What Is a Price-to-Book Ratio? P/B Explained

The price-to-book ratio (P/B) compares a company’s market price to its book value — the net worth of its assets minus liabilities, as recorded on the balance sheet. A P/B of 1 means the market is pricing the company at exactly what its accounting records say it’s worth if everything were liquidated at book value. Above 1, the market expects the company to be worth more than its recorded assets; below 1, the market is pricing it below that floor.

How it’s calculated

The formula is straightforward:

P/B ratio = Market price per share ÷ Book value per share

Book value per share itself comes from the balance sheet: total assets minus total liabilities (shareholders’ equity), divided by shares outstanding. You can also compute it at the company level rather than per share — market capitalization divided by total shareholders’ equity — which gives the same ratio.

A company with $500 million in shareholders’ equity and 50 million shares outstanding has a book value of $10 per share. If the stock trades at $25, its P/B ratio is 2.5 — the market is valuing the company at two and a half times its recorded net worth.

What “book value” actually represents

Book value is an accounting figure, not a market estimate. It reflects historical cost: assets are generally recorded at what the company paid for them (adjusted for depreciation), not their current market value. That distinction matters enormously depending on the kind of business.

For an asset-heavy company — a bank, an insurer, a manufacturer with real estate and equipment — book value tends to be a reasonably meaningful floor, since the balance sheet is dominated by things with observable resale value. For an asset-light company — a software company whose real value sits in its people, code, and brand — book value is nearly meaningless, because the balance sheet doesn’t capture intangibles like a strong customer base or a defensible product moat the way it captures a factory. This is why P/B is used heavily in some sectors (financials especially) and largely ignored in others (software, biotech).

P/B vs P/E: two different lenses

Price-to-book and the more commonly cited price-to-earnings ratio answer different questions, and they’re often used together rather than as substitutes.

	Price-to-book (P/B)	Price-to-earnings (P/E)
Compares price to	Net asset value (balance sheet)	Profit (income statement)
Best suited for	Asset-heavy businesses, financials	Businesses with stable, positive earnings
Breaks down for	Asset-light, intangible-heavy businesses	Unprofitable or highly cyclical businesses
Roughly answers	”What would this be worth if liquidated?"	"How many years of profit am I paying for?”
Sensitive to	Accounting conventions for asset valuation	Accounting conventions for earnings recognition

A company can look cheap on one measure and expensive on the other — a capital-intensive business with thin margins might carry a low P/B but a high P/E, while a high-margin software company is often the reverse. Neither ratio is complete on its own; both are best read alongside the underlying financial statements rather than in isolation.

Why a low P/B isn’t automatically “cheap”

Classic value investing treated a P/B below 1 as a signal of undervaluation — buying assets for less than they’re recorded to be worth. That reasoning still holds in some cases, but it breaks in others, and it’s worth knowing why before treating a low ratio as a buy signal:

• Book value can be stale. Assets recorded decades ago at historical cost may bear no relationship to current replacement cost or market value, in either direction.
• A low P/B can reflect real distress, not a discount. If the market expects a company’s assets to be written down, sold at a loss, or made obsolete, the stock price may be correctly anticipating a lower true book value than what’s currently on the books.
• Intangible-heavy businesses structurally show a high P/B even when fairly valued, because so much of their value — brand, software, network effects — never appears as a balance-sheet asset at all. Comparing a software company’s P/B to a bank’s P/B tells you almost nothing.
• Buybacks and losses both shrink book value mechanically. A company that has been aggressively repurchasing shares or has posted a string of losses will show a smaller equity base and a correspondingly higher P/B, independent of any change in its actual prospects.

Where P/B is still genuinely useful

Despite those caveats, P/B remains a standard tool in a few specific contexts:

• Financial institutions. Banks and insurers hold assets — loans, securities, cash — that are relatively close to their market value, and their earnings can be volatile or cyclical, making P/E a noisier signal. P/B is the default valuation lens for the sector for exactly this reason.
• Screening for distress or turnaround situations, where a P/B near or below 1 flags companies trading close to liquidation value, worth investigating further rather than acting on directly.
• Comparing companies within the same industry, where accounting conventions and asset composition are similar enough that the ratio is measuring like against like, rather than comparing a bank to a software company.

The takeaway

Price-to-book measures how a company’s market price stacks up against its recorded net worth on the balance sheet, and it’s most meaningful for asset-heavy businesses like banks and insurers, where book value tracks something close to real economic value. For asset-light businesses, the ratio is structurally uninformative, since intangibles like software and brand rarely show up on the balance sheet at all. As with any single ratio, it’s a starting screen rather than a verdict — pair it with earnings-based measures like P/E and a look at what’s actually driving the market cap before drawing conclusions from it alone.