What is the price-to-earnings (P/E) ratio?
The P/E ratio is the share price divided by earnings per share, showing how much investors pay for each rupee of a company's annual profit.
The price-to-earnings (P/E) ratio is the single most common valuation yardstick in the stock market. It compares a company's share price to its earnings per share (EPS):
P/E = share price ÷ earnings per share.
If a stock trades at Rs 100 and earned Rs 10 per share last year, its P/E is 10. The intuitive reading is that investors are paying Rs 10 for every Rs 1 of annual profit the company generates. Another way to see it: at a P/E of 10, the company would take ten years to earn back its current price in profits, if earnings stayed flat.
The P/E ratio is so popular because it offers a quick sense of how cheap or expensive a stock is relative to its profits, and lets you compare companies of different sizes and prices on a common footing.
Interpreting P/E requires context:
- A low P/E can mean a stock is undervalued — or that the market expects its earnings to decline, or sees higher risk. Cyclical and out-of-favour sectors often trade on low P/Es. - A high P/E can mean a stock is overvalued — or that investors expect strong future growth and are willing to pay up for it. Fast-growing companies routinely carry high P/Es.
So a P/E is never "good" or "bad" in isolation. It must be compared against the company's own history, its sector peers, and the overall market. The PSX as a whole has often traded at relatively low P/Es compared with global markets, reflecting local risk and macro conditions, so a "cheap" P/E for a Pakistani stock should be judged against local norms.
Some important nuances:
- Trailing vs forward P/E. Trailing P/E uses the last reported earnings; forward P/E uses expected earnings. A high trailing P/E may look reasonable on forward earnings if profits are set to jump. - Earnings quality. Because EPS sits in the denominator, one-off gains or losses can distort the P/E. A suspiciously low P/E may rest on unsustainable earnings. - Loss-making companies. A company with no profit has no meaningful P/E, so other measures are needed.
Used thoughtfully — alongside growth prospects, debt, return on equity, and sector context — the P/E ratio is an excellent first filter for spotting potentially cheap or expensive stocks. Used naively, it can mislead, because a number this simple inevitably leaves a lot out.