What is Price-to-Earnings (P/E) Ratio?


The price-to-earnings ratio (P/E ratio) is a tool used to determine a company’s value, and can alternatively be referred to as the earnings multiple or price multiple. Utilised by investors and analysts, this calculation measures the current share price against earnings-per-share (EPS).

Such information provides insight into the comparative value of stock and demonstrates whether a company is currently undervalued or overvalued. It can also indicate whether investors anticipate future growth. By examining historical patterns, a company might use the ratio to analyse its performance over time, while it can similarly be employed by analysts to make comparisons between aggregate markets.

So, what is a good P/E ratio? There is no simple answer to this question, as it depends on how it is being calculated and what it is being used for. 

P/E ratio formula and calculation

The calculation for P/E ratio is quite straightforward, you just divide the market value per share by the earnings per share:

P/E ratio = Market-value-per-share ÷ Earnings-per-share

For example, if the share price is $10 for a company earning $1 per share, then the P/E ratio is 10x.

Of course, EPS can be determined in different ways, resulting in the two most commonly used varieties of P/E ratio: trailing and forward. The trailing variety examines earning performance over the previous year, while the forward calculation incorporates the anticipated future share earnings to determine the ratio.

A separate construction of P/E ratio looks at longer term trends by considering earnings averages over 10 years (P/E 10) or even 30 years (P/E 30). This can be useful in accounting for fluctuations in the overall business cycle, particularly when looking at the value of a stock index overall.

Forward price-to-earnings

Using forward estimates of EPS to determine P/E ratio is valuable when considering the projected value of a business. However, as this is only based on an educated guess, and therefore subject to a number of variables, the metric can be unreliable. For instance, a company may have its own reasons to underestimate or overestimate future earnings. The forward-focused calculation is, therefore, the less common of the two.

Trailing price-to-earnings

Trailing P/E employs the more concrete calculation of EPS based on the past 12 months. As long as earnings have been reported correctly, this is a more objective metric that many investors trust, as it is not based on a guess. However, this does not mean that trailing ratio is the perfect measure. For instance, in considering only past performance, it cannot take future growth into account.

Valuation from P/E

P/E can be used in different ways. It might not be the only metric that values stock, but it is one of the most commonly used. At its simplest level, the ratio reveals what the current market is prepared to shell out for stock based on earnings, past or future, and therefore reveals what people are prepared to invest for each dollar earned. For instance, at a P/E of 10x, you would expect to earn $1 for every $10 you pay.

An example of the P/E ratio

Taking the Coles Group as an example, the share price at the start of 2020 was at $16.15, with a trailing EPS of 89 cents. Therefore P/E is calculated as:

16.15 ÷ 0.89 = 18.16

When rounded, this can be expressed as a ratio of 18.2x. Or, put another way, investors paid around $18.20 for every dollar earned (based on the previous year). This number is particularly useful in determining the value of Coles stock when compared with other operators in the same industry group.

Investor expectations

P/E tells us a number of things about shareholder expectations. A relatively low ratio could mean that investors believe the company is struggling to perform as well as others in the same industry, or it may purely show that the stock is simply undervalued. Conversely, a high P/E might indicate how investors anticipate growth in future earnings for that stock.

P/E compared to earnings yield and price-to-earnings-to-growth (PEG) ratio

Of course, P/E ratio is not the only measure around. Other metrics sometimes used to assess company value include the earnings yield and the PEG ratio.

Earnings yield

This metric is the inverse of P/E, where EPS is divided by the share price and expressed in percentage form. Accordingly, this provides the same information as P/E, just in a different manner. While earnings yield places the focus on the rate of return for the investment, P/E ratio is more commonly used, as it provides a more direct focus on growth in value over time. Furthermore, earnings yield assists analysis where a company has no earnings (or even negative earnings), while P/E will not be useful here.

PEG ratio

The PEG ratio is a variation on P/E that provides more comprehensive information by taking account of the connection between P/E and the growth in earnings. A low PEG (under 1) indicates that the share price underestimates earnings growth, with a higher figure (above 1) showing how investors have overestimated growth. PEG is an example of how P/E can be used in other calculations to reveal even more about stock value.

Absolute vs. relative P/E

You may also come across references to absolute and relative P/E. The absolute ratio is calculated in the usual fashion detailed above (based on the current EPS), whereas relative P/E compares against a benchmark of past ratios across a particular time frame, such as 5 or 10 years. When talking about P/E, it is the absolute metric that is generally accepted as the common standard metric. However, the relative ratio can be a useful tool for taking into account developments over time.

P/E ratio limitations and other possible considerations

As worthwhile as this ratio is, all we end up with is a number that can be interpreted in various ways, and which, therefore, does come with certain limitations. It is particularly beneficial when comparing companies within a particular industry. However, it is not an absolute measure that can be used to effectively compare across different sectors, such as how investment in a retail company stacks up against particular finance stock. Similarly, P/E does not effectively deal with companies that are not profitable.

The P/E ratio has many applications for investors, companies, and analysts, but it is important to have a strong understanding of what it means and how it is used in order to get the best use out of it. When employed correctly, it can provide very meaningful insight into stock value

It is certainly not the only metric of its kind, but it is one of the most important and widely used.