How is a P/E multiple used?

Is a stock trading at a P/E of 30 more expensive than a stock trading at a P/E of 60? Such a wide variation in P/E multiples can be owing to a few reasons. If the companies are in the same industry, it could be that the company with a high P/E may be one with superior size and financials, with better prospects or even better management. The market expects this stock to outperform its peers. If they are from different industries, it could also be due to different growth prospects. For example, an energy utility will have a more sedate earnings profile than say a software company.

Stock prices, in isolation do not give any indication whether the stock is undervalued or overvalued. They have to be viewed along with the company's future prospects to arrive at any conclusion. Generally, higher the expected growth in a company's earnings, higher is the P/E multiple that it attracts in the market. The time period used for P/E calculations depends on the investment horizon of the investor and would be different for each investor. However, P/E multiples cannot be applied to loss making companies since they do not have any earnings.