Price-to-Book (PB) Ratio: Meaning, Formula, and Example

What Is the Price-to-Book (P/B) Ratio?

Many investors use the price-to-book ratio (P/B ratio) to compare a firm's market capitalization to its book value and locate undervalued companies. This ratio is calculated by dividing the company's current stock price per share by its book value per share (BVPS).

Formula and Calculation of the Price-to-Book (P/B) Ratio

The formula for the price-to-book ratio is:

$P/B ~Ratio = \dfrac{Market~Price~per~Share}{Book~Value~per~Share}$P/B Ratio=Book Value per ShareMarket Price per Share​

Where:

• Market Price per Share = Current market price of the share
• Book Value per Share = (Total assets - intangible assets - total liabilities) ÷ number of outstanding shares

Market value per share is obtained by looking at the information available on most stock tracking websites. You need to find the company's balance sheet to obtain total assets, total liabilities, and outstanding shares. Most investment websites display this financial report under a "financials" tab—some show it on a stock's summary tab.

What the Price-to-Book Ratio Can Tell You

The P/B ratio reflects the value that market participants attach to a company's equity relative to the book value of its equity. Many investors use the P/B ratio to find undervalued stocks. By purchasing an undervalued stock, they hope to be rewarded when the market realizes the stock is undervalued and returns its price to where it should be—according to the investor's analysis.

Some investors believe that the P/B ratio is a forward-looking metric that reflects a company's future cash flows; however, when you look at the information used to calculate the P/B ratio, the factors used are the price investors are willing to pay currently, the number of shares issued by a company, and values from a balance sheet that reflect data from the past. Thus, the ratio isn't forward-looking and doesn't predict or indicate future cash flows.

The P/B ratio also provides a valuable reality check for investors seeking growth at a reasonable price. It is often evaluated with return on equity (ROE), a reliable growth indicator. Large discrepancies between the P/B ratio and ROE often raise a red flag for investors. 

A high P/B ratio suggests a stock could be overvalued, while a lower P/B ratio could mean the stock is undervalued.

As with most ratios, the P/B ratio varies by industry. A company should be compared with similarly structured companies in similar industries; otherwise, the comparison results could be misleading.

P/B Ratios and Public Companies

It is difficult to pinpoint a specific numeric value of a "good" price-to-book (P/B) ratio when determining if a stock is undervalued and therefore, a good investment. It's helpful to identify some general parameters or a range for P/B value, then consider various other factors and valuation measures that more accurately interpret the P/B value and forecast a company's potential for growth.

The P/B ratio has been favored by value investors for decades and is widely used by market analysts. Traditionally, any value under 1.0 is considered desirable for value investors, indicating an undervalued stock may have been identified. However, some value investors may often consider stocks with a less stringent P/B value of less than 3.0 as their benchmark.

Equity Market Value vs. Book Value

Due to accounting procedures, the market value of equity is typically higher than a security's book value, resulting in a P/B ratio above 1.0. During times of low earnings, a company's P/B ratio can dive below a value of 1.0.

For example, in most cases, companies must expense research and development costs, reducing book value because this includes the expenses on the balance sheet. However, these R&D outlays can create unique production processes for a company or result in new patents that can bring royalty revenues. While accounting principles favor a conservative approach in capitalizing costs, market participants may raise the stock price because of such R&D efforts, resulting in wide differences between the market and book values of equity.

Example of How to Use the P/B Ratio

Assume that a company has $100 million in assets on the balance sheet, no intangibles, and $75 million in liabilities. Therefore, the book value of that company would be calculated as $25 million ($100M - $75M).

If there are 10 million shares outstanding, each share would represent $2.50 of book value. Therefore, if the share price is $5, the P/B ratio would be 2.0 (5 / 2.50).

This illustrates that the market price is valued at twice its book value, which may or may not indicate overvaluation. This would depend on how P/B ratios compare against other similarly sized companies in the same sector.

Price-to-Book Ratio vs. Price-to-Tangible-Book Ratio

Closely related to the P/B ratio is the price-to-tangible-book value ratio (PTVB). The latter is a valuation ratio expressing the price of a security compared to its hard (or tangible) book value as reported in the company's balance sheet. The tangible book value number is equal to the company's total book value less than the value of any intangible assets.

Intangible assets can be items such as patents, intellectual property, and goodwill. This may be a more useful valuation measure when valuing something like a patent in different ways or if it is difficult to put a value on such an intangible asset in the first place.

Limitations of Using the P/B Ratio

Investors find the P/B ratio useful because the book value of equity provides a relatively stable and intuitive metric they can easily compare to the market price. The P/B ratio can also be used for firms with positive book values and negative earnings since negative earnings render price-to-earnings ratios useless. There are fewer companies with negative book values than companies with negative earnings.

However, when accounting standards applied by firms vary, P/B ratios may not be comparable, especially for companies from different countries. Additionally, P/B ratios can be less useful for service and information technology companies with little tangible assets on their balance sheets. Finally, the book value can become negative because of a long series of negative earnings, making the P/B ratio useless for relative valuation.

Other potential problems in using the P/B ratio stem from the fact that any number of scenarios, such as recent acquisitions, recent write-offs, or share buybacks can distort the book value figure in the equation. When searching for undervalued stocks, investors should consider multiple valuation measures to complement the P/B ratio.

The Bottom Line

The price-to-book (P/B) ratio considers how a stock is priced relative to the book value of its assets. If the P/B is under 1.0, then the market is thought to be underpricing the stock since the accounting value of its assets, if sold, would be greater than the market price of the shares. Therefore, value investors typically look for companies that have low price-to-book ratios, among other metrics. A high P/B ratio can also help investors identify and avoid overvalued companies.