Castle BiosciencesCSTL -0.97%73 PB Ratio is 1.61 as of Jul. 02, 2026, which is 9% below its 10-year median of 1.77. GuruFocus rates CSTL with a GF Score™ of 73/100 and a GF Value™ of $29.18 (Modestly Undervalued). The stock has 4 warning signs investors should review. Among 195 Medical Diagnostics & Research companies, Castle Biosciences ranks better than 65.13% on this metric.
The historical rank and industry rank for Castle Biosciences's PB Ratio or its related term are showing as below:
CSTL'
s PB Ratio Range Over the Past 10 Years
Min: 0.86 Med: 1.77 Max: 8.5
Current: 1.61
During the past 9 years, Castle Biosciences's highest PB Ratio was 8.50. The lowest was 0.86. And the median was 1.77.
CSTL's PB Ratio is ranked better than 65.13% of 195
companies
in the Medical Diagnostics & Research industry
Industry Median: 2.01
vs CSTL: 1.61
During the past 12 months, Castle Biosciences's average Book Value Per Share Growth Rate was -0.20% per year.
During the past 3 years, the average Book Value Per Share Growth Rate was 1.80% per year.
During the past 5 years, the average Book Value Per Share Growth Rate was -1.00% per year.
During the past 9 years, the highest 3-Year average Book Value Per Share Growth Rate of Castle Biosciences was 44.60% per year. The lowest was -5.20% per year. And the median was 0.65% per year.
Back to Basics: PB Ratio
Castle Biosciences (NAS:CSTL) PB Ratio Explanation
The PB Ratio works the best for the businesses that earn most of their profit from their assets, e.g. banks and insurance companies.
Be Aware
Some businesses have very light assets, such as software companies or insurance agencies. The PB Ratio does not work well for these companies. Some companies even have negative equity, so the PB Ratio cannot be applied to them.
Castle Biosciences PB Ratio Related Terms
Castle Biosciences PB Ratio Historical Data
* Premium members only.
The historical data trend for Castle Biosciences's PB Ratio can be seen below:
* For Operating Data section: All numbers are indicated by the unit behind each term and all currency related amount are in USD. * For other sections: All numbers are in millions except for per share data, ratio, and percentage. All currency related amount are indicated in the company's associated stock exchange currency.
For the Diagnostics & Research subindustry, Castle Biosciences's PB Ratio, along with its competitors' market caps and PB Ratio data, can be viewed below:
* Competitive companies are chosen from companies within the same industry, with headquarter located in same country, with closest market capitalization; x-axis shows the market cap, and y-axis shows the term value; the bigger the dot, the larger the market cap. Note that "N/A" values will not show up in the chart.
Castle Biosciences PB Ratio vs Medical Diagnostics & Research Industry
For the Medical Diagnostics & Research industry and Healthcare sector, Castle Biosciences's PB Ratio distribution charts can be found below:
* The bar in red indicates where Castle Biosciences's PB Ratio falls into.
The PB Ratio, or Price-to-Book ratio, or Price/Book, is a financial ratio used to compare a company's market price to its Book Value per Share. It is a ratio widely used to value stocks.
* For Operating Data section: All numbers are indicated by the unit behind each term and all currency related amount are in USD. * For other sections: All numbers are in millions except for per share data, ratio, and percentage. All currency related amount are indicated in the company's associated stock exchange currency.
It can also be calculated from the numbers for the whole company:
A closely related ratio is called Price-to-Tangible-Book. The difference between Price-to-Tangible-Book and PB Ratio is that book value other than intangibles are used in the calculation.
Castle Biosciences (CSTL) has a PB Ratio of 1.61 as of Jul. 02, 2026. Price-to-Book ratio is the ratio of share price to a company's book value per share. View historical data on Castle Biosciences and its competitors. This is near median its historical median of 1.77. Over the past decade, Castle Biosciences' PB Ratio has ranged from 0.86 to 8.50. According to the industry distribution chart, Castle Biosciences ranks #68 out of 195 companies in the Medical Diagnostics & Research industry, placing it in the top 34.9%.
Is Castle Biosciences' PB Ratio too high?
Castle Biosciences' current PB Ratio of 1.61 is near median its 10-year median of 1.77. Over the past 10 years, this metric has ranged from a low of 0.86 to a high of 8.50. The Medical Diagnostics & Research industry median PB Ratio is 2.01. Castle Biosciences' value of 1.61 is 19.9% below this industry median. Based on the distribution chart, Castle Biosciences ranks #68 out of 195 companies in the Medical Diagnostics & Research industry, which is above the industry midpoint. Overall, Castle Biosciences has a GF Score™ of 73/100 and is considered Modestly Undervalued, reflecting its overall financial health beyond just this single metric.
How does Castle Biosciences' PB Ratio compare to FLGT and MYGN?
According to the Medical Diagnostics & Research industry distribution chart, Castle Biosciences ranks #68 out of 195 companies for PB Ratio. This puts Castle Biosciences in the upper half of its industry. The industry median PB Ratio is 2.01. Castle Biosciences' value of 1.61 is 19.9% below this benchmark. Historically, Castle Biosciences' own PB Ratio has ranged from 0.86 to 8.50 over the past decade. While the company's 10-year median is 1.77 vs. the industry median of 2.01, Castle Biosciences has consistently been below the industry average. See the competitive comparison table and distribution chart on this page for a detailed peer-by-peer breakdown.
What is a good PB Ratio for a Medical Diagnostics & Research company?
The median PB Ratio among Medical Diagnostics & Research companies is 2.01, based on 195 companies in the industry. Companies in the top quartile (top 25%) have a PB Ratio significantly above this median, while those in the bottom quartile fall well below. However, PB Ratio should not be evaluated in isolation — investors should consider it alongside profitability, growth, and financial strength metrics. Castle Biosciences's current PB Ratio of 1.61 is 19.9% below the industry median. Use the industry distribution chart on this page to see where any company falls relative to its peers.
What does a high PB Ratio mean?
A high PB Ratio can signal that a stock is expensive relative to its fundamentals. Price-to-Book ratio is the ratio of share price to a company's book value per share. View historical data on Castle Biosciences and its competitors. For the Medical Diagnostics & Research industry, the median PB Ratio is 2.01 — values significantly above this may indicate overvaluation, while values below may suggest a bargain or underlying issues. Castle Biosciences's current PB Ratio is 1.61, which is near median its own 10-year median of 1.77. However, context matters — high-growth companies often justify higher valuations. Always evaluate alongside other metrics like GF Score™ and GF Value™.
Is Castle Biosciences stock overvalued right now?
Based on GuruFocus' analysis, Castle Biosciences (CSTL) is currently considered Modestly Undervalued. The stock's GF Value™ is $29.18, compared to a current price of $24.48 — trading 16.1% below its estimated fair value. The current PB Ratio is 1.61, which is near median its 10-year median of 1.77 and 19.9% below the Medical Diagnostics & Research industry median of 2.01. Castle Biosciences' overall GF Score™ is 73/100 with 4 warning signs to review. Investors should evaluate multiple metrics — including profitability, growth, and financial strength — before making a decision.
How is PB Ratio calculated?
PB Ratio is calculated from a company's financial statements. For Castle Biosciences (CSTL), the current PB Ratio is 1.61 as of Jul. 02, 2026. GuruFocus calculates this using data sourced from SEC filings and annual reports. See the calculation section and 30-year financial data on this page for the full breakdown.
Is Castle Biosciences (CSTL) Overvalued in 2026?
Based on GuruFocus' analysis, Castle Biosciences stock appears to be undervalued.
The current stock price of $24.48 is trading 16.1% below its estimated GF Value™ of $29.18.
GuruFocus considers Castle Biosciences to be Modestly Undervalued.
Key valuation signals for CSTL:
PