The price-to-earnings ratio (P/E ratio) is one of the first numbers investors look at when evaluating a stock. It tells you how much you're paying for every dollar of a company's earnings.
The Simple Formula
P/E Ratio = Stock Price / Earnings Per Share (EPS)
If a stock trades at $100 and the company earned $5 per share last year, the P/E ratio is 20. That means investors are paying $20 for every $1 of earnings.
Why It Matters
The P/E ratio gives you a quick sense of whether a stock is expensive or cheap relative to what the company actually earns. A stock trading at $500 isn't necessarily "expensive" if the company earns $50 per share (P/E of 10). And a $10 stock isn't "cheap" if earnings are only $0.10 per share (P/E of 100).
Think of it like buying a rental property. You wouldn't just look at the purchase price. You'd compare it to the annual rent you'd collect. The P/E ratio does the same thing for stocks.
What's a "Good" P/E?
There's no single answer because it depends on the industry and growth expectations.
Low P/E (under 15): Often found in mature, slow-growth companies. Johnson & Johnson (JNJ) typically trades with a lower P/E because it's a stable healthcare company that grows steadily but not explosively. A low P/E can mean a stock is undervalued, or it can mean the market expects earnings to decline.
Medium P/E (15 to 25): This is roughly the historical average for the S&P 500. Apple (AAPL) often trades in this range. It reflects a company with solid earnings and moderate growth expectations.
High P/E (above 30): Common for fast-growing companies. NVIDIA (NVDA) has traded at high P/E ratios because investors expect its earnings to grow rapidly. You're paying a premium today for expected future growth.
Two Types of P/E
Trailing P/E uses the last 12 months of actual earnings. This is backward-looking but based on real numbers.
Forward P/E uses analyst estimates for the next 12 months of earnings. This is forward-looking but based on predictions that could be wrong.
Most stock pages (including ConvictionStocks) show both so you can compare.
Common Mistakes
Comparing P/E across industries. A tech company with a P/E of 30 isn't necessarily more expensive than a utility company with a P/E of 12. Different industries have different normal ranges.
Ignoring negative earnings. If a company is losing money, the P/E ratio doesn't work. You'll see "N/A" instead of a number. This doesn't mean the stock is worthless. It means you need other metrics.
Using P/E alone. The P/E ratio is one piece of the puzzle. A low P/E might signal a value opportunity, or it might signal a company in trouble. Always look at the full picture: revenue growth, debt levels, competitive position, and what's driving the numbers.
The Bottom Line
The P/E ratio is a starting point, not a final answer. It helps you quickly gauge market expectations for a company. High P/E means investors expect strong future growth. Low P/E means they expect slower growth or see higher risk.
Use it as a screening tool to find stocks worth researching further, then dig into the details to understand the full story.
This content is for informational purposes only and does not constitute financial advice.