P/E Ratio Explained: How to Tell If a Stock Is Cheap or Expensive (With Examples)
Updated October 2026 · 11 min read Is a $500 stock expensive? Is a $15 stock cheap? Most beginners judge a stock by its share price, but the price alone tells you almost nothing. A $500 stock can be a bargain, and a $15 stock can be wildly overpriced. What matters is how much you pay compared with what the company actually earns. The most widely used tool for measuring that is the price-to-earnings ratio , or P/E ratio . You'll see it on every stock quote page, in every earnings story, and in almost every conversation about whether the market is "too high." This guide explains what the P/E ratio means, how to calculate it, how to use it to compare stocks, and the traps that catch investors who rely on it alone. Key takeaways The P/E ratio shows how many dollars investors pay for each $1 of a company's yearly earnings. Trailing P/E uses the past 12 months of earnings; forward P/E uses analysts' estimates for the next 12 months. As of early October 2026...