Price-to-Earnings Multiple
The price-to-earnings (P/E) ratio is the price an investor pays for each dollar of a company’s earnings, an equity-level multiple equal to price per share over earnings per share (EPS). A P/E of 15 means the market charges A$15 for A$1 of annual profit. It can be computed on trailing earnings, the last twelve months actually reported, or on forward earnings, the analyst forecast for the year ahead. For a stable-growth firm the constant-growth model shows the justified P/E rises with the growth rate and falls with the required return , so a high P/E often signals strong expected growth rather than a simply expensive stock. Because EPS is an accounting figure, the ratio inherits the limits of accrual earnings.
Try it yourself
Value a company off comparable peers. Take the medianpeer multiple and apply it to the target's own fundamental. EV multiples give an enterprise value, so you bridge to equity by subtracting net debt. Equity multiples (P/E, P/S) give the share price directly.
Cheap vs rich peers move the implied value a long way — the multiple imports the peer set's pricing. Then flip to P/E: an equity multiple lands on price directly, with no net-debt bridge.
Match the numerator to the denominator. EV/EBITDA is capital-structure-neutral, so an enterprise-value numerator must sit over a pre-interest measure such as EBITDA. Never pair EV with net income, which is already after interest. P/E and P/S are equity multiples and land on the share price directly.
Reflect: the median resists a single rich or distressed peer that would drag the mean. But every multiple inherits whatever mispricing sits in the comp set. When would you trust a multiple over a full discounted-cash-flow valuation, and when not?
Why it matters
P/E answers a plain question. How many years of current earnings am I paying for this share? Pay A$30 for a stock that earns A$2 and you are on a P/E of 15. The reason a fast grower trades richer is that you are buying tomorrow’s larger earnings, not just today’s. Forward P/E makes that explicit by using next year’s expected EPS, which is usually higher, so the forward number typically sits below the trailing one. The catch is that earnings can be soft. A loss makes the ratio meaningless, and aggressive accounting can flatter EPS and distort comparisons.
Formulas
Worked examples
Company A trades at A$30 with EPS of A$2. The industry average P/E is 20. Is the stock cheap or dear on this multiple, and what would justify the gap?
The stock’s P/E is A$30 over A$2, which is 15, below the peer average of 20. On this single multiple it looks cheap relative to peers, by about a quarter. Before calling it a bargain, ask what the constant-growth lens implies. A lower justified P/E is consistent with slower expected growth or higher risk for Company A. If its growth and risk truly match the peers, the discount is hard to justify and the stock looks undervalued. If the market simply expects it to grow more slowly, the lower multiple is fair.
Common mistakes
- ✗A low P/E always means a cheap stock. A low multiple can be a value trap where the market correctly expects earnings to fall. Cheapness needs the low multiple to be unjustified by fundamentals.
- ✗A high P/E always means an overpriced stock. A high P/E often reflects strong expected growth or low risk, which the justified-P/E formula prices in directly.
- ✗The P/E ratio works whatever the earnings. With negative EPS the ratio has no economic meaning, since a negative denominator cannot be read as a years-of-earnings price.
- ✗Trailing and forward P/E are interchangeable. Trailing uses past reported earnings while forward uses forecasts, so they can diverge sharply when earnings are expected to change.
Revision bullets
- •P/E is price per share divided by earnings per share
- •It is the price paid for each dollar of annual earnings
- •Trailing P/E uses past EPS, forward P/E uses forecast EPS
- •Justified P/E rises with growth and falls with the required return
- •A high P/E often signals growth, not simply an expensive price
- •Negative or accrual-heavy earnings make the ratio unreliable
Quick check
A stock priced at A$45 has earnings per share of A$3. Its price-to-earnings ratio is
Holding the payout ratio fixed, the justified price-to-earnings ratio of a stable-growth firm rises when
Connected topics
Sources
- Titman & Martin, Ch. 8Titman, S., & Martin, J. D. Valuation: The Art and Science of Corporate Investment Decisions. Pearson.Derives the P/E multiple, the stable-growth justified P/E and the trailing-versus-forward distinction.
- Sloan (1996), TARSloan, R. G. "Do Stock Prices Fully Reflect Information in Accruals and Cash Flows about Future Earnings?" The Accounting Review, 71(3), 1996, pp. 289-315.Cash-based earnings predict future earnings better than accruals, which bears on the quality of the EPS in a P/E.