Definition
The Price-to-Earnings ratio is calculated as market price per share divided by earnings per share (EPS). The 'trailing P/E' uses the last twelve months of earnings; the 'forward P/E' uses analyst estimates for the next twelve months. P/E is most meaningful when compared within an industry, since different sectors trade at structurally different multiples — mature utilities may trade at 12–15x earnings, while high-growth software firms often exceed 30–50x. A very high P/E can signal richly-priced growth expectations, while a very low P/E may indicate a value opportunity — or a company in distress. P/E is not usable for companies with negative earnings.
P/E = Market Price per Share / Earnings per Share (EPS)
Example
If AAPL trades at $200 and generated $6.50 in EPS over the last twelve months, its trailing P/E is 200 / 6.50 ≈ 30.8x. Meaning: investors pay about $30.80 for every $1 of current annual earnings.
Frequently Asked Questions
What is a good P/E ratio?
There is no universal answer — it depends on sector, growth stage, and interest-rate environment. As a rough benchmark: the long-term S&P 500 average is around 15–18x. Software may run 30–50x; utilities 12–18x.
What does a negative P/E mean?
It means the company reported a loss over the measurement period. Most quoting platforms display it as N/A rather than a negative number, since a negative P/E is not meaningful for valuation comparison.
Should I always buy low-P/E stocks?
Not automatically. Some companies trade at low P/E because the market anticipates declining earnings or business risk. Always investigate WHY the multiple is low before treating it as a bargain.