 (slightly expensive but reasonable)

Growth rate used in the denominator can be:

  • Forward 1-year estimate (most common, most volatile)
  • 3–5 year average consensus (more stable, preferred for long-term analysis)
  • Trailing 3-year actual (backward-looking, more reliable but stale for accelerating growers)

PEG Interpretation Reference

Below 0.5
Deeply undervalued
Rare; verify growth estimate
0.5 – 1.0
Undervalued
Growth not fully priced in
1.0 – 1.5
Fair value
Market pricing growth fairly
1.5 – 2.0
Slightly expensive
Growth premium being paid
Above 2.0
Expensive
Growth priced in and then some

PEG vs P/E: Where PEG Wins

StockPriceP/EEPS GrowthPEGVerdict
Fast Grower A $200 50 50%/yr 1.0 Fair value
Slow Grower B $50 15 5%/yr 3.0 Expensive for its growth
Value Stock C $80 12 15%/yr 0.8 Undervalued — growth not priced in

Using P/E alone, Stock B looks cheapest (P/E 15) and Stock A looks most expensive (P/E 50). PEG reveals the opposite: Stock A is fairly valued; Stock B is actually the most expensive relative to what it delivers.

How to Use PEG for Stock Screening

Step 1 — Filter by PEG below 1.5. Run a screen for stocks with PEG < 1.5 in your target sector. This identifies companies where growth is not fully priced in.

Step 2 — Verify the growth estimate. PEG is only as reliable as the growth rate in the denominator. Confirm the estimate is from a credible consensus of 5+ analysts. A single bullish analyst outlier can distort the screen.

Step 3 — Check earnings consistency. PEG is meaningless if earnings are volatile quarter-to-quarter. Look for companies with consistent sequential EPS growth over at least 3 consecutive quarters.

Step 4 — Compare within sector. PEG of 1.2 in software is different from PEG 1.2 in healthcare. Each sector has its own typical PEG range — benchmark within sector.

Step 5 — Pair with free cash flow. Earnings can be manipulated; free cash flow cannot. Confirm that the growth in EPS is backed by actual cash generation.

Common Mistakes

✗ Mistake 1

"PEG below 1 always means buy."
PEG can be artificially low if analysts are modeling temporarily high growth. A company in a one-time earnings spike will show PEG 0.3 that reverts to 3.0 next year. Always verify multi-year growth sustainability.

✗ Mistake 2

"I use PEG on all stocks."
PEG is unreliable for companies growing below 10% (denominator too small, inflating PEG), negative EPS companies (no meaningful P/E), and mature dividend payers. Use price-to-cash-flow or dividend yield models for those categories.

✗ Mistake 3

"I use 1-year forward PEG for everything."
One-year forward estimates are the least reliable. Use 3-year consensus estimates for PEG calculation whenever available — they smooth over single-year misses and provide a more stable denominator.

Example: PEG Screening Identifies META’s Re-rating (2022–2023)

Case Study: PEG Identifies Undervaluation META · Year of Efficiency 2023
DatePriceP/EEPS Growth Est.PEGSignal
$90 11 12% (3-yr consensus) 0.9 🟢 PEG below 1.0 — market pricing in zero growth despite solid consensus estimates
$195 23 22% 1.05 PEG normalizing as market re-rates. Fair value.
$320 25 25% 1.0 Still fairly valued at PEG 1.0 despite 250% price gain from low.
Key Insight

META at $90 with PEG 0.9 was one of the most straightforward PEG-based buy signals of the decade. The market was pricing in near-zero growth; the consensus was modeling 12%+ growth for three years. The PEG signal resolved with a 255% rally as the market re-rated META back to fair value.

How Cluenex Displays PEG

Cluenex displays PEG ratio alongside P/E, earnings growth rate, and the full financial metrics suite for every covered stock. The combined view lets you verify whether a stock’s valuation is growth-justified or stretched — in one screen, without manual calculation.

Cluenex AI also ingests PEG as one of its inputs when calculating predicted short-term and long-term price movement, weighting stocks with sub-1.0 PEG and improving earnings revisions as higher-probability bullish setups in the AI’s valuation models.

Frequently Asked Questions

  • Who invented the PEG ratio? Peter Lynch popularized PEG in his 1989 book One Up on Wall Street, describing it as his preferred way to quickly assess whether a growth stock was reasonably priced. Mario Farina described a similar concept earlier in 1969, but Lynch’s version became the industry standard.

  • What is a good PEG ratio for tech stocks? Tech stocks typically trade at PEG 1.2–2.0 during bull markets. PEG below 1.0 in tech is rare and usually a strong buy signal. PEG above 2.5 in tech indicates the market is paying a significant premium over justified growth — proceed with caution on any earnings miss.

  • Can I use PEG on dividend stocks? Poorly. PEG was designed for growth companies. For dividend stocks, the relevant metric is the dividend discount model or price-to-cash-flow, not PEG. A utility company growing EPS 3% annually will always show a high PEG regardless of whether it’s cheap.

  • What growth rate should I use — forward or trailing? Use the 3–5 year consensus forward estimate from multiple analysts. Single-year estimates are too volatile. Trailing growth rates are reliable but may miss inflection points in accelerating companies.

  • Is PEG better than P/E? PEG is better for comparing companies across different growth rates. P/E is better for within-sector comparisons where growth rates are similar. For most stock screening, PEG is the more useful first filter because it prevents overpaying for slow growers disguised as value stocks.