The P/B ratio — when do you compare book value correctly?

The P/B ratio — Price-to-Book — is calculated as the share price divided by book value per share (equity per stock), and the comparison is right only when the balance sheet credibly represents the business's real value. For banks, investment companies and other capital-intensive companies, book value is the very raw material of the business — there P/B is a natural yardstick. For knowledge and software companies the value sits in brand, code and employees that never enter the balance sheet, and then P/B becomes a number without interpretability. The art is thus not the arithmetic — it is a division — but knowing when book value carries information and when it is merely an accounting residue.

The formula — two routes to the same number

P/B = Share price ÷ Book value per share (equity per stock)

Equivalent at company level: P/B = Market capitalization ÷ Equity. Book value per share is in turn calculated as (equity − treasury stocks) ÷ number of stocks — stocks held in the company's own hands are a parked asset, not something the owners can meaningfully count as theirs.

Two practice questions: keep the same definition of equity (with or without minority interests) throughout the comparison, and preferably use the balance sheet of the latest quarterly report. Unlike earnings, book value moves slowly — but share buybacks and dividends make a year-old number noticeably wrong for precisely the companies where the buy-and-sell discussion tends to be at its liveliest.

The worked example: an industrial group and a bank

The industrial company. Equity 1 850 Mkr, of which treasury stocks 50 Mkr — adjusted equity 1 800 Mkr. Number of stocks: 72 million. Book value per share = 1 800 ÷ 72 = 25,0 kr. Share price: 50 kr. P/B = 50 ÷ 25,0 = 2,0. The market prices the company at double book value — reasonable if, and only if, the company is moving toward a durable return on equity (ROE) well above what the owners can demand anywhere else.

The bank. Reported equity per stock (book value per share): 95 kr. Share price: 114 kr. P/B = 114 ÷ 95 = 1,2. For a bank, the level 1,0 is a natural anchor: assets are continuously valued near market value and the capital base is regulated. A stable banking business that earns its cost of capital trades around book value, and the deviation upward or downward reflects whether the market believes in a ROE above or below that level. A multiple of 1,2 therefore does not say expensive — it says that the market is pricing a return somewhat above the cost of capital for the foreseeable future.

The link to ROE — why P/B above 1 is normal

Book value is history: paid-in capital plus accumulated earnings minus dividends and share buybacks. The share price is, of course, the future: expected cash flows. A company that durably earns a return on its equity above its cost of capital is reasonably worth more than book — the higher the ROE and the more sustainable it is, the higher the justified P/B. In a standard perpetual growth model, roughly P/B ≈ (ROE − growth rate) ÷ (cost of capital − growth rate): with ROE 18 %, cost of capital 9 % and growth 4 %, a P/B ≈ (18 − 4) ÷ (9 − 4) = 2,8 is justified. That is why P/B and ROE are a pair — V05 and V09 in the AKM1 model are always read together. A P/B of 2,0 with ROE 18 % is a different world from P/B 2,0 with ROE 8 %. And mirrored: P/B below 1,0 does not automatically mean cheap — the market may be pricing upcoming impairments or a business model that systematically destroys capital.

When book value carries the analysis

• Banks and insurance companies. The balance sheet is the business: assets and liabilities continuously valued near market, the capital base regulated. P/B together with ROE is the industry's standard measure — and the net-asset reasoning becomes especially clear when the interest rate environment moves the cost of capital.
• Investment companies. Net asset value is a finely polished book value where the holdings are reported at market value. The relationship between price and net asset value — the discount or the premium, of course — is here the very analysis, not an aid alongside it.
• Capital intensive industry and real estate. Machines, plants and property portfolios dominate the balance sheet. With the proviso that revaluation reserves and depreciation practice can lie years from current market values, book value gives a meaningful floor.

When P/B fails — three classic cases

Case 1: the invisible value. Brands, software and competence built internally are not reported as assets — only acquired intangible assets (goodwill and acquired rights) enter the balance sheet. Two otherwise equivalent companies therefore get different equity depending on whether the growth was built or bought. A knowledge company with P/B 15 is not expensive in the P/B sense — the measure is simply empty there.

Case 2: the shrunk denominator. Large share buybacks press down equity, P/B rises mechanically without anything happening to the business, and in the extreme equity turns negative and the division becomes meaningless. The check: the five-year development of equity, not just the last balance sheet date — the same mechanics that make ROE's denominator deceptive (V09's classic pitfall) strike P/B head-on.

Case 3: accounting choices that splinter comparability. IFRS leaves room for different valuation practices — revaluation reserves, capitalized development, treatment of goodwill — and two companies can report the same real position with different reported equity. Before P/B is compared between two companies: read through the notes to the accounts of what the equity actually consists of.

The industry interpretation — what is normal

Descriptively, with no yardstick beyond the comparison group: well-managed banks have historically moved around 0,8–1,5 times book value, with ROE and the interest rate environment explaining where in the range the multiple lands. Investment companies often trade at a discount to net asset value — the discount is itself an object of study, since it reflects both credibility in management and the general appetite for risk. Property companies vary sharply with the valuation cycle and the interest rate environment, because the property values in the books move with the market. And knowledge companies — software, services, brand-driven consumption — are regularly quoted at 5–15 times book value or higher, which is not an alarm bell but a sign that the measure is the wrong tool: the value does not sit in the balance sheet. The rule is the same as for ROE (V09): the multiple has no universal zero point, only industry-specific frames of reference.

The exercise: pair P/B with ROE on a real company

1. Fetch equity, treasury stocks and the number of stocks for a company you follow — the balance sheet and the note on equity are enough. 2. Calculate book value per share and today's P/B. 3. Pair with ROE for the three most recent years: does the return legitimize the multiple, or does it rest on leverage and a temporary peak? 4. Enter the numbers in the calculator and compare the placement against the industry's typical level.

Next steps

• Deepen in the course P/B (V05): six chapters — chapter after chapter — on book value analysis, bank comparisons and the pair with ROE.
• See how V05 is placed among the nineteen other variables in the Curriculum — the valuation block is read as a whole.
• Build the context in the portfolio builder: a multiple is one tool among several, never a decision.

FAQ

What is the P/B ratio?

P/B-talet (Price-to-Book) är aktiekursen delat med eget kapital per aktie — ekvivalent börsvärde delat med eget kapital. Det ställer frågan vad marknaden betalar per krona bokfört eget kapital, och i räkneexemplet ger industribolagets kurs på 50 kr och eget kapital på 25,0 kr per aktie P/B = 2,0.

When is the P/B ratio useful?

När balansräkningen på ett trovärdigt sätt speglar verksamhetens verkliga värde: för banker, investmentbolag och kapitaltät industri är P/B ett naturligt standardmått. För kunskaps- och mjukvarubolag sitter värdet i varumärke, kod och medarbetare som aldrig kommer in i balansräkningen — där är måttet tomt.

What does it mean when P/B is above or below 1?

P/B över 1 är normalt för ett bolag som varaktigt avkastar sitt eget kapital (ROE) över kapitalkostnaden — i exemplet motiverar ROE 18 %, kapitalkostnad 9 % och tillväxt 4 % ungefär P/B 2,8. P/B under 1,0 är inte automatiskt billigt: marknaden kan prissätta kommande värdenedskrivningar eller en affärsmodell som förstör kapital — läs därför alltid P/B tillsammans med ROE.

This is educational financial analysis, not investment advice.