The price-to-book ratio compares a company’s share price with the value of its net assets, as recorded on its balance sheet. It is one of the oldest valuation measures in investing and remains especially important for banks, insurers and other businesses whose value is closely tied to what they own. Understanding it helps explain why some shares look cheap for years and why others trade at many times their book value.
What book value means
Book value is what would theoretically be left for shareholders if a company sold all its assets and paid off all its debts at the values shown in its accounts. In simple terms, it is total assets minus total liabilities, also known as shareholders’ equity.
Divide that figure by the number of shares, and you get book value per share. The price-to-book ratio, often shortened to P/B, is the share price divided by book value per share.
If a share trades at 200p and its book value per share is 100p, the P/B ratio is 2. Investors are paying twice the accounting value of the company’s net assets.
How to read the number
A P/B ratio below 1 means the market values the company at less than its net assets. That can look like a bargain, and sometimes it is. More often, it signals that investors doubt the assets are worth what the accounts say, or expect the company to earn poor returns on them.
A P/B ratio well above 1 means investors expect the company to generate strong returns from its assets, or believe it has valuable things the balance sheet does not capture fully, such as brands, software, patents or customer relationships.
Why it matters so much for banks
For banks, the balance sheet is the business. Loans, bonds and deposits make up most of the assets and liabilities, and they are valued closer to market prices than the factories or brands of an industrial company. That makes book value a more meaningful anchor.
Bank investors often look at tangible book value, which strips out intangible items such as goodwill from past acquisitions. They then compare the P/B ratio with the bank’s return on equity. As a rule of thumb, a bank that earns a return on equity above its cost of capital deserves to trade above book value, while one that earns less often trades below it. This is why changes in the outlook for profits, including the loan loss provisions banks set aside, can move their valuations significantly.
UK banks spent many years after the financial crisis trading below book value, reflecting weak returns and doubts about asset quality.
Where the ratio is less useful
For many modern companies, book value says very little. A software business or a consumer brand may have most of its value in things that do not appear on the balance sheet at all. Its P/B ratio may look extremely high, but that does not necessarily make it expensive. Comparing a technology company’s P/B with a bank’s makes little sense.
Accounting choices can also distort book value. Share buybacks reduce equity, which can push the ratio up. Large write-downs can push it down. Our guide to share buybacks explains why companies use them and how they affect the numbers.
Comparing P/B with other measures
The P/B ratio works best alongside other measures. The price-to-earnings ratio shows how much investors pay for each pound of profit. Dividend yield shows the income return. Return on equity shows how well a company uses its assets. None is enough on its own.
It also makes sense to compare a company with its peers and its own history rather than with the market as a whole. A bank trading at 0.8 times book when its peers trade at 1.2 deserves a closer look, but the question is always why.
Common mistakes
The biggest mistake is treating a low P/B ratio as automatically cheap. Shares can trade below book value for good reasons, and stay there for years. The market may be right that the assets are overstated or the returns too low. This is often called a value trap.
The second mistake is applying the same yardstick to every sector. P/B is a powerful tool for financials and asset-heavy businesses, and a weak one for companies whose value lies in ideas and intangibles.
Bringing it together
The price-to-book ratio compares a company’s market value with its net assets. It is especially useful for banks and insurers, where book value is closely linked to the business, and much less useful for asset-light companies. Read it alongside returns, earnings and peers, and always ask why a share trades where it does.
If you would like to understand how your grasp of company valuation and wider market skills compares with what consistent trading requires, our free trader assessment is a useful place to begin.
