The price-to-earnings ratio, or P/E, is the first number most investors learn and the one they lean on longest. It's simple to calculate — share price divided by earnings per share — but "what counts as good" is where most people get stuck. A P/E of 15 looks cheap next to a P/E of 40, but cheap relative to what? The honest answer is that a good P/E ratio only exists in context: the market's current level, the company's sector, and its growth prospects.
What the P/E ratio actually measures
P/E tells you how many dollars investors are paying today for each dollar of a company's annual earnings. A stock trading at 20x earnings costs $20 for every $1 of profit the company generated over the past year (trailing P/E) or is expected to generate over the next year (forward P/E). A higher multiple means the market is pricing in faster growth, more durable profits, or both. A lower multiple usually means the opposite — slower growth, more risk, or both.
So what's "good" right now?
As of mid-August 2026, the S&P 500 is trading around 29-30x trailing earnings — well above its long-run historical average of roughly 16x going back to the late 1800s. That gap matters: a stock at 25x today isn't necessarily expensive, it may just be trading close to the broad market, while the same 25x multiple would have looked rich by historical standards a decade ago. Context also has to include sector. Technology stocks currently command some of the highest multiples in the market — often 40x forward earnings or more for the sector as a whole — because investors are paying up for growth. Energy and financial stocks, by contrast, tend to trade at some of the lowest multiples, often in the 13-16x range, reflecting slower growth and more cyclical earnings. Comparing a bank's P/E to a software company's P/E and calling one "better" misses the point; the useful comparison is a stock against its own sector and its own history.
Where P/E misleads you
P/E has three well-known blind spots. First, it says nothing about debt — two companies with identical P/E ratios can carry very different levels of financial risk, which is why pairing P/E with a metric like debt-to-equity gives a fuller picture. Second, earnings can be temporarily inflated or depressed by one-off items, making a single year's P/E misleading; looking at a multi-year trend helps. Third, unprofitable or early-stage companies have no meaningful P/E at all, since the ratio breaks down with zero or negative earnings — that's when metrics like price-to-sales become more useful. Used alone, a low P/E screen tends to catch as many "value traps" — cheap stocks that stay cheap because the business is deteriorating — as it does genuine bargains.
Compare a stock to its own history, not just the market
A company's own P/E range over the past five or ten years is often more informative than a market-wide benchmark. A retailer that has historically traded between 12x and 18x earnings and is currently sitting at 11x is arguably cheap on its own terms, even if the S&P 500 as a whole looks expensive at 29x-30x. Conversely, a stock trading at the low end of the market's range but at the high end of its own history isn't automatically a bargain. Multiples compress and expand with interest rates, sentiment, and the broader cycle, so a stock's P/E today should be read against where it has traded before, not treated as a fixed, universal yardstick.
PEG: adjusting P/E for growth
One popular fix for comparing companies with different growth rates is the PEG ratio — P/E divided by expected earnings growth rate. A stock trading at 30x earnings with 30% expected annual growth has a PEG of 1.0, while a stock at 15x earnings with only 5% growth has a PEG of 3.0. On a raw P/E basis the second stock looks cheaper; on a growth-adjusted basis, the first one is. PEG isn't perfect — it leans heavily on analyst growth estimates, which can be wrong — but it's a useful sanity check before assuming a high-multiple stock is automatically overpriced.
A more reliable way to screen for value
Rather than picking one "good" P/E number, it's more reliable to filter for a reasonable P/E range relative to the market and sector, then layer on quality checks — positive and stable earnings growth, manageable debt, and solid return on equity — so a low multiple reflects an overlooked stock rather than a business in decline. That combination does more work than P/E alone ever can.