What Is the Price-to-Earnings (P/E) Ratio?
The P/E ratio measures how much the market is willing to pay for a dollar of a company's earnings. It is calculated as share price divided by earnings per share, or at the company level as equity value divided by net income, and the two forms give the same answer.
Because net income sits below interest expense, P/E is an equity-level multiple: it reflects value to shareholders after debt holders have been paid. That makes it sensitive to leverage, which is both a feature and a limitation compared with enterprise value multiples.
How It Works
P/E can be quoted on trailing earnings (the last twelve months) or forward earnings (the next year's consensus estimate), and forward P/E is usually lower for growing companies. Higher multiples generally signal expectations of faster earnings growth, higher returns on capital, or lower risk, while low multiples can indicate either a bargain or a business in decline.
Analysts compare a company's P/E against sector peers, the broader market such as the S&P 500, and the company's own historical range. One-time gains or charges can distort reported EPS, so practitioners often use normalized or adjusted earnings.
Example
A stock trades at $60 and earned $3.00 of EPS over the last twelve months, so its trailing P/E is $60 / $3.00 = 20.0x. If consensus expects EPS of $4.00 next year, the forward P/E is $60 / $4.00 = 15.0x.
If comparable companies trade at 18.0x forward earnings, applying that multiple implies a value of 18.0 x $4.00 = $72 per share, about 20% above the current price. Interviewers commonly ask why two companies with identical earnings can deserve different P/E ratios, and growth, risk, and capital structure are the core of the answer.
Why It Matters
P/E is the most widely quoted valuation metric in equity markets and drives merger math too, since accretion and dilution in a stock deal depend on the relative P/E ratios of buyer and seller. It is intuitive and quick, which is why earnings headlines and price targets so often reference it.
Its weaknesses are meaningful, though: it is useless for unprofitable companies, distorted by leverage and one-time items, and blind to differences in growth, which is exactly the gap the PEG ratio tries to fill.
