At one of Berkshire Hathaway's "Woodstock for Capitalists" events (also known as the annual shareholder meeting), Warren Buffett described the perfect business like this:

The ideal business is one that earns very high returns on capital and that keeps using lots of capital at those high returns. That becomes a compounding machine. So ... if you could put a hundred million dollars into a business that earns twenty percent on that capital -- twenty million -- ideally, it would be able to earn twenty percent on a hundred twenty million the following year and on a hundred forty-four million the following year and so on. You could keep redeploying capital at [those] same returns over time. But there are very, very, very few businesses like that.

Why so few? Think about a top-quality business like Wal-Mart (NYSE:WMT). If Wal-Mart reinvested all of its earnings into the business (which it doesn't), for a time it might be able to continue to deliver attractive returns on capital and compound its capital base.

But as a company gets increasingly large and has an ever-growing amount of available capital to deploy, finding high-rate-of-return opportunities to put capital to work can become difficult.

So in searching for Buffett's ideal stocks, we need to look for two things: high current returns on capital and plenty of opportunities to put new capital to work at similarly high returns.

Meet the returns royalty
Let's look at which companies are actually earning high returns on capital. To get us started, I ran a stock screen for companies with average five-year returns on capital above 15%. Here are five of the stocks that I came up with.

Company

Market Cap

Capital Base

Average 5-Year
Return
on Capital

Petrobras (NYSE:PBR)

$188 billion

$138 billion

17.3%

China Mobile (NYSE:CHL)

$184 billion

$74 billion

19.1%

Chevron (NYSE:CVX)

$155 billion

$101 billion

19.2%

Total (NYSE:TOT)

$141 billion

$109 billion

21.9%

Oracle (NASDAQ:ORCL)

$110 billion

$41 billion

18.9%

Source: Capital IQ, a Standard & Poor's company.
Capital base = total shareholder equity plus total debt.

Most of these are almost certainly names you recognize, and these are all great businesses that produce very attractive returns on capital.

However, the sheer size of these behemoths makes the continued reinvestment of earnings and compounding of sizable returns increasingly difficult. As with Wal-Mart above, it can be difficult for them to find high-return homes for all the money that's pouring in.

That's why most large companies deploy their earnings in ways other than reinvestment. Oracle, for instance, has put more than $13 billion toward share buybacks over the past five years and decided to start paying a dividend for the first time in 2009. Over roughly the same period, Chevron returned $43 billion to shareholders through buybacks and dividends.

So where can we find companies with high returns and the opportunity to reinvest new capital for high returns?

It's not the size of the company ... or is it?
The companies above could make great investments, but they're unlikely to be able to continue to compound their capital by reinvesting in the business. For that, we need to put on our reading glasses and look smaller.

While smaller, and often younger, companies aren't as established or stable as their huge counterparts, they typically have a greater ability to compound their capital through reinvesting in the business.

For many of these companies, the opportunity comes either from having only a small amount of capital to invest in a much larger market or from operating in a new, fast-growing market. The very best small caps combine market opportunity with a business that is head and shoulders above competitors.

For example, Boots & Coots is helping oil and gas exploration companies run better and safer, and has produced average returns on capital of 16% over the past five years while expanding its capital base from $8 million to more than $150 million.

Big-box retailer hhgregg, meanwhile, has been slowly but surely growing its store count and taking on Goliath-sized competitors like Best Buy (NYSE:BBY). hhgregg has delivered a 19% average return on capital while more than doubling its capital base.

Boots & Coots and hhgregg aren't the only companies with excellent businesses and room to run. The crew at Motley Fool Hidden Gems spends their time tracking down the very best small-cap stocks. Volcom, for instance, is part of Hidden Gems' real-money portfolio and would definitely fit Buffett's model. It's returned an average of 19% on its capital annually while more than doubling its total capital.

You can check out the entire Hidden Gems real-money portfolio, as well as all of the team's other recommendations by taking a free 30-day trial of the newsletter.

Fool contributor Matt Koppenheffer owns shares of Berkshire Hathaway, but does not own shares of any of the other companies mentioned. Best Buy and Berkshire Hathaway are Motley Fool Stock Advisor recommendations. Best Buy, Berkshire Hathaway, and Wal-Mart Stores are Motley Fool Inside Value selections. Petroleo Brasileiro and Total SA are Motley Fool Income Investor recommendations. Volcom is a Motley Fool Hidden Gems pick. The Fool owns shares of Volcom, Best Buy, and Berkshire Hathaway. The Fool's disclosure policy is impressed that Matt finally made it through Buffett's biography.