What it means
A P/E of 15 means that investors pay $15 for every $1 of profit the company earns in a year. It is a quick way to compare how the market values different businesses of different sizes.
A high ratio usually means investors expect strong growth, while a low one may mean slow growth, high risk or a market that is cautious. There are two common versions.
The trailing P/E uses the profit from the last twelve months, which is a known figure. The forward P/E uses forecast profit for the coming year, which is more useful for judging the future but depends on someone's estimate.
The ratio is helpful because it is simple and almost every listed company has one. Managers use it to see how the market values their own business compared with competitors, and it shapes how they think about share issues, takeovers and employee share plans.
Investors use it as a first screen for finding companies that look cheap or expensive. It has weaknesses.
A company with no profit has no meaningful P/E, a one-off gain or loss can distort earnings, and different accounting choices can make profits hard to compare. It also ignores debt, so two companies with the same P/E can carry very different financial risk.
For these reasons, the P/E is best read alongside growth rates, debt levels and cash flow. Compare it with the same company's own history and with firms in the same sector, because average ratios differ greatly between industries.
Managers should know what drives their own multiple. Consistent profit, low debt, clear communication and visible growth plans tend to support a higher ratio, while surprises, restatements and heavy reliance on a few customers tend to lower it.
Improving those areas can raise the value investors place on every dollar of profit.
In practice
Real-world examples.
Example
An investor compares two supermarket chains. One trades on a P/E of 11 and the other on 18, and she researches why the market is paying more for the second, finding that it is growing faster.
Example
A founder preparing to sell her software business looks at the P/E ratios of listed competitors to estimate a sensible asking price. She applies a discount because her company is private and smaller.
Example
A chief executive in the energy industry sees her share price fall while profit rises, so the P/E shrinks. She uses the investor call to explain why the earnings are sustainable and not a temporary peak.
Formula
Calculation
Price-earnings ratio = Share price / Earnings per share, where Earnings per share = Net profit / Number of shares in issue.
A company has net profit of $60,000,000 and 20,000,000 shares in issue. Earnings per share are $60,000,000 / 20,000,000 = $3.00. The shares trade at $45, so the trailing P/E is $45 / $3.00 = 15.
If analysts forecast earnings per share of $3.60 next year, the forward P/E is $45 / $3.60 = 12.5. The forward figure is lower because profit is expected to grow, so the same price buys more future earnings. If the share price rose to $54 on the same $3.00 of trailing earnings, the trailing P/E would increase to $54 / $3.00 = 18, which shows that the ratio can rise purely because investors become more optimistic.Case study
Seen in the real world.
Oakridge Building Supplies is a fictional distributor of construction materials. In an illustrative scenario, its shares traded at $30 with earnings per share of $2.50, giving a P/E of 12, while the sector average was 16.
The finance director wanted to know whether the gap reflected a real weakness or a market misunderstanding. She found that analysts were worried about the company's reliance on a single large customer, not about its profit.
The fictional company then signed three new customer contracts and published a clearer breakdown of revenue. Over the next year the P/E moved up toward 15, showing how a ratio can change because of perceived risk even when profit is unchanged.
Watch out
Common mistakes.
- Assuming a low P/E always means a bargain, when it may signal a business with falling profit.
- Comparing P/E ratios across very different industries, which have different growth and risk profiles.
- Using the ratio when earnings include large one-off items, which can badly distort the result.
Questions
People also ask.
What is a good P/E ratio?
There is no universal answer, because it depends on the industry, growth and interest rates, so compare it with similar companies and the firm's own history.
What is the difference between trailing and forward P/E?
Trailing uses profit already earned, while forward uses forecast profit for the next period.
What does a negative P/E mean?
The company made a loss, so the ratio is not meaningful and is usually shown as not applicable.
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