When investors look at a stock, one of the first numbers they turn to is the price-to-earnings (P/E) ratio. It has long been the standard for evaluating whether a company is overvalued or undervalued. A low P/E ratio often signals a bargain, while a high P/E ratio can suggest that optimism has already been priced in. For decades, this simple measure has helped investors compare companies across industries and time periods.
Yet the P/E ratio has limits. And in today’s market, with fast-growing tech firms and disruptive startups taking center stage, those limits are impossible to ignore. Many of the companies leading innovation today don’t even have a P/E ratio at all—because they aren’t generating positive earnings. Instead, they have negative P/E ratios, which signals they are losing money. That does not automatically mean they are poor investments, but it does mean you cannot use the traditional P/E framework to understand their value.
When P/E Ratios Don’t Work
Negative P/E ratios often show up in companies that are reinvesting heavily into their own growth. Cloud computing, artificial intelligence, biotech, and other fast-moving industries frequently have leaders who spend more than they earn in order to capture market share. In these cases, comparing P/E ratios across companies simply doesn’t work, because the math breaks down when earnings are negative.
This is where many investors make mistakes. They either dismiss the stock altogether because of negative earnings, or they assume traditional valuation tools will still apply. But just as an investor in the 1990s could not evaluate Amazon with the same tools used for an industrial manufacturer, today’s growth stocks require a different lens.
Why the P/S Ratio Matters
The price-to-sales (P/S) ratio offers that lens. Instead of focusing on earnings, the P/S ratio measures a company’s stock price relative to its revenue. Since even cash-burning companies have revenue, this metric gives investors a way to compare growth companies on common ground.
The P/S ratio is calculated by dividing the company’s market capitalization by its total sales. Like the P/E ratio, it offers a sense of valuation. A P/S ratio above 1 can indicate the stock is overvalued relative to its sales, while a P/S ratio below 1 suggests it may be undervalued. The range varies across industries, but the rule of thumb holds: lower is generally better, provided the company has strong fundamentals and growth prospects.
For example, when comparing two cloud computing companies with negative P/E ratios, the P/S ratio can help identify which one investors are paying a premium for. It highlights how much the market values each dollar of revenue, which is often the best proxy for potential in industries where earnings take a back seat to growth.
A Hidden Tool Even Experts Overlook
This is not a new idea, but it remains underused. Many retail investors focus exclusively on the P/E ratio, and even seasoned professionals sometimes ignore the P/S ratio when assessing companies in high-growth sectors. But if you want to understand the relative valuation of emerging leaders—especially those that have yet to turn a profit—the P/S ratio is indispensable.
Knowing when and how to use it is an expert tip that can give you a sharper edge in analyzing opportunities. Growth investing often requires looking past traditional metrics to find the tools that best match the business model. In today’s market, the P/S ratio is one of those tools.
Bottom Line
The P/E ratio has earned its place as a cornerstone of stock analysis. But it is not universal. For companies with negative earnings, especially in fast-moving industries like tech and biotech, it tells you little about actual value. The P/S ratio fills that gap, giving investors a way to compare growth companies on more reliable terms.
If you want to invest confidently in companies that are building the future, add the P/S ratio to your toolbox. It can reveal opportunities, and risks, that traditional measures leave hidden.
Next Steps
Contact Michael Leslie Investments today to learn how our team can help you apply the right valuation tools for your portfolio. With expert guidance, you can better position your investments for long-term growth.
