PEG Ratio Explained

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

PEG makes the growth assumption explicit, but does not equalize risk, capital needs or the duration of growth.

Good signs

A lower PEG means a lower P/E relative to the chosen growth rate, not proof of undervaluation.

Warning signs

A higher PEG may reflect a lower growth estimate or a higher multiple. Neither alone establishes overvaluation.

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

Use PEG as a supplementary calculation alongside the valuation inputs shown on the stock page.

Keep the growth units and horizon explicit

Hypothetical P/E of 20 divided by expected annual EPS growth of 10 gives PEG of 2.0. Enter 10 for 10%, not 0.10. State whether the estimate covers one year or several years, and whether P/E uses trailing or forecast earnings.

Compare calculations using the same definitions. A short rebound after a loss is not interchangeable with a multiyear growth estimate.

Test the assumption before using a threshold

With P/E unchanged at 20, raising the growth estimate from 10% to 20% cuts PEG from 2.0 to 1.0. No change in the share price or reported earnings was necessary. The apparent improvement came entirely from a forecast.

There is no universal PEG threshold that establishes fair value. Consider how much investment the growth requires, how long it may last and what happens if it disappoints.

Recognize an unusable denominator

Zero growth makes the calculation undefined. Negative growth or negative earnings usually makes a conventional PEG comparison unhelpful; a negative number is not a bargain signal. Growth from a very small earnings base can also produce a misleadingly low ratio.

Check cash generation, debt and dilution separately. PEG does not incorporate all of those risks or measure total shareholder return.

Further reading and verification

• SEC: Beginner's Guide to Financial Statements

References explain the underlying concepts; they do not endorse Wall Street Score's model.

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.