Price-to-Book (P/B): why I am wary of this ratio

2026-07-16 · By Lubin Danilo, founder of Lubin Investment

The Price-to-Book (P/B) ratio compares a stock's price to its book value, the shareholders' equity on the balance sheet. A low ratio can look like a bargain, but it ignores whether the company earns a decent return on that capital, and it becomes meaningless for companies that buy back stock aggressively. Here is why I almost always prefer free cash flow instead.

What is the Price-to-Book ratio?

The Price-to-Book (P/B) ratio compares two things: what the market pays for a stock, and the company's book value, meaning its shareholders' equity as recorded on the balance sheet (roughly, everything the company owns minus everything it owes). A P/B of 1 means the stock trades at exactly the amount of book equity per share. A P/B of 0.5 means the market values the company at half its book value. It is one of the oldest ratios used in investing, popularized by Benjamin Graham in the 1930s, Warren Buffett's mentor, who looked for stocks trading below their book value as a margin of safety.

The original idea is appealing: buy a stock at a P/B of 0.5 and you are theoretically paying 50 cents for each dollar of net assets the company owns. Even in a liquidation, you should get back more than you paid. This reasoning worked very well for decades, on industries heavy in tangible assets: factories, machinery, real estate, inventory.

How to calculate it, with a real example

The calculation is simple: P/B = market capitalization divided by shareholders' equity, or, per share, share price divided by book value per share. Take an imaginary but representative company: it has 10 billion euros of book equity and 100 million shares outstanding, meaning a book value of 100 euros per share. If the stock trades at 70 euros, its P/B is 0.7: the market values it 30% below book value. If it trades at 150 euros, its P/B is 1.5: the market pays 50% more than what the balance sheet shows.

So far, nothing strange. The problem starts when you try to use this number alone to decide whether a stock is cheap or expensive, without asking the next question: does this company earn a decent return on that capital?

Trap number one: a low P/B says nothing about the return on capital

A real and recent example illustrates this trap well: Citigroup, the large American bank. In 2022, Citigroup traded at roughly half its book value (P/B around 0.5). On paper, that looked like a steal: paying 50 cents for a dollar of bank equity. Except the market had a good reason to punish it at that level: return on tangible common equity (ROTCE, the measure of profit a bank actually earns on each dollar of capital it deploys) sat around 9%, well below rivals JPMorgan or Bank of America. Capital that earns little is structurally worth less than its book value, exactly like a savings account paying 1% is worth less than one paying 5% for the same deposited capital.

Since then, Citigroup went through years of restructuring, sold off low return businesses, cut costs. The result: in the first quarter of 2026, its ROTCE climbed back to 13.1%, a clear improvement. And the stock's P/B followed, rising to around 1.1 to 1.15 times book value, trading above its balance sheet today, versus half of it four years earlier. The P/B ratio was never the useful signal here: the return on capital explained everything, in both directions. A low P/B without knowing whether the return on capital is good or bad is deciding blind.

Trap number two: buybacks can make the ratio absurd

The second trap is even more radical: some excellent companies have negative book value, which makes P/B literally impossible to compute normally. Take Booking Holdings, the parent company of Booking.com: at the end of 2025, its shareholders' equity was negative 5.578 billion dollars, worse than negative 4.02 billion at the end of 2024. Yet Booking remains one of the top rated companies in my quality filter, with 5.4 billion dollars of net income in 2025 and a 20.1% net margin.

How can such a profitable company have negative equity? Through buybacks. When a company repurchases its own shares aggressively (Booking spent 6.4 billion dollars on buybacks in 2025 alone), it mechanically shrinks book equity on the balance sheet, without saying anything negative about its financial health. It is often the opposite signal: a company generating more cash than it needs to reinvest, choosing to return it to remaining shareholders by shrinking the share count. For this type of company, P/B is not just unreliable, it is mathematically unusable.

Why my method almost always prefers P/FCF

For these two reasons, my method almost always relies on P/FCF (price-to-free-cash-flow, the share price divided by the cash a company actually generates each year) rather than P/B. P/FCF directly measures the cash a business produces, independent of how its accounting balance sheet was shaped by decades of acquisitions, asset write-downs, or buybacks. Two companies generating the exact same cash can have radically different balance sheets depending on their history, something I go into more detail on in my article on share buybacks.

This flaw is especially pronounced for software, services, or digital platform companies: their value lies in their brand, algorithms, and customer contracts, intangible assets that accounting almost never values properly on the balance sheet, when it values them at all. A company can be worth tens of billions of dollars on the stock market for a few hundred million dollars of book equity, without that being a bubble: P/B was simply never designed for this type of business model.

P/B is not useless everywhere: the case of banks and insurers

There is one important exception where P/B keeps real meaning: banks and insurers. Their balance sheet is almost entirely made of financial assets (loans, bonds, cash) whose book value is closer to real economic value than a factory depreciated over twenty years. That is why bank investors still track P/B, provided they always pair it with the return on capital (ROE or ROTCE), exactly as in the Citigroup example above. A low P/B combined with an improving return on capital is a far stronger signal than a low P/B alone.

How I actually use this ratio

In my method, I prioritize P/FCF to judge whether a stock is cheap or expensive, because it works for nearly every business model, from banks to software. I do not fully reject P/B: I keep it in mind for financial sector stocks, always paired with the return on capital, never alone. And I am strongly wary of it, or ignore it outright, for any company with heavy buyback activity or mostly intangible assets, where it can literally mean nothing. This is exactly the kind of nuance I wanted to be able to apply in seconds to any stock, which pushed me to build my analysis tool around P/FCF rather than book value.

Price-to-Book (P/B) compares a stock's price to its book equity; a P/B of 0.5 means the market pays half of book value.
Trap 1: a low P/B without checking the return on capital says nothing. Citigroup traded at 0.5 times book value in 2022 (ROTCE around 9%) and around 1.1 to 1.15 times in 2026, after ROTCE climbed to 13.1%.
Trap 2: aggressive buybacks can push book equity negative, as at Booking Holdings (negative 5.578 billion dollars at end of 2025), without that being a sign of weakness: P/B becomes unusable.
My method prefers P/FCF (price over cash generated), which works across business models, including asset-light or heavily repurchased companies.
P/B keeps real meaning for banks and insurers, provided it is always paired with the return on capital (ROE, ROTCE), never used alone.

FAQ

How do you calculate a stock's Price-to-Book (P/B) ratio?

P/B equals market capitalization divided by shareholders' equity, or share price divided by book value per share. A P/B of 1 means the stock trades at exactly the balance sheet's equity per share.

Is a P/B below 1 always a bargain?

No. A low P/B can simply reflect a weak return on capital, as with Citigroup in 2022 (P/B around 0.5, ROTCE around 9%). Always check the return on capital before concluding a stock is undervalued.

Why do some companies have negative shareholders' equity?

Usually because of large, repeated share buybacks, which mechanically shrink book equity without reflecting financial weakness. Booking Holdings, highly profitable, had negative equity of 5.578 billion dollars at the end of 2025.

Is P/FCF always better than P/B?

For the vast majority of companies, yes, because it measures actual cash generated rather than a historical accounting value. P/B still matters for banks and insurers, provided it is always paired with the return on capital.

Is P/B useful for analyzing a bank?

Yes, more than for most sectors, because a bank's balance sheet is almost entirely financial assets close to their real economic value. But it must always be read together with the return on capital (ROE, ROTCE), never alone.

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About the author

Written by Lubin Danilo, founder of Lubin Investment. A self-taught individual investor, I find fundamental analysis fascinating, and it has delivered excellent results. For three years now, my performance has beaten the S&P 500. But analyzing every stock took too much time: sites with incomplete data, calculation methods and criteria never aligned with mine. And spotting the best stocks was just as time-consuming, even with my own well-defined checklist. So I put my software development background to work to build this software, base my investment strategy on its results, and share it with people who share the same passion as me. It judges a company's quality and its price separately, using criteria drawn from the financial literature (Warren Buffett, Michael Mauboussin, Aswath Damodaran).