Master the most important stock valuation metric
In the world of investing, the Price-to-Earnings (P/E) Ratio is the metric everyone looks at first. It's kind of like a height or a bio on a dating app. It's a quick, shorthand way to see if a stock is a "catch" or if it's just trying to look better in its photos.
But here's the secret: a high P/E doesn't always mean a stock is expensive, and a low P/E doesn't always mean it's a bargain. If you don't know the context, you're essentially judging a flyweight and a heavyweight boxer by the same weight class.
At its simplest, the P/E ratio tells you how much you are paying for £1 of the company's profit.
Imagine you are buying a car wash for £100,000 which makes £10,000 profit a year.
When people ask "what is a good P/E ratio," they often confuse two different numbers:
This uses the actual profits a company made over the last 12 months. It's objective, but it's like looking in the rearview mirror while driving.
This uses estimated earnings for the next 12 months. This is what Wall Street actually cares about. As of January 2026, the S&P 500 forward P/E is roughly 22.4x, while the trailing P/E sits higher at 31.3x.
Why the gap? If a company's profits are expected to grow, the Forward P/E will be lower than the Trailing P/E. If you see a Forward P/E that is much higher, you want to understand why earnings are expected to drop. These numbers are also not baked in, so any revenue misses often hit the stock price as it changes the assumptions.
A company's P/E is heavily dictated by its "life stage." Comparing a young tech startup to an old utility company is like comparing a footballer who is just getting their first chances in the first team to someone who is a senior member of the squad: one is erratic but has "potential," the other is much more consistent but you know they have likely reached the ceiling on their potential.
Young but high ceiling — Milos Kerkez (left) cost £40 million in summer 2025, but Andy Robertson (right) has won it all and is Mr Consistent for Liverpool
(e.g., Early Amazon or Nvidia)
These companies often have astronomical P/E ratios, at best (think 50, 100+). More likely they will have a negative or not applicable P/E ratio as they won't yet be profitable.
Why? Investors aren't paying for what the company earned last year; they are paying for what they think it will earn in the next five years. If a company is doubling its earnings every year, a high P/E today will look like a steal tomorrow. For example, a company whose profits are doubling each year will see its P/E ratio half each year if everything else stayed the same.
(e.g., Coca-Cola or Johnson & Johnson)
These are mature companies. They aren't going to take over the world (they often already did), but they are reliable.
Why? You aren't expecting a moonshot. You're paying for stability and dividends. These companies do sometimes also have large P/E ratios, but it is incumbent upon their moat and the strength of it. A good example of this are the card payment networks, Visa and Mastercard. Their P/E ratios are frequently between 30-35. You might think that sounds risky, but they have a very large and well respected moat and an inflation proof business model that enables them to continue to grow double digits every year.
If you see a bank trading at a 15 P/E and a semiconductor company at a 45 P/E, the bank isn't necessarily "cheaper." Different industries have different "gravity."
| Sector / Index | Typical P/E Range | Why? |
|---|---|---|
| S&P 500 (US market) | ~22–25 (fwd) | Tech-heavy US index; higher growth expectations. |
| FTSE 100 (UK market) | ~11–14 (fwd) | Tilted toward banks, energy, and consumer staples — slower growth, higher dividends. |
| Semiconductor Equipment | ~40–50 | High growth, AI demand, massive future potential. |
| Software (SaaS) | ~30–40 | High margins, low capex repeatable model and recurring revenue. |
| Consumer Retail | ~18–25 | Steady demand but competitive; wide range depending on brand strength. |
| Energy (Oil & Gas) | ~8–15 | Highly cyclical, tied to commodity prices. Earnings swing year to year. |
| Regional Banks | ~10–15 | Highly regulated, slower growth, tied to interest rates. |
| Auto Manufacturers | ~6–10 | Massive capital costs, cyclical, and low profit margins. |
| Utilities | ~14–18 | Regulated, predictable earnings. Investors pay for stability, not growth. |
Notice the gap between the S&P 500 and FTSE 100? The US market trades at roughly double the P/E of the UK market. This doesn't mean US stocks are "overpriced" or UK stocks are "cheap" — the S&P 500 is dominated by high-growth tech companies, while the FTSE 100 is weighted toward mature banks, oil majors, and consumer staples that grow more slowly but pay higher dividends.
This is the most searched question about P/E ratios — and the honest answer is: it depends. There is no single "good" number that works for every stock. But there is a reliable process you can follow to decide whether a P/E ratio makes sense.
Use the table above as a starting point. A tech company at 30x might be fairly valued while a bank at 30x would be extremely expensive. Always compare like for like.
Look at the company's 5-year average P/E. If a stock usually trades at 20x and it's now at 35x, ask why. Has something fundamentally changed (new product, AI pivot, market expansion) — or is the market just getting excited?
Divide the P/E by the expected annual earnings growth rate. A PEG below 1.0 suggests you're getting growth at a reasonable price. A PEG above 2.0 suggests you're overpaying for that growth. Peter Lynch, one of the greatest fund managers ever, popularised this approach — if you want to go deeper, his book One Up on Wall Street is a must-read.
Watch out for "value traps." A very low P/E (say 4x or 5x) often means the market expects earnings to fall — the company might be in decline, losing market share, or facing regulatory problems. A low P/E is not automatically a bargain. Always ask: why is it cheap?
You'll often hear pundits scream that the market is at All-Time Highs (ATHs) and that P/E ratios are "higher than they were in the 80s," suggesting a crash is imminent. But comparing a 2026 P/E ratio to a 1980 P/E ratio is an apples-to-oranges comparison because the accounting rules have changed. Whilst current P/E ratios of the market are certainly not low at 31.3 vs. the long-term average of 19.4, this does not tell the full story.
In 1980, companies like Ford or GE built tangible things (factories, steel). These were "capitalized" - spread out over years on the balance sheet.
Today, companies like Google or Apple spend billions on intangible things (R&D, software code, brand building). Under current accounting rules, much of this is expensed immediately.
Modern companies look "less profitable" on paper than they actually are because they "spent" all their money on R&D today.
The P/E Trap: Because reported earnings (the "E") are artificially suppressed by these conservative rules, the P/E ratio (the "Price" divided by "E") looks artificially high.
Note: A P/E of 25 today might actually be "cheaper" than a P/E of 15 in 1980 because today's companies are more capital-light and have higher "hidden" asset values. No doubt things will continue to shift, but it again makes an important point not to just use averages when thinking about the P/E ratio.
The Bottom Line: The P/E ratio is a great conversation starter, but it's a terrible conclusion. Use it to ask why a stock is priced that way, rather than assuming the price is "wrong."
A P/E of 5 could mean a bargain, or it could mean the company is a "Value Trap" headed for bankruptcy.
Compare a bank to other banks, not to a software giant.
Is the earnings number high because of a one-time building sale? Or low because they spent a fortune on a new AI lab?
There is no single magic number. Compare the P/E to (1) the sector average, (2) the company's own 5-year average, and (3) the growth rate using the PEG ratio. See our three-step sanity check above for the full process.
Yes. If a company reports a net loss instead of a profit, the P/E is negative (or simply listed as "N/A"). This is common for young growth companies spending heavily to capture market share.
High P/E stocks are more volatile. Because the price is based on high expectations, any slight miss in earnings or negative news can cause the stock price to drop significantly as the "multiple" contracts. This can also happen as a company transitions between being a young high growth scale up to a mature company, resulting in a re-pricing and a lower multiple.
Simply take the current share price and divide it by the Earnings Per Share (EPS) found in the company's latest quarterly or annual report.
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