P/E Ratio

Stock trading dictionary: meaning, example and how traders use it.

Last updated: October 17, 2026

Definition: The P/E ratio (price-to-earnings ratio) is a valuation measure calculated by dividing a stock's share price by its earnings per share, showing how many dollars investors pay for each dollar of a company's annual profit.

P/E ratio formula

P/E ratio = Share price / Earnings per share (EPS)

EPS comes from the income statement: net income available to common shareholders divided by the weighted average number of shares. The same ratio can be computed at the company level as market capitalization divided by total net income.

  • Trailing P/E uses actual earnings over the past 12 months.
  • Forward P/E uses analysts' estimates for the next 12 months or fiscal year, so it depends on forecasts that may be wrong.

Example of a P/E calculation

Suppose Company A trades at $60 and earned $3.00 per share over the past year, so its trailing P/E is 20. Company B trades at $30 with EPS of $3.00, a P/E of 10. Both earn the same profit per share, but investors pay twice as much for each dollar of A's earnings.

That gap might be justified if A is expected to grow much faster. Suppose A's earnings are expected to rise to $4.50 next year; its forward P/E is $60 / $4.50 = 13.3. If B's earnings are expected to fall to $2.50, its forward P/E is 12. The valuations now look much closer than the trailing figures suggested.

How investors use the P/E ratio

The P/E ratio is a starting point in fundamental analysis. Investors compare it with:

  • The company's own history, to see whether it looks expensive relative to its past
  • Peers in the same stock sector, since typical multiples vary widely by industry
  • A broad market index, to gauge relative valuation

A high P/E often reflects expectations of strong growth, while a low P/E may indicate slower growth, higher risk, or a temporary setback. The PEG ratio, P/E divided by expected growth rate, attempts to adjust for growth differences. The earnings yield, EPS divided by price, is the inverse of P/E and can be compared with bond yields.

Limitations of the P/E ratio

P/E is meaningless when earnings are negative and can be misleading when earnings are temporarily depressed or inflated by one-time gains. Accounting choices and share buybacks affect EPS. Cyclical companies often show low P/Es at the peak of their earnings cycle, just before profits fall, and high P/Es near the bottom. The ratio also ignores debt; enterprise value multiples can be better for comparing companies with very different balance sheets. For these reasons, P/E works best alongside cash flow, growth, and balance sheet analysis rather than as a stand-alone signal.

Frequently asked questions

What is a good P/E ratio?

There is no single good level. It depends on growth prospects, risk, interest rates, and industry norms, so compare a stock with its peers and history.

What does a negative P/E ratio mean?

It means the company lost money over the period. Most data providers show the P/E as not applicable rather than as a negative number.

What is the difference between trailing and forward P/E?

Trailing P/E uses actual earnings from the past 12 months, while forward P/E uses estimated earnings for the coming year.

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For information only, not investment advice. See the disclaimer.