One of the best investments we can make is in our own knowledge and skill set. With that in mind, this article will work through how we can use Return On Equity (ROE) to better understand a business. We'll use ROE to examine WINDMILL Group Limited (HKG:1850), by way of a worked example.

Over the last twelve months WINDMILL Group has recorded a ROE of 23%. Another way to think of that is that for every HK$1 worth of equity in the company, it was able to earn HK$0.23.

Want to participate in a short research study? Help shape the future of investing tools and you could win a $250 gift card!

Check out our latest analysis for WINDMILL Group

How Do I Calculate ROE?

The formula for ROE is:

Return on Equity = Net Profit ÷ Shareholders' Equity

Or for WINDMILL Group:

23% = HK$28m ÷ HK$123m (Based on the trailing twelve months to October 2018.)

Most readers would understand what net profit is, but it’s worth explaining the concept of shareholders’ equity. It is the capital paid in by shareholders, plus any retained earnings. Shareholders' equity can be calculated by subtracting the total liabilities of the company from the total assets of the company.

What Does Return On Equity Signify?

ROE measures a company's profitability against the profit it retains, and any outside investments. The 'return' is the profit over the last twelve months. The higher the ROE, the more profit the company is making. So, all else equal, investors should like a high ROE. That means ROE can be used to compare two businesses.

Does WINDMILL Group Have A Good Return On Equity?

By comparing a company's ROE with its industry average, we can get a quick measure of how good it is. Importantly, this is far from a perfect measure, because companies differ significantly within the same industry classification. As is clear from the image below, WINDMILL Group has a better ROE than the average (10%) in the Commercial Services industry.

That is a good sign. In my book, a high ROE almost always warrants a closer look. For example you might check if insiders are buying shares.

The Importance Of Debt To Return On Equity

Virtually all companies need money to invest in the business, to grow profits. That cash can come from retained earnings, issuing new shares (equity), or debt. In the case of the first and second options, the ROE will reflect this use of cash, for growth. In the latter case, the use of debt will improve the returns, but will not change the equity. Thus the use of debt can improve ROE, albeit along with extra risk in the case of stormy weather, metaphorically speaking.

WINDMILL Group's Debt And Its 23% ROE

Although WINDMILL Group does use a little debt, its debt to equity ratio of just 0.058 is very low. When I see a high ROE, fuelled by only modest debt, I suspect the business is high quality. Conservative use of debt to boost returns is usually a good move for shareholders, though it does leave the company more exposed to interest rate rises.

The Bottom Line On ROE

Return on equity is useful for comparing the quality of different businesses. A company that can achieve a high return on equity without debt could be considered a high quality business. If two companies have around the same level of debt to equity, and one has a higher ROE, I'd generally prefer the one with higher ROE.

Having said that, while ROE is a useful indicator of business quality, you'll have to look at a whole range of factors to determine the right price to buy a stock. It is important to consider other factors, such as future profit growth -- and how much investment is required going forward. Check the past profit growth by WINDMILL Group by looking at this visualization of past earnings, revenue and cash flow.

Of course WINDMILL Group may not be the best stock to buy. So you may wish to see this free collection of other companies that have high ROE and low debt.

We aim to bring you long-term focused research analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material.

If you spot an error that warrants correction, please contact the editor at editorial-team@simplywallst.com. This article by Simply Wall St is general in nature. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. Simply Wall St has no position in the stocks mentioned. Thank you for reading.