How to calculate P/E
P/E is the share price divided by earnings per share (EPS). EPS is the company's net profit divided by the number of shares outstanding.
For example, if a stock trades at $50 and the company earned $2.50 per share over the last year, its P/E is 50 ÷ 2.50 = 20. Investors are paying $20 for every $1 of annual profit.
Trailing vs. forward P/E
- Trailing P/E uses the last 12 months of reported earnings. It's based on real results, but it looks backward.
- Forward P/E uses analysts' estimates of next year's earnings. It looks ahead, but estimates can be wrong.
When a website shows a single P/E without saying which one, it's usually trailing.
What is a good P/E ratio?
There is no single good number. P/E only means something when you compare it: with the same company's history, with similar companies in its sector, or with the overall market. Fast-growing technology companies often trade at much higher P/Es than utilities or banks, because investors expect their profits to grow faster.
A low P/E can mean a bargain, or it can mean the market expects profits to fall. A high P/E can mean strong expected growth, or it can mean the stock is priced for perfection. P/E is a starting question, not an answer.
Limits of the P/E ratio
P/E doesn't work when a company has no profit: with zero or negative earnings the ratio is meaningless, which is why many sites show it as blank. One-off gains or charges can also distort a single year's earnings. And P/E says nothing about debt, cash or how fast the business is growing, so investors usually look at it alongside other measures.
P/E and insider buying
Some investors look for stocks where insiders are buying and the P/E is below the sector's typical level, on the idea that the people running the company think it's undervalued. InsiderPrint shows each stock's P/E next to its insider activity, and our sector pages show the median P/E for each sector so you can compare.