You’ll see the P/E ratio on every stock page, every finance app, every analyst report. It’s probably the most quoted number in all of investing. And most beginners either ignore it completely or misunderstand what it actually tells them.
Let me fix that in about 5 minutes.
P/E Ratio — The Dead Simple Explanation
P/E stands for Price-to-Earnings. The formula is:
P/E = Stock Price ÷ Earnings Per Share
That’s it. If a stock costs $100 and the company earned $5 per share last year, the P/E is 20. Translation: investors are paying $20 for every $1 of profit the company makes.
Think about it in real-world terms. Would you buy a small business that makes $50,000 a year for $500,000? That’s a P/E of 10 — most people would say that’s a fair deal. Would you pay $2 million for that same business? That’s a P/E of 40 — you’d need a very good reason to pay that much.
Stocks work the exact same way. You can see the P/E for every S&P 500 company on our stock directory, and our screener lets you filter by P/E range to find cheap or expensive stocks.
What’s a “Good” P/E Ratio?
This is where most guides give you a wishy-washy “it depends.” And yeah, it does depend, but here are actual numbers you can work with:
- Under 15: Cheap territory. The market thinks this company’s growth is slow, or there’s some risk. Banks like Bank of America and telecoms like Verizon live here. Sometimes these are bargains. Sometimes they’re cheap for a reason.
- 15-25: Fair value for a solid, growing company. This is where the bulk of the S&P 500 sits. Think Procter & Gamble, Coca-Cola, Johnson & Johnson.
- 25-40: Growth premium. You’re paying extra because the market expects above-average earnings growth. Apple and Microsoft typically trade here.
- Above 40: High-growth or speculative. The market is pricing in massive future earnings that haven’t materialized yet. NVIDIA and Tesla have spent time in this range.
The S&P 500’s average P/E has historically hovered around 20-25. Check the current market average on our market overview page.
The One Rule That Changes Everything
Here it is: never compare P/E ratios across different sectors.
A tech company with a P/E of 35 might be undervalued. A utility company with a P/E of 35 is almost certainly overvalued. Why? Because tech companies grow earnings at 15-25% per year, while utilities grow at 3-5%. The faster a company grows, the higher P/E investors are willing to pay.
Always compare apples to apples. Use our stock comparison tool to put 2-4 stocks from the same sector side by side. If one tech stock has a P/E of 25 and another similar one has a P/E of 40, that’s a meaningful difference worth investigating.
Trailing vs Forward P/E — Which One Matters?
Trailing P/E
Uses the last 12 months of actual, reported earnings. This is the number you see on most financial sites, including our stock pages. The advantage: it’s based on real data, not guesses. The downside: it’s backward-looking.
Forward P/E
Uses Wall Street analyst estimates for the next 12 months of expected earnings. The advantage: it accounts for expected growth. The downside: analysts are wrong all the time. Forward P/E is useful but don’t treat it as gospel.
For most investors, trailing P/E is the safer metric to rely on. We show trailing P/E across our platform.
3 Common P/E Traps to Avoid
Trap 1: “Low P/E Means Buy”
A P/E of 8 looks like a screaming bargain until you find out the company’s earnings are shrinking 20% per year. That low P/E is actually going to get higher as earnings drop — even if the stock price doesn’t move. This is called a value trap, and it catches beginners constantly. Always check WHY a P/E is low before getting excited.
Trap 2: “High P/E Means Avoid”
Amazon traded at a P/E above 100 for years. People said it was absurdly expensive. Those who bought anyway and held are up 1,000%+. A high P/E is justified when earnings are growing fast enough to bring it down over time. NVIDIA’s P/E has actually been dropping even as the stock rises — because earnings are growing faster than the price.
Trap 3: Ignoring Negative P/E
If a company loses money, its earnings are negative, so the P/E ratio is meaningless (or shown as “N/A”). This doesn’t automatically mean avoid it — some great growth companies are unprofitable early on. But it does mean P/E isn’t the right tool for evaluating them. Look at revenue growth and cash burn instead.
How to Actually Use P/E When Picking Stocks
Here’s a practical workflow that takes about 5 minutes:
- Go to the stock screener and pick a sector you’re interested in
- Sort by P/E ratio, lowest to highest
- Identify 3-5 stocks with lower P/Es than their peers
- Use the comparison tool to check if they’re cheap for good reasons (steady business, solid dividend) or bad reasons (declining revenue, management problems)
- Check the dividend yield too — a low P/E stock with a strong dividend is a classic value play. Run the numbers on our dividend calculator
P/E is a starting point, not a finish line. Use it to identify candidates, then dig deeper into the full picture.
Frequently Asked Questions
What P/E ratio does Warren Buffett look for?
Buffett doesn’t have a magic number. He famously said he’d rather buy “a wonderful company at a fair price than a fair company at a wonderful price.” In practice, most of his holdings trade between 15-30x earnings. Check what he owns in our Buffett’s Picks collection.
Can a stock have no P/E ratio?
Yes. If the company has zero or negative earnings, the P/E is undefined. You’ll see “N/A” or “—” on our stock pages for these companies. It doesn’t mean the stock is bad — it means you need a different metric to evaluate it.
Is P/E the most important metric?
It’s the most popular, but not the only one. Dividend yield, price-to-sales, debt levels, and revenue growth all matter too. P/E is a great first filter — but never the only thing you should look at. Our screener lets you filter by multiple metrics at once.
Why do tech stocks have higher P/E ratios?
Because they grow faster. A company growing earnings 25% per year will have a high P/E today, but that P/E comes down quickly as earnings catch up. Investors are willing to pay a premium for that growth. Slower-growth sectors like utilities and banks have lower P/Es because their earnings growth is more modest.
Should I only buy stocks with low P/E ratios?
No. A portfolio of only low-P/E stocks would be heavily concentrated in banks, energy, and telecoms — not exactly a recipe for exciting growth. Balance is key. Mix some value (low P/E) stocks with growth (higher P/E) stocks. Take our risk assessment quiz to figure out what balance works for your goals.