Price/earnings ratio (P/E ratio)

The price/earnings ratio compares a listed company’s share price with its earnings per share. It is a compact valuation multiple: it shows how much the market currently pays for a unit of reported or forecast earnings. It can support peer and historical comparison, but it cannot establish whether a share is attractive or a takeover is likely on its own.

When to use it

• Answer the performance question: “How does the market value this company relative to its earnings?”
• Assess the measure within the financial perspective.
• Compare businesses only after aligning earnings definitions, periods, capital structures and industries.
• Use it with growth, risk, cash flow, balance-sheet quality and accounting analysis—not as investment advice.

Origins

The P/E ratio has no clearly documented single inventor. It emerged from securities analysis as investors began expressing price relative to company earnings and became one of the most widely reported equity-valuation multiples. Regulators and investor-education services define the basic ratio as current share price divided by earnings per share, while market practice has developed trailing, forward and adjusted variants.

What it is

Perspective: Financial perspective.

Key performance question: How does the current share price compare with the company’s earnings?

A trailing P/E commonly uses recent reported earnings; a forward P/E uses forecast earnings. A ratio of price to $1 of earnings describes a market multiple, not a guaranteed payback period. Earnings are neither cash distributed to the investor nor necessarily sustainable, and the share price can change immediately.

A high ratio may reflect expected growth, durable returns, lower perceived risk, accounting differences or overvaluation. A low ratio may reflect weaker prospects, higher risk, cyclical peak earnings, distress or undervaluation. Interpretation requires a causal investment thesis and consistent data.

How to use it

Measurement

Choose the numerator date and denominator definition. State whether EPS is basic or diluted, trailing or forward, reported or adjusted, and whether extraordinary or non-recurring items are included. Check stock splits, buybacks, discontinued operations and fiscal-period alignment.