TL;DR The P/E ratio is a stock's price tag divided by its yearly profit — it tells you how many dollars you're paying for every $1 the company earns.
The plain-English version
P/E stands for price-to-earnings. Take the share price, divide it by the company's earnings per share over the last year, and you get one number.
If a stock trades at $100 and the company earned $5 per share this year, the P/E is 20. You're paying $20 for every $1 of annual profit.
Think of it like buying a lemonade stand. If the stand makes $1,000 a year in profit and the owner wants $20,000 for it, you're paying 20 times earnings — a P/E of 20. Same math, smaller lemonade.
What counts as high or low?
There's no universal "good" number, and anyone who gives you one is oversimplifying. Rough context:
- The S&P 500 has historically averaged somewhere in the teens to low twenties.
- Slow, steady businesses (utilities, banks) usually trade at lower P/Es.
- Fast-growing tech companies often trade at very high P/Es — investors are paying today for profits they expect years from now.
A high P/E means the market expects growth. A low P/E means the market expects little — or smells trouble.
The common mistake
Beginners treat a low P/E as "cheap, therefore good" and a high P/E as "expensive, therefore bad." Wrong both ways. A stock at a P/E of 6 might be a bargain — or a business the market believes is dying, which is why it's priced like a clearance rack. A P/E of 80 might be absurd — or reasonable for a company doubling its profit every year.
The P/E is a starting question, never an answer. It tells you what the market expects; your job is deciding whether the market is right.
Why you care
It's the most-quoted number in investing, and it turns any stock price into something comparable. $900 per share isn't "expensive" and $4 per share isn't "cheap" — the P/E is one way to actually compare them.
Educational only — not investment advice. The P/E can't tell you what to buy; it can only help you understand what you're looking at.