It is common practice for investors to use the price-to-earnings ratio (P/E ratio or price multiple) to determine if a company's stock price is over or undervalued. Companies with a high P/E ratio are typically growth stocks. However, their relatively high multiples do not necessarily mean their stocks are overpriced and not good buys for the long term.

TUTORIAL: Understanding the P/E Ratio

Let's take a closer look at what the P/E ratio tells us:

P/E Ratio p/e ratio

There are two primary components here, the market value (price) of the stock and the earnings of the company. Earnings are very important to consider. After all, earnings represent profits, and that's what every business strives for. Earnings are calculated by taking the hard figures into account: revenue, cost of goods sold (COGS), salaries, rent, etc. These are all important to the livelihood of a company. If the company isn't using its resources effectively it will not have positive earnings, and problems will eventually arise. Learn more about how to use the price-to-earnings ratio to reveal a stocks real market value. Read Profit With The Power Of Price-To-Earnings.)

Besides earnings, there are other factors that affect the value of a stock. For example:

  • Brand - The name of a product or company has value. Established brands such as Proctor & Gamble are worth billions.
  • Human Capital - Now more than ever, a company's employees and their expertise are thought to add value to the company.
  • Expectations - The stock market is forward looking. You buy a stock because of high expectations for strong profits, not because of past achievements.
  • Barriers to Entry - For a company to be successful in the long run, it must have strategies to keep competitors from entering the industry. For example, most anyone can make a soda, but marketing and distributing that beverage on the same level as Coca-Cola is very costly.

All these factors will affect a company's earnings growth rate. Because the P/E ratio uses past earnings (trailing 12 months), it gives a less accurate reflection of these growth potentials.

The relationship between the price/earnings ratio and earnings growth tells a more complete story than the P/E on its own. This is called the PEG ratio and is formulated as:

PEG ratio
*The number used for annual growth rate can vary. It can be forward (predicted growth) or trailing, and either a one- to five-year time span. Check with the source providing the PEG ratio to see what kind of number they use.

Looking at the value of PEG of companies is similar to looking at the P/E ratio: A lower PEG means the stock is more undervalued.

Comparative Value
Let's demonstrate the PEG ratio with an example. Say you are interested in buying stock in one of two companies. The first is a networking company with 20% annual growth in net income and a P/E ratio of 50. The second company is in the beer brewing business. It has lower earnings growth at 10% and its P/E ratio is also relatively low at 15. (There are many other common ratios to use when comparing stocks, such as the P/S ratio. Learn more in How To Use Price-To-Sales Ratios To Value Stock.)

Many investors justify the stock valuations of tech companies by relying on the assumption that these companies have enormous growth potential. Can we do the same in our example?

Networking Company:

  • P/E ratio (50) divided by the annual earnings growth rate (20) = PEG ratio of 2.5

Beer Company:

  • P/E ratio (15) divided by the annual earnings growth rate (10) = PEG ratio of 1.5

The PEG ratio shows us that, when compare to the beer company, the always-popular tech company doesn't have the growth rate to justify its higher P/E, and its stock price appears overvalued.

The Bottom Line
Subjecting the traditional P/E ratio to the impact of future earnings growth produces the more informative PEG ratio. The PEG ratio provides more insight about a stock's current valuation. By providing a forward-looking perspective, the PEG is a valuable evaluative tool for investors attempting to discern a stock's future prospects.

(Every investor wants an edge in predicting a company's future, but a company's earnings guidance statements may not be a reliable source. To learn more, read Can Earnings Guidance Predict The Future?)

Related Articles
  1. Mutual Funds & ETFs

    4 Mutual Funds Warren Buffet Would Buy

    Learn about four mutual funds Warren Buffett would invest and recommend to his trustee, and discover detailed analysis of these mutual funds.
  2. Stock Analysis

    Markets Are Tanking: Time to Buy Like Buffett

    Learn about three value stocks Warren Buffett holds in his portfolio. See how Buffett uses market declines to find good deals on stocks.
  3. Stock Analysis

    4 Quick Service Restaurants for Your Portfolio

    Learn about the four quick service restaurants with attractive investment theses and growth prospects that can be valuable additions to your portfolio.
  4. Investing News

    4 Value Stocks Worth Your Immediate Attention

    Here are four stocks that offer good value and will likely outperform the majority of stocks throughout the broader market over the next several years.
  5. Mutual Funds & ETFs

    The 4 Best Buy-and-Hold ETFs

    Explore detailed analyses of the top buy-and-hold exchange traded funds, and learn about their characteristics, statistics and suitability.
  6. Stock Analysis

    The Biggest Risks of Investing in Netflix Stock

    Examine the current state of Netflix Inc., and learn about three of the major fundamental risks that the company is currently facing.
  7. Stock Analysis

    Investing in Lumber Liquidators? Read This First

    Find out what investors should know before buying Lumber Liquidators shares. Learn about Lumber Liquidators' financial performance and operational outlook.
  8. Stock Analysis

    What Seagate Gains by Acquiring Dot Hill Systems

    Examine the Seagate acquisition of Dot Hill Systems, and learn what Seagate is looking to gain by acquiring Dot Hill's software technology.
  9. Investing

    A Look at 6 Leading Female Value Investors

    In an industry still largely predominated by men, we look at 6 leading female value investors working today.
  10. Term

    What Is Financial Performance?

    Financial performance measures a firm’s ability to generate profits through the use of its assets.
  1. How do I read and analyze an income statement?

    The income statement, also known as the profit and loss (P&L) statement, is the financial statement that depicts the ... Read Full Answer >>
  2. Can working capital be too high?

    A company's working capital ratio can be too high in the sense that an excessively high ratio is generally considered an ... Read Full Answer >>
  3. How do I use discounted cash flow (DCF) to value stock?

    Discounted cash flow (DCF) analysis can be a very helpful tool for analysts and investors in equity valuation. It provides ... Read Full Answer >>
  4. What is the formula for calculating compound annual growth rate (CAGR) in Excel?

    The compound annual growth rate, or CAGR for short, measures the return on an investment over a certain period of time. Below ... Read Full Answer >>
  5. When does the fixed charge coverage ratio suggest that a company should stop borrowing ...

    Since the fixed charge coverage ratio indicates the number of times a company is capable of making its fixed charge payments ... Read Full Answer >>
  6. What is the difference between the return on total assets and an interest rate?

    Return on total assets (ROTA) represents one of the profitability metrics. It is calculated by taking a company's earnings ... Read Full Answer >>

You May Also Like

Hot Definitions
  1. Real Estate Investment Trust - REIT

    A REIT is a type of security that invests in real estate through property or mortgages and often trades on major exchanges ...
  2. Section 1231 Property

    A tax term relating to depreciable business property that has been held for over a year. Section 1231 property includes buildings, ...
  3. Term Deposit

    A deposit held at a financial institution that has a fixed term, and guarantees return of principal.
  4. Zero-Sum Game

    A situation in which one person’s gain is equivalent to another’s loss, so that the net change in wealth or benefit is zero. ...
  5. Capitalization Rate

    The rate of return on a real estate investment property based on the income that the property is expected to generate.
  6. Gross Profit

    A company's total revenue (equivalent to total sales) minus the cost of goods sold. Gross profit is the profit a company ...
Trading Center
You are using adblocking software

Want access to all of Investopedia? Add us to your “whitelist”
so you'll never miss a feature!