We'd all like to invest as successfully as the legendary Warren Buffett. He calculates return on invested capital (ROIC) to help determine whether a company has an economic moat -- the ability to earn returns on its money beyond that money's cost.

ROIC is perhaps the most important metric in value investing. By determining a company's ROIC, you can see how well it's using the cash you entrust to it, and whether it's actually creating value for you. Simply put, ROIC divides a company's operating profit by the amount of investment it took to get that profit:

ROIC = Net operating profit after taxes / Invested capital

This one-size-fits-all calculation cuts out many of the legal accounting tricks (such as excessive debt) that managers use to boost earnings numbers, and provides you with an apples-to-apples way to evaluate businesses, even across industries. The higher the ROIC, the more efficiently the company uses capital.

Ultimately, we're looking for companies that can invest their money at rates that are higher than the cost of capital, which for most businesses lands between 8% and 12%. Ideally, we want to see ROIC greater than 12%, at minimum. We're also seeking a history of increasing returns, or at least steady returns, which indicate that the company's moat can withstand competitors' assaults.

Let's look at Home Depot (NYSE: HD) and two of its industry peers to see how efficiently they use capital. Here are the ROIC figures for each company over several time periods:

Company

TTM

1 Year Ago

3 Years Ago

5 Years Ago

Home Depot

11.9%

11.3%

13.1%

20.1%

Lowe's (NYSE: LOW)

8.6%

8.7%

14.7%

16.0%

Lumber Liquidators (NYSE: LL)

23.9%

27.0%

21.4%

38.9%*

Source: Capital IQ, a division of Standard & Poor's. *For fiscal 2005. TTM = trailing 12 months.

Each of these home-improvement retailers has shown a decline from five years ago. While Home Depot barely misses the 12% return on invested capital we are looking for, it displays consistent decreases across five years. Lowe's displays a similar downward trend. Only Lumber Liquidators meets our 12% threshold for attractiveness, and shows an increase in its ROIC from three years ago.

Businesses with consistently high ROIC are efficiently using capital. They can use their extra returns to buy back shares, further invest in their future success, or pay dividends to shareholders. (Warren Buffett especially likes that last part.)

To unearth more successful investments, dig a little deeper than the earnings headlines, and check up on your companies' ROIC.

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Jim Royal, Ph.D., does not own shares in any company mentioned. Home Depot and Lowe's Companies are Motley Fool Inside Value choices. Lumber Liquidators Holdings is a Motley Fool Rule Breakers selection. The Fool owns shares of Lowe's Companies. Try any of our Foolish newsletter services free for 30 days.