P/E Ratio (Price-to-Earnings): What It Is

What is the P/E ratio?

The P/E ratio is one of the most widely used measures for valuing a stock. It compares a company's share price with the profit attributable to each share, and the result is read as a multiple: for a stock with a P/E of 20, investors are paying 20 times one year of the company's earnings per share.

The SEC's investor glossary defines it the same way: the ratio of a company's share price to its earnings per share. The company-wide version of the same calculation is market cap divided by annual net income; both routes give the same answer.

Formula and worked example

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

Earnings per share is the period's net profit attributable to ordinary shareholders divided by the weighted average number of shares. Under international reporting standards the rules sit in IAS 33; in the US, in ASC 260. Companies usually report two figures: basic EPS and diluted EPS, which also counts the effect of convertible instruments and options.

Example:

• Share price: 100
• Earnings per share over the last 12 months: 5
• P/E = 100 ÷ 5 = 20

The inverse of P/E is the earnings yield: 5 ÷ 100 = 5%. It is a rough way to compare a stock with other yields, such as bond interest.

Trailing vs forward P/E

• Trailing P/E uses the actual earnings of the last four quarters. It rests on reported numbers but looks backward.
• Forward P/E uses expected earnings for the next 12 months. It looks ahead but depends on estimates, so it moves as estimates change.

A fast-growing company usually has a lower forward P/E than trailing P/E because expected earnings are higher than current ones. Always check which version is being quoted.

How to read it

There is no agreed line where a P/E becomes "cheap" or "expensive". The ratio only means something in context:

• Sector: technology companies often trade on higher P/Es than banks or energy firms because of growth expectations. Comparing a software company's P/E with a bank's is misleading.
• Growth: a high P/E can signal that the market expects higher future profits. The PEG ratio, P/E divided by the expected annual earnings growth rate, tries to adjust for this.
• The company's own history: today's P/E can be compared with the company's long-run average.
• Interest rates: when rates are low, investors tend to accept higher P/Es.

A low P/E does not prove a stock is cheap; the market may expect earnings to fall. A high P/E does not prove it is expensive either.

Example: comparing two companies

The table below uses made-up example figures to show how two companies in the same sector might be compared:

On P/E alone, B trades at half A's valuation. Once growth is added, the picture flips: A's higher P/E may reflect faster expected growth, while B's low P/E may reflect slow growth. The comparison does not give an answer; it shows which questions to ask. Is the growth estimate realistic, are the earnings sustainable, how much debt is there?

For valuing whole markets over long periods, some analysts use the cyclically adjusted P/E (CAPE), which divides price by the average inflation-adjusted earnings of the past ten years to stop one unusually good or bad year from distorting the ratio.

Limits of the P/E ratio

• Negative earnings: a loss-making company has no meaningful P/E; most sources leave it blank or show "n/a".
• One-off items: an asset sale or a large write-down can inflate or depress earnings for a period.
• Cyclical companies: in commodity and industrial firms, earnings peak at the top of the cycle, so the P/E can look lowest exactly then.
• Accounting differences: profit rules vary between countries and companies.

That is why P/E is read together with other measures such as market cap, debt, cash flow and growth. On a price chart, support and resistance levels answer a different question, where price may react; P/E belongs to fundamental analysis.

Why crypto assets have no P/E

P/E is calculated for a share that gives its holder a claim on company profits. Cryptocurrencies such as bitcoin have no income statement and no earnings per share, so a classic P/E cannot be computed. Some analysts compare a protocol's fee revenue with its token value, but token holders often have no legal claim on that revenue. For a tokenized stock tracking a share, the relevant P/E is that of the underlying company.

ETFs can have a P/E too: fund providers compare the weighted earnings of the holdings with the fund's price.

Reading P/E on stock price pages

Seeing P/E next to the price puts a stock's valuation in context at a glance. For example, the NVIDIA (NVDA) stock price and P/E, Apple (AAPL) stock price and Microsoft (MSFT) stock price pages show price and basic valuation data together. What the companies do is covered in the NVIDIA and Apple entries; for the chart side, see NVIDIA technical analysis.

The P/E figure updates as new results are reported and as the price moves. The full list is at US stocks, ETFs and commodities prices, and earnings-season developments under TradFi news. The wider frame of traditional markets is in the TradFi entry.