How it works
The price-to-earnings ratio is the multiple the market places on each dollar of a company's earnings: $150 per share divided by $8.50 of EPS is a P/E of 17.6 — you pay $17.60 for every $1 of profit. The engine computes it in one division and leaves the interpretation to you, which is where the real skill lives. A P/E is only meaningful in context: versus the company's own history, versus its sector, and versus growth. A 40x P/E looks absurd until the company grows earnings 25% a year; a 8x P/E looks cheap until earnings decline. The two standard refinements are forward P/E (next year's expected EPS — lower, because markets price growth) and the PEG ratio (P/E divided by growth), which normalises for growth. The engine works with any EPS figure you enter, so trailing and forward versions are both one click away. Every field in this calculator exists for a reason. Enter Share price, Earnings per share, P/E ratio, Price, EPS, All inputs stay in your browser. Adjust one field at a time to see which lever moves the answer most — the formula on this page lets you verify every step against the defaults shown in the worked example.
Formula
P/E = Share price / Earnings per share
Tips
- Compare a stock's P/E to its sector average and its own 5-year range, not to the market as a whole.
- Forward P/E (using expected EPS) is the number analysts actually trade on.
- A P/E below the sector with similar growth is the classic value signal; above with similar growth, the classic warning.
- Negative-earnings companies have no meaningful P/E — use price-to-sales for those.
Frequently asked questions
- What is a good P/E ratio?
- It depends on the sector and growth. Mature utilities trade near 10-15x; fast-growing tech can justify 30x+; the S&P 500 historically averages 15-20x. The number only means something relative to growth (try the PEG ratio) and to the company's own history.
- What is the difference between trailing and forward P/E?
- Trailing P/E uses the last twelve months of actual earnings; forward P/E uses analysts' expected earnings for the next year. Forward is almost always lower, because markets expect growth — the gap between the two is the market's growth expectation in disguise.
- What is the PEG ratio?
- P/E divided by the expected earnings growth rate. A PEG near 1 is considered fair — the multiple and growth balance. A PEG well below 1 suggests undervaluation relative to growth; well above, the opposite. It is the P/E adjusted for the company's engine.
- Can a high P/E be justified?
- Yes, when growth is real and durable. The market pays multiples for compounding machines; the mistake is paying a growth multiple for a no-growth company. Compare P/E against the growth rate (PEG) and against the company's track record of delivering it.