ValuationBeginner

What is the P/E ratio

PER divides price by earnings per share. It expresses how many times you pay the current or expected annual profit, but is only useful if that profit reasonably represents the economics of the business.

3 min read Practical guide

By the end

You will interpret historical and future P/E without automatically concluding that low is cheap.

Calculation

PER = price / EPS. Trailing uses past profit; the forward, estimates. It is also equivalent to capitalization / attributable profit if dates and actions are consistent. A negative profit makes the ratio insignificant.

What it contains

A high P/E may reflect growth, duration, stability or low rates; a low one can signal cyclicality, debt or deterioration. The multiple compresses many assumptions, which is why they must be broken down.

Example

Company A at 30x grows EPS 20% and reinvests well; B at 10x is in a cyclical peak and its profit may fall 50%. B is not necessarily cheaper.

Valid comparisons

Compare with your own history adjusted to the cycle and with similar models. Ensures same definition of EPS and debt. Banks, software and manufacturers do not deserve the same framework.

From ratio to decision

Projects normalized EPS and a range of multiples consistent with growth and risk. Calculate return including dividends and possible contraction. Contrast with FCF to detect profit without cash.

Trailing or forward.

GAAP or adjusted.

Normalized profit.

Growth and balance.

Range, not single point.

From data to a decision

Do earnings justify the multiple?

This guide cannot predict the next move on its own. It can build a conditional reading: what supports upside, what increases downside risk, and which evidence must appear before acting.

Favourable reading

Durable growth, cash conversion, and low risk support a higher P/E.

Adverse reading

Peak cyclical earnings or aggressive adjustments make the P/E look cheap.

Required confirmation

Use normalized EPS and test historical and peer multiples.

Reasoned example

10x peak EPS of 10 may be more expensive than 20x normalized EPS of 6.

Applied workshop

Turn the explanation into a process

Follow these steps in order and keep the result, so you can repeat the analysis and identify what changed your decision.

1Normalise earnings for the cycle, one-offs and diluted shares.
2Compare current, historical and peer P/E after adjusting growth, margin, balance sheet and quality.
3Break expected return into EPS growth, dividends and multiple change.
4Stress a multiple contraction even if forecast earnings are achieved.

Review questions

Is the denominator sustainable?
Which growth rate justifies the multiple?
Would the investment remain attractive without P/E expansion?

Worked case

Low PER on a cyclical peak

A manufacturer earns €10 per share at the peak of the cycle and is trading at 80: PER 8. If normalized profit is €4, you really pay 20 times. Another company at PER 25 with stable growth may be less risky.

Project normalized EPS, debt and exit multiple. Check FCF to detect adjustments that inflate profit.

Decision rule

A PER is only cheap if the profit is sustainable and the risk does not require a greater discount.

Put it into practice

Calculate the price in three years with adverse, central and favorable EPS and various P/E; annualize each result.