Price to book ratio: definition, formula and backtest

Last updated: March 2026

The price to book ratio (P/B ratio) is one of the most widely used fundamental indicators in financial analysis and stock valuation. It allows investors to compare a company's market value to its book value — and, according to our 20-year backtest, it provides a measurable edge when selecting stocks in Switzerland and France.

Price to book ratio: definition and importance

The price to book ratio, also known as the price-to-book value ratio or P/BV, represents the relationship between a company's market capitalisation and its book value (shareholders' equity).

This ratio matters because it helps assess whether a stock is overvalued or undervalued relative to its net assets. A P/B below 1 means the stock is trading below its book value — a signal that value investors watch closely.

Investors frequently use this indicator to identify investment opportunities, particularly in industrial or financial sectors where tangible assets play a central role.

How to calculate the P/B ratio

To calculate the P/B ratio, divide the share price by the book value per share. Book value per share is obtained by dividing total shareholders' equity by the number of shares outstanding.

The formula is:

P/B = Share price ÷ (Shareholders' equity ÷ Shares outstanding)

Equivalently: P/B = Market capitalisation ÷ Total shareholders' equity.

Practical example: a company with CHF 500 million in equity, 100 million shares outstanding (book value per share: CHF 5), and a share price of CHF 12, has a P/B of 2.4.

Interpreting the ratio: high and low values

A high P/B (above 3) generally suggests that the market strongly values the company's growth prospects or its ability to generate profits well above its book value.

Conversely, a low ratio (below 1) may indicate either potential undervaluation or structural problems requiring deeper analysis. It can also reflect a distressed sector or persistently low return on equity.

Interpretation must always account for sector context. Technology companies traditionally display high P/B ratios due to the intangible nature of their assets. Banks and insurers often operate with P/B ratios near or below 1, without this necessarily being a warning sign.

Advantages and limitations of the price to book in stock markets

The main advantage of the P/B lies in its simplicity and ability to quickly signal relative valuation. It also has a notable edge over the price-to-earnings ratio (PER): it remains usable even when a company posts losses, whereas the PER becomes meaningless in that scenario.

Some companies resort to creative accounting to flatter their balance sheets — overstating assets or understating liabilities. These practices distort the P/B and make certain book values unreliable.

In the digital economy, technology companies often trade at valuations far above their book value due to intangible assets (intellectual capital, brands, IP). A high P/B can be justified — but it can also signal correction risk if growth expectations fail to materialise.

The P/B during a technology bubble

The years 2024-2025 illustrate perfectly the limits of the price to book in a market driven by artificial intelligence euphoria. Companies like Palantir trade at 84 times their book value and 646 times their earnings — levels historically associated with speculative bubbles. In this environment, investors using P/B as a selection criterion may underperform for several quarters, or even years.

This is not new. During the 1999-2000 internet bubble, value strategies based on P/B also suffered against valuations disconnected from any accounting reality. Disciplined investors who maintained their approach were ultimately rewarded during the 2000-2002 crash and throughout the following decade.

The P/B remains a reliable long-term valuation anchor. When euphoria subsides and markets return to more rational fundamentals, low P/B stocks generally offer significant downside protection and outperformance opportunities. The value investor must accept these periods of relative underperformance as the cost of a strategy that works over time — as our 20-year backtest demonstrates.

Backtest

To evaluate the effectiveness of this ratio on Swiss and French markets, I conducted a backtest covering 2004 to 2024. Stocks were ranked by P/B and divided into quintiles. I used book value data from the most recent half-year period. The process was repeated annually throughout the observation period, enabling performance analysis for each quintile.

Results were adjusted to account for dividends, fractional shares and other corporate events likely to influence stock values.

The P/B performed slightly better within the global market for France, and within economic sectors for Switzerland. I present below only the results obtained with the best method for each market.

Backtest results (average annual performance in CHF)

• Switzerland, best quintile (comparison within economic sectors): 9.04% (market: 8.36%)
• France, best quintile (global market): 4.52% (market: 3.06%)

By company size

Whether in Switzerland or France, segmentation by company size does not work particularly well for this indicator.

Key takeaways from the backtest

• The P/B works on both analysed markets: the top-ranked stocks beat the market.
• Even though absolute returns are lower in France (a market that lagged Switzerland over the period), the P/B adds relatively more value there.

Gross margin growth (comparison within industries) remains the single best-performing ratio studied to date in Switzerland, at 13.4% per year for the top quintile. Net margin is another complementary profitability indicator worth examining alongside the P/B. In France, dividend yield (within industries) still performs best across the overall market, at 7% per year. Investors building a systematic factor strategy may also find relevant context in the 20% stop loss rule article, which addresses the downside management side of a quantitative approach.

Frequently asked questions about the price to book ratio

What is a good P/B ratio?

There is no universal value. A P/B below 1 suggests potential undervaluation, but this depends heavily on the sector and the company's financial health. Banks and industrial companies often display P/B ratios between 0.8 and 1.5, while technology companies can legitimately exceed 5 due to their intangible assets.

Can you rely solely on the P/B to invest?

No. Our backtest shows the P/B works, but other ratios outperform it depending on the market. In Switzerland, gross margin growth generates 13.4% per year versus 9.04% for the P/B. In France, dividend yield reaches 7% per year. Combining multiple indicators improves the robustness of your strategy.

Does the P/B work for all companies?

Not really. The P/B is most relevant for companies with significant tangible assets (industry, finance). It is less reliable for technology or service companies, where value resides primarily in unrecorded intangible assets. That said, opportunities can emerge in any sector.

What is the difference between P/B and PER?

The PER (price-to-earnings ratio) compares the share price to profitability (earnings), while the P/B compares it to net assets (equity). The P/B's key advantage: it remains usable even when the company is loss-making, which the PER does not allow. The PER, however, is more directly linked to future earnings capacity.

How do you use the P/B in a practical investment strategy?

The most effective approach is to use the P/B alongside other ratios, comparing companies within the same sector rather than across the whole market. Our backtest shows this sector-based method delivers better results in Switzerland. It is also advisable to verify that a low P/B reflects genuine undervaluation rather than deteriorating equity (accumulated losses, excessive debt).

Conclusion

Despite declining popularity in the era of intangible assets, the price to book ratio remains a valuable tool in financial analysis. It offers investors a measurable outperformance opportunity, even if this advantage remains relatively modest over the period studied.

In the digital age, book value has arguably lost some of its relevance for valuing certain companies. However, cyclical trends are worth watching: in a few years, tangible assets could regain their place at the heart of investor concerns — and the P/B become a particularly effective filter once again.

Sources and data

Financial data: FactSet. Proprietary backtest on Swiss (MSCI Switzerland) and French (Euronext Paris) market data, 2004-2024 period, adjusted for dividends and corporate events.