Price-to-Earnings Ratio

A stock is a small share in a company. Whoever buys it gets a claim on a portion of the profit the company generates. The price-to-earnings ratio compares these two things: the price of the stock on the market and the profit that, mathematically, is attributable to that one share. You divide the price by the earnings and get a single number. If a stock costs 60 euros and 3 euros of annual profit is attributable to it, the price-to-earnings ratio is 20. Put simply: you are paying today as much as the company will earn in profit for this share over the next 20 years — assuming the profit stays at the same level.

What the number reveals about a stock’s price

The raw share price says almost nothing. A stock priced at 800 euros can be cheap, while one at 4 euros can be wildly overpriced. What matters is the relationship between the price and what the company actually earns. This is exactly the conversion the price-to-earnings ratio performs. It is what makes it possible to compare companies of very different sizes in the first place.

A high value does not automatically mean a stock is bad. Above all, it shows that the market has high expectations. Investors assume that profits will rise sharply. Conversely, a low value can point to a bargain — or to the fact that nobody believes in the company’s future. So the metric raises a question rather than providing an answer.

For technology and AI companies, the values are often particularly high. There, investors are paying for expected growth, not for today’s profit. That is exactly why the price-to-earnings ratio comes up whenever there is talk of a possible bubble. If prices rise much faster than profits, the ratio grows — and so does the nervousness.

The calculation and its pitfalls

The formula is simple: share price divided by earnings per share. Earnings per share is obtained by dividing the company’s annual profit by the total number of shares issued. If a company earns 300 million euros and there are 100 million shares, that comes to 3 euros per share. This figure appears in every annual report and does not need to be calculated yourself.

What matters is which profit figure is used. If you use last year’s profit, this is called the trailing price-to-earnings ratio. If instead you use analysts' profit estimate for the coming year, you get the forward price-to-earnings ratio. For fast-growing companies, the two figures can differ significantly. So anyone comparing numbers needs to know which variant is being referred to.

The metric has clear limitations. If a company makes a loss, it cannot even be calculated, since dividing by a negative number makes no sense. In addition, the reported profit can be influenced by accounting rules, such as depreciation or one-off special items. And comparisons across industries are often misleading: software companies traditionally have higher values than carmakers or banks. A meaningful comparison is only possible within the same industry or against a company’s own history.

The P/E ratio in market news and trading apps

In financial news, the abbreviation P/E is everywhere. Sentences like “The stock is ambitiously valued with a P/E of 45” simply mean: it is expensive relative to its profit. The metric is also calculated for entire stock indices, such as the DAX or the US index S&P 500. If it is significantly above the long-term average, commentators are quick to warn of overheating.

Every broker app and every financial portal displays the figure on a stock’s overview page, usually right next to the price and the dividend. There it is often found under its English name, P/E Ratio, short for price-earnings ratio. Behind it lies exactly the same calculation.

A common misconception is to read the metric as a buy signal. It is a snapshot and completely ignores debt, growth rate, and competitive position. Professionals therefore combine it with other figures, such as the price-to-sales ratio. Still, as a quick first impression, the price-to-earnings ratio is hard to beat.