What Is the P/S Ratio and How Is It Calculated?

Simply put, the Price-to-Sales (P/S) ratio tells you “how much you’re willing to pay for each dollar of a company’s sales.”^[1] The formula is: P/S = Stock Price ÷ Sales per Share. Sales per Share = total revenue over the past 12 months ÷ number of outstanding shares (adjusted for stock splits).^[1] You can also use market cap divided by total revenue—the result is the same.^[2] For example, if a company has a market cap of $30 billion and trailing 12-month revenue of $10 billion, its P/S is 3x. Both methods are essentially the same because market cap = price × shares, and total revenue = revenue per share × shares; canceling shares gives the same result.

Example: Suppose a company has annual revenue of $10 billion and 1 billion shares outstanding. Revenue per share is $10. If the stock price is $30, then P/S = 30 ÷ 10 = 3x. This means investors are paying $3 for every $1 of the company’s annual sales.^[3] Think of this multiple as a “sales premium”—you’re buying the company’s revenue stream, not its profits.

Why Can You Still Use P/S to Value a Company That Is Losing Money and Has No Net Profit?

This is P/S’s biggest superpower. When a company’s net profit is negative, the P/E ratio becomes negative or shows “N/A,” making it completely useless.^[4] But P/S only cares about revenue, not net profit, so even if the company is losing money, P/S still gives you a positive number to work with.^[4] For instance, a company with $1 billion in annual revenue and a $5 billion market cap has a P/S of 5x. This number doesn’t turn negative just because the company is unprofitable. You can compare it to peers to gauge whether the market is overhyped.

That’s why P/S is especially useful for companies that aren’t yet profitable but are growing revenue fast—like many SaaS (software-as-a-service), biotech, and newly listed companies.^[4] These companies may still be burning cash on R&D or expansion, but their revenue is already growing quickly. P/S helps you measure how much the market is paying for that growth. To learn about another common metric, check out our previous article: What Is the P/E Ratio? How to Calculate It and What’s Considered Expensive?

What’s the Difference Between P/S and P/E, and Which One Should You Use?

The core difference: P/E looks at profit, while P/S looks at revenue. P/E = Stock Price ÷ Net Profit per Share, so it breaks when the company isn’t profitable. P/S = Stock Price ÷ Sales per Share, so it works even when the company is losing money.^[4] Think of it this way: P/E is like looking at how much money someone has saved (profit), while P/S is like looking at how much they earn (revenue). If someone just started working and has debt (losses), looking at savings is meaningless, but looking at their salary still tells you about their income level.

So which one should you use? If you’re looking at mature, profitable companies, P/E is more common. For unprofitable growth stocks, P/S is more appropriate. But neither is a silver bullet—it’s best to use them together. For example, a company with a low P/E but a high P/S might have high profit margins but low expected revenue growth. Conversely, a company with a negative P/E but a very low P/S might indicate the market is extremely pessimistic about its revenue prospects. Also, What Is the P/B Ratio? Applicable Industries, Calculation, and Examples can help you value a company from an asset perspective.

How Is P/S Different from EV/Sales, and Why Is the Latter More Accurate?

P/S only considers equity market cap and completely ignores a company’s debt and cash.^[7] For example, two companies with the same revenue—one drowning in debt and the other sitting on a pile of cash—would have the same P/S, which doesn’t make sense. Suppose Company A has a $10 billion market cap, no debt, and $1 billion in cash; Company B has a $10 billion market cap, $5 billion in debt, and $0.5 billion in cash. Both have the same P/S, but Company B is much riskier because its enterprise value (market cap + debt – cash) is higher.

EV/Sales (enterprise value-to-sales) solves this problem: it uses enterprise value (market cap + debt – cash) divided by revenue, accounting for both debt and cash.^[7] For companies with very different capital structures, EV/Sales is more accurate than P/S.^[8] However, P/S is simple and intuitive, so it’s still widely used for quick comparisons among companies in the same industry. If the companies you’re comparing have similar debt levels, P/S is fine. But if one is highly leveraged, it’s better to use EV/Sales.

What Is the Biggest Flaw of the P/S Ratio?

P/S’s biggest flaw is that it completely ignores a company’s profitability and cost structure.^[6] Example: Two companies each have $1 billion in revenue. Company A has a 30% net profit margin (earning $300 million), while Company B has a 5% net profit margin (earning only $50 million). P/S would value them identically, but clearly Company A is much better at making money.^[6] So P/S is like looking at someone’s income without considering their expenses—someone with high income but even higher spending won’t actually save any money.

Another flaw is that P/S ignores debt levels.^[7] Highly leveraged companies may appear cheap on P/S, but they actually carry higher risk. For example, a company might have high revenue, but if most of its profits are eaten up by interest payments, a low P/S doesn’t mean it’s a bargain. That’s why P/S should never be used alone—it must be paired with metrics like gross margin, net margin, and debt-to-equity ratio.^[10] For a more comprehensive way to value growth stocks, check out What Is the PEG Ratio? A Detailed Guide to Valuing Growth Stocks.

What Is a Reasonable P/S? When Is It Overvalued?

There’s no absolute standard because P/S varies hugely by industry. Retail companies typically have very low P/S (often below 1x) because profit margins are thin and revenue is large. Software companies often have P/S of 10x or more because they have low marginal costs and high growth potential.^[5] Generally, a P/S below 1.0x is often seen as a potential undervaluation signal,^[5] but only if the company has stable revenue and isn’t drowning in debt. For instance, a retailer with a P/S of 0.5x might mean the market expects its revenue to decline or its margins to stay razor-thin.

A high P/S is only justified if it’s backed by high growth.^[11] When you see a stock with a very high P/S, first check whether its revenue growth rate, gross margin, and market opportunity can support that premium.^[11] For example, a SaaS company with a P/S of 20x might be reasonable if its revenue is doubling every year. But if revenue is only growing 10%, a 20x P/S is way too expensive. For reference, the S&P 500 currently has a P/S of about 3.7x, above its long-term historical average of about 2.51x, suggesting the overall market is somewhat overvalued.^[12] You can compare individual stocks to this benchmark, but remember that industry differences matter.

Who Invented the P/S Ratio and How Should You Use It Properly?

The P/S valuation method was systematically popularized by renowned fund manager Kenneth Fisher in his 1984 book Super Stocks.^[9] He found that sales revenue is more stable and less prone to accounting manipulation than profits, making P/S a more reliable valuation anchor than P/E, especially for evaluating tech companies that were experiencing profit declines or losses at the time.^[9] Fisher argued that profits can be adjusted through accounting tricks like depreciation, amortization, and one-time charges, but revenue is harder to fake, so P/S gives a truer picture of a company’s size.

But Fisher himself acknowledged P/S’s flaws, so in practice he paired it with metrics like the debt-to-equity ratio (requiring it to be no higher than 40%) when selecting stocks.^[10] So the right way to use P/S is: use it as a first-pass screen to find companies with P/S below the industry average, then cross-check with gross margin, net margin, debt ratio, and revenue growth. Never make a decision based on P/S alone. Remember, P/S is a tool, not a holy grail.