PEG Ratio Explained

The answer in plain English

The PEG ratio divides a stock's P/E ratio by its expected earnings growth rate, providing a valuation measure that accounts for growth.

Simple answer

The PEG ratio divides a stock's P/E ratio by its expected earnings growth rate, providing a valuation measure that accounts for growth.

Why this matters

Two companies can have the same P/E ratio but very different growth prospects. The PEG ratio helps you compare them fairly by adjusting price for growth.

Good signs

A PEG ratio below 1.0 may suggest the stock is undervalued relative to its growth rate.

Warning signs

A PEG ratio above 2.0 may suggest the stock is expensive even after accounting for growth.

Easy mistake to make

Using inconsistent growth estimates, or treating the ratio as a precise signal rather than a rough guide.

How Wall Street Score helps

While WallStreetScore doesn't display PEG directly, its valuation category incorporates growth-adjusted metrics.

What Is the PEG Ratio?

The PEG ratio (Price/Earnings-to-Growth) is a valuation metric that adjusts the traditional P/E ratio by factoring in the company's expected earnings growth rate. The formula is simple: PEG = P/E Ratio ÷ Annual Earnings Growth Rate (as a percentage).

For example, if a stock has a P/E of 20 and expected earnings growth of 15% per year, the PEG ratio is 20 ÷ 15 = 1.33. A commonly cited rule of thumb is that a PEG below 1.0 suggests undervaluation, while a PEG above 1.5 may indicate the stock is richly priced relative to its growth.

Why Growth Matters in Valuation

The P/E ratio tells you how much you're paying per dollar of current earnings, but it says nothing about whether those earnings are growing or shrinking. A company with a P/E of 30 might seem expensive — but if earnings are growing at 30% per year, the company could be reasonably valued. A company with a P/E of 10 might seem cheap, but if earnings are declining, it could be a value trap.

The PEG ratio addresses this by dividing price by both earnings and growth. It gives you a single number that reflects both how much you're paying and how fast the business is growing. This makes it easier to compare companies with different growth profiles.

However, the PEG ratio is only as good as the growth estimate behind it. Analyst projections can be wrong, and growth rates can decelerate unexpectedly. Use the PEG as one input among many, not as a standalone buy signal.

Limitations of the PEG Ratio

While the PEG ratio is a useful tool, it has several important limitations:

First, growth estimates are uncertain. The ratio depends on projected earnings growth, which may not materialize. Companies in fast-changing industries are particularly prone to growth surprises — both positive and negative.

Second, the PEG ratio doesn't account for risk. A company growing at 20% with low risk and one growing at 20% with high risk may have the same PEG, but they are not equally attractive investments.

Third, the ratio doesn't consider dividend yield. A company that pays a substantial dividend may be more attractive than its PEG suggests, because total return includes both price appreciation and dividends.

Finally, PEG is less meaningful for companies with negative or erratic earnings. If earnings are near zero or negative, the ratio becomes distorted or uncalculable.

Apply this to a real stock

Use Wall Street Score to search a company and compare its score with revenue, earnings, cash, debt, valuation and risks.

Browse the stock directory or search from the homepage.