What Is a P/E Ratio? How to Use It Without Getting Fooled

If you spend any time around stocks, you will hear people talk about the P/E ratio. It is one of the most quoted numbers in investing, and one of the most misused.

The basic idea

P/E stands for price-to-earnings. Take the share price and divide it by the company’s earnings per share over the past year. A stock at $50 that earned $2.50 per share has a P/E of 20. Put another way, you are paying $20 for every $1 of yearly profit.

High vs low

A high P/E usually means investors expect strong growth, so they will pay up today. A low P/E can mean the stock is cheap, or it can mean the market thinks the business is in trouble. The number alone does not tell you which.

Compare like with like

A P/E of 30 might be normal for a fast-growing software company and sky-high for a bank. Compare a stock with its own history and with similar companies, not with the whole market.

Trailing vs forward

• Trailing P/E uses earnings from the past 12 months.
• Forward P/E uses analyst estimates for the next 12 months, so it is only as good as the guesses behind it.

Where it can mislead you

• A company with no profit has no usable P/E.
• One-time gains or losses can distort earnings for a year.
• Cyclical companies, like miners or car makers, can look cheap at the top of their cycle, right before profits fall.

How to use it

Treat P/E as a starting question, not an answer. If a P/E looks very high or very low, ask why. Then look at growth, debt and cash flow before you decide anything.

Related reading

• Value vs Growth Stocks: What Is the Difference?
• How to Read an Earnings Report: The Numbers That Matter

This is general education, not financial advice.