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 its ROIC, you can see how well a company is 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 from 8% to 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 ExxonMobil (NYSE: XOM) 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

ExxonMobil

9%

16.3%

24.3%

20.6%

Chevron (NYSE: CVX)

10.2%

9.8%

15.4%

16%

ConocoPhillips (NYSE: COP)

6%

NM

7.4%

11.5%

Source: Capital IQ, a division of Standard & Poor's. NM = not meaningful; Conoco reported a net loss for the period.

ExxonMobil has met our 12% threshold for attractiveness in each of the above periods except the most recent, but its returns have declined from five years ago. The returns of Chevron and ConocoPhillips are also off from five years ago, and Conoco has not met our 12% threshold for attractiveness in the past five years. I'd really like to see those returns increase, but that, of course, has a lot to do with oil and gas prices.

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. Chevron is a Motley Fool Income Investor recommendation. The Fool owns shares of ExxonMobil. Try any of our Foolish newsletter services free for 30 days. The Motley Fool has a disclosure policy.