What is this PER (P/E ratio) calculator?
A free, browser-based calculator for the price-to-earnings ratio (PER). Enter a share price and earnings per share (EPS) and it returns the PER along with the earnings yield (1 ÷ PER) and a rough payback period. The PER is one of the most widely used yardsticks for judging whether a stock looks cheap or expensive. Everything runs locally in your browser, so your numbers are never uploaded.
How PER is calculated
The PER is simply the share price divided by earnings per share: PER = price ÷ EPS. Its inverse is the earnings yield — EPS ÷ price, or 1 ÷ PER — which expresses earnings as a percentage of price. A PER of 20× therefore corresponds to a 5% earnings yield. The PER is only meaningful when EPS is positive: if the company is loss-making or EPS is zero, the ratio is undefined and this tool says so explicitly.
- PER = price ÷ EPS (lower can mean cheaper, higher can mean more expensive).
- Earnings yield = EPS ÷ price = 1 ÷ PER, shown as a percentage.
- Requires a positive price and positive EPS; a loss or zero EPS makes PER undefined.
How to use it
- Enter the share price.
- Enter the earnings per share (EPS) — use forecast EPS for a forward P/E, or last year's reported EPS for a trailing P/E.
- Read the PER and earnings yield on the right, then compare against the industry average and peers.
Reading the number: cheap or expensive?
There is no universal cutoff for a 'good' PER. Averages vary sharply by industry — high-growth sectors command higher multiples because investors pay up for expected future earnings, while mature sectors sit lower. Judge a PER against the industry average, comparable peers, and the company's own history. Watch for distortions, too: a one-off special gain temporarily inflates EPS and makes the PER look deceptively low, whereas a temporary loss shrinks EPS and pushes the PER up. Always check the quality and durability of the earnings behind the ratio.
Common use cases
- Quickly checking whether a stock is cheap or expensive relative to its earnings.
- Comparing the valuation of several companies in the same industry.
- Translating a P/E into an earnings yield to compare against bond yields.
