Price-earnings ratios of ETFs are easy to find

— -- Q: How can I get the price-to-earnings ratio of an exchange-traded fund (ETF)?

A: Some investors use price-to-earnings ratios (P-Es) to determine how cheap or expensive a stock is.

The P-E ratio is the price of a stock divided by its earnings. You can either divide by past earnings, to get the trailing P-E, or future expected earnings, to get the forward P-E. The higher the P-E, the more investors are paying for each dollar in earnings the company is generating.

You can do the same analysis for exchange-traded funds. You can get the P-E of an ETF from:

•The provider of the underlying index. ETFs are investments that own the stocks in an index. That means if you can get the P-E of the index, you know the P-E of the ETF. Some popular indexes provide their P-E ratios. Say you're invested in an ETF that tracks the Standard & Poor's 500 index. You can get the P-E of the S&P 500 here.

•Morningstar. Log onto www.morningstar.com and enter the ETF's ticker symbol. Next, click on the "portfolio" option on the left-hand side of the screen. Scroll down and you'll see the ETF's "price/prospective earnings" and how it compares to the S&P 500.

Matt Krantz is a financial markets reporter at USA TODAY. He answers a different reader question every weekday in his Ask Matt column at money.usatoday.com. To submit a question, e-mail Matt at mkrantz@usatoday.com.