Fundamental analysis

PEG ratio

PEG ratio is a stock’s price-to-earnings ratio divided by its expected annual earnings-per-share growth rate expressed as a percentage, relating its valuation multiple to a growth estimate.

What it means

The price/earnings-to-growth (PEG) ratio puts a stock’s P/E multiple alongside an estimate of how quickly its earnings per share (EPS) may grow. It is a valuation comparison, not a measure of trading costs or a forecast that the share price will rise.

A PEG of 1 means the numerical P/E and the numerical growth rate are equal under the standard convention: for example, a P/E of 20 and expected growth of 20% per year. That does not establish that a stock is fairly valued. The result depends on the earnings figures, growth estimate, time horizon and accounting assumptions used.

How it is calculated

PEG ratio = P/E ratio ÷ expected annual EPS growth rate (in percentage points)

  • P/E ratio is share price divided by EPS for a stated period. It has no unit. Specify whether it uses trailing reported earnings or forecast earnings.
  • Expected annual EPS growth rate is the projected percentage change in EPS per year over a specified period. Enter 20 for 20% per year, not 0.20. If a forecast covers several years, the annualized compound growth rate can be used; identify the period.
  • PEG ratio is conventionally reported without a unit. Growth entered as a decimal requires a different numerical convention, so do not mix the two.

For forecasts spanning multiple years, an annualized rate can be calculated as (ending EPS ÷ starting EPS)^(1 ÷ number of years) − 1, then multiplied by 100 for use in the PEG formula. This calculation requires positive starting and ending EPS. Forecasts are estimates, not known future earnings.

Worked example

Suppose, hypothetically, a stock trades at US$40 per share, has US$2 of trailing EPS, and is expected to grow EPS by 10% per year over a stated future period.

  1. Calculate trailing P/E: US$40 ÷ US$2 = 20.
  2. Enter the expected annual growth rate as 10 percentage points, rather than 0.10.
  3. Calculate PEG: 20 ÷ 10 = 2.

This hypothetical stock has a PEG ratio of 2 under those assumptions. If the growth estimate changes while the P/E stays at 20, the PEG changes too. The calculation does not establish whether the stock is attractive or whether its earnings forecast will be met.

Why it matters before you trade

PEG can help frame a fundamental question: how much is reflected in the current earnings multiple relative to assumed EPS growth? Comparing two PEG figures is most meaningful when both use comparable earnings measures, forecast periods and growth methods. It is less informative when one estimate is based on next year’s growth and another on a longer annualized forecast.

Pre-trade analysis also needs to address a different question: what risks and costs might arise when placing a particular order? A valuation ratio does not capture the bid-ask spread, market impact, volatility, position size or concentration of a stock basket. Those considerations can matter regardless of a stock’s PEG.

How PreTrAIde uses it

The product facts do not list the PEG ratio as a PreTrAIde input, calculation or score. Do not treat a PreTrAIde verdict as a PEG assessment.

PreTrAIde is an AI pre-trade analysis platform for stocks. A user builds a basket with a side, quantity and execution conditions for each line. Before an order is placed, PreTrAIde returns GO, NO-GO or MODIFY verdicts for the basket and each line, alongside a model-estimated success probability, risk assessment, suggested execution strategy and plain-language reasoning. Its quantitative layer estimates measures including spread, market impact, daily volatility, liquidity and concentration. These checks address aspects of a proposed trade that PEG does not. Verdicts are decision support, not recommendations; users place any trades themselves through their own broker.

Common mistakes

  • Entering growth as a decimal: Dividing P/E by 0.10 instead of 10 makes the conventional PEG figure 100 times larger.
  • Treating forecasts as facts: A small change in an uncertain growth estimate can substantially change PEG.
  • Ignoring the earnings basis: Trailing and forward P/E ratios may produce different PEG figures for the same stock.
  • Using PEG with zero or negative growth: Division by zero is undefined; a negative result is usually not a useful valuation comparison.
  • Overlooking negative EPS: A conventional P/E, and therefore PEG, is generally not meaningful when EPS is zero or negative.
  • Reading PEG as an execution signal: It says nothing directly about the likely cost of filling an order.

Frequently asked questions

What does a PEG ratio of 1 mean?

Under the standard percentage-point convention, it means the numerical P/E equals the expected annual EPS growth rate: for example, 20 and 20%. It does not prove that the stock is fairly valued.

Should I use 10 or 0.10 for 10% growth in the PEG formula?

Use 10 when applying the conventional formula, which divides P/E by the growth rate expressed in percentage points. Using 0.10 without changing conventions produces a figure 100 times larger.

Can you calculate a PEG ratio when earnings are negative?

A conventional P/E is generally not meaningful with zero or negative EPS, so its PEG ratio is generally not meaningful either. Zero expected growth also makes the PEG calculation undefined.

Related terms

Price-to-earnings ratio (P/E) Price-to-earnings ratio (P/E) is a stock’s price per share divided by its earnings per share, showing how much investors pay for each dollar of reported earnings. Forward P/E Forward P/E is a stock’s current price divided by its estimated earnings per share for a specified future period, usually the next 12 months or fiscal year. Earnings per share (EPS) Earnings per share (EPS) is a company's profit available to common shareholders divided by its weighted-average common shares outstanding over a reporting period. Consensus estimate Consensus estimate is an aggregate of analysts’ forecasts for a company metric, such as quarterly earnings per share or revenue, for a specified reporting period. Stock valuation Stock valuation is the process of estimating what a company's shares are worth using its financial results, expected cash flows or comparisons with other companies. Pre-trade analysis Pre-trade analysis is the assessment of a proposed stock order or basket before placement, estimating execution costs, liquidity and risk to inform the investor’s decision and execution approach.

Fundamental analysis

Earnings Price-to-book ratio (P/B) EV/EBITDA Free cash flow Revenue Profit margin Earnings guidance Earnings surprise All glossary terms →

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Educational content, not investment advice. PreTrAIde is analysis software, not a broker: it never executes orders, and its verdicts are decision support, not recommendations to buy or sell.