P/E Ratio Calculator

A price-to-earnings (P/E) ratio calculator divides a company's share price by its earnings per share to show how much investors are paying for each pound of earnings. It is one of the most widely used valuation metrics in equity analysis, used by investors and analysts to compare companies and assess whether a stock appears expensive or cheap relative to its earnings.

How to Use the P/E Ratio Calculator

1. Enter the current share price of the company.
2. Enter the earnings per share (EPS), which is typically the most recent annual figure or the trailing twelve months.
3. The calculator divides the share price by EPS to give the P/E ratio.
4. Optionally enter a forward EPS estimate to calculate the forward P/E.
5. Compare the result to the company's historical average, its sector peers, and the broader market index.

The Formula

P/E Ratio = Share Price / Earnings Per Share

Where Share Price is the current market price of one share and EPS is the company's net profit divided by the number of shares in issue. A trailing P/E uses actual historical earnings. A forward P/E uses analysts' consensus earnings forecast for the next twelve months.

Real-World Example

A company has a share price of £24.60 and reported earnings per share of £1.64 for the past twelve months.

P/E Ratio = £24.60 / £1.64 = 15.0

This tells you that investors are paying 15 times the company's annual earnings for each share. If analysts forecast EPS of £1.90 next year, the forward P/E is £24.60 / £1.90 = 12.9, suggesting the stock may look cheaper on a forward basis. A P/E of 15 is close to long-run average market multiples for major developed markets, though sector context is essential for proper interpretation.

What P/E Ratios Tell You About a Market

A high P/E relative to peers or history can indicate that investors expect strong future earnings growth, that the stock is overvalued, or both. A low P/E can indicate undervaluation, weak growth expectations, or genuine fundamental problems. Growth sectors such as technology typically trade at higher multiples than value sectors such as utilities or financial services. The market-wide cyclically adjusted P/E ratio, known as the CAPE or Shiller P/E, smooths earnings over 10 years to reduce the distortion of short-term earnings cycles, providing a longer-term perspective on market valuation.

Frequently Asked Questions

What is a good P/E ratio? There is no universal good P/E, as the appropriate multiple depends on the company's growth rate, sector, and market conditions. Historically, the UK stock market has traded at a trailing P/E of around 12-18 times. A fast-growing technology company might reasonably trade at 30 or more times earnings.

What is the difference between trailing and forward P/E? Trailing P/E uses reported historical earnings, which are factual but backward-looking. Forward P/E uses consensus earnings estimates for the coming year, which are more relevant for valuation but carry the risk of forecast error.

Can the P/E ratio be negative? Yes, if a company has reported a loss, its EPS is negative, making the P/E ratio meaningless or negative. In such cases, other valuation metrics such as price-to-sales or EV/EBITDA are used instead.

Should I buy a stock with a low P/E? Not automatically. A low P/E can indicate a value opportunity, but it can also reflect genuine problems with the business, declining earnings, or sector-wide headwinds. Always examine why a stock trades at a low multiple before concluding it is cheap.

Reading the multiple as an earnings yield

The P/E ratio and the earnings yield are two ways of writing the same relationship. The earnings yield is the reciprocal of the multiple, expressed as a percentage: 100 divided by the P/E. It answers the opposite question, which is what a pound of share price buys in annual earnings.

At the page's trailing multiple of 15.00 the earnings yield is 100 / 15 = 6.67 percent. At the forward multiple of 12.95 it is 100 / 12.95 = 7.72 percent, so the forward figure works out about 1.06 percentage points higher on the same share price. That gap is the whole point of a forward multiple: it prices today's price against earnings the company has not yet reported.

A 20.00 percent earnings yield means the company earns a fifth of its market value in a year. A 2.00 percent yield means the market value sits at fifty times that annual earnings figure. Neither number settles whether the share is a good purchase by itself, because the yield has to be read against what the same money would earn elsewhere.

The same share price against four different earnings figures

Hold the share price at £24.60 and change only the earnings per share. The multiple does all of the moving, because EPS sits underneath the division.

The first two rows carry the same share price. An investor holding £1.20 of earnings pays a multiple about 37 percent higher than one holding £1.64, and nothing about the company's price changed. The last two rows give the earnings needed to bring the same £24.60 down to a multiple of 12 or 10.

Trailing against forward on the page's own figures

The page's company reports £1.64 of trailing earnings per share and is forecast to earn £1.90 next year. The forecast sits 15.85 percent above the reported figure: (1.90 minus 1.64) divided by 1.64 gives 0.1585.

The page prints the forward multiple as 12.9. The division gives 12.9474, so 12.9 is the same value at one decimal place rather than a different result. Everything below uses 12.95, because a reader recomputing at two decimals will land there.

Working backwards from a target multiple

Run the same division the other way and the ratio becomes a target rather than a result. Given a multiple you are willing to pay and a share price, the required EPS is the price divided by the target.

Moving the multiple from 15 to 10 at a fixed price takes half again as much earnings. That is the arithmetic behind the page's warning about low multiples. The gap between a multiple of 15 and one of 10 can close through a higher share price, through higher earnings, or through some of each, and the two routes say different things about the business.

How far the multiple moves when earnings move

Earnings estimates are revised through the year, and no other input on the page moves the ratio as much per unit of change.

The response is not symmetrical. A 10 percent cut in earnings lifts the multiple 11.1 percent, from 15.00 to 16.67, while a 10 percent rise in earnings lowers it only 9.1 percent, to 13.64. The same sized revision moves the ratio further when earnings fall than when they rise, because EPS sits in the denominator.

Growth, PEG, and where that shorthand stops working

The PEG ratio divides the multiple by the expected annual growth rate in percentage points. At the page's 15.00 and a growth assumption of 10 percent, PEG is 15 / 10 = 1.50. At 6 percent growth the same multiple gives 15 / 6 = 2.50. On the forward multiple of 12.95 with 10 percent growth, PEG is 12.95 / 10 = 1.30.

A common shorthand treats a PEG near 1 as fairly priced, above it as expensive and below it as cheap. Read that as a screening habit rather than a valuation. It assumes the growth rate is both right and sustainable, and it has no meaning at all for a company with no earnings to divide by.

What the division assumes and what it leaves out

The calculation is one division on two numbers, and everything it cannot see sits outside the fraction.

• The denominator comes from reported accounts, which follow the company's own accounting policy. Depreciation, one-off items and share-based pay all move reported EPS without moving cash.
• The share count changes. A buyback cuts the number of shares and lifts EPS with no improvement in profit, which lowers the multiple.
• The price is live and the earnings are historical. The trailing multiple puts a price quoted this minute against an earnings figure reported up to a year ago.
• Borrowings are invisible in the ratio. Two companies at the same multiple can carry very different debt, which is where the page sends the reader to EV/EBITDA and price-to-sales for a fuller picture.
• A loss breaks it. Negative EPS gives a negative or meaningless multiple, and the page says so in its own FAQ.

Three checks before acting on the number

1. Work out the earnings yield, 100 divided by the P/E, and put it beside the yield on a government bond of similar duration. The comparison is rough and it still carries more information than the bare multiple.
2. Put the same company's multiple for the last five years next to today's figure, so the comparison runs against its own history rather than an abstract band.
3. Read the note behind the EPS figure and establish whether it is statutory, adjusted or diluted. Adjusted EPS usually flatters the multiple, and diluted EPS usually adds to it.

The market average against a single share

The page cites a UK trailing band of roughly 12 to 18 times. The example's trailing 15.00 sits inside that band and the forward 12.95 sits just above its floor. A multiple outside the band is not on its own a signal either way, because the band averages over sectors that earn money in very different ways. A regulated utility with predictable cash flows and a software company with most of its value in future growth cannot be ranked on one number.

The cyclically adjusted P/E the page mentions smooths portfolio earnings over ten years, so one strong or weak year leaves far less of a mark on it. It is a slower number and it moves less than the trailing multiple on the same index, which is exactly why it is used for long-run comparison rather than for timing.

Every figure in the tables above comes from the page's own example, £24.60 and £1.64, with the forward EPS of £1.90 as the page gives it. Each earnings yield is 100 divided by the multiple printed in the same row, rounded to three decimal places so a reader can reproduce it exactly. Where a yield lands a hundredth away from a value computed at one decimal place, the difference is the rounding of the multiple rather than a different result.

Also try these free tools:

• Price-to-Book
• Price-to-Sales
• EPS Calculator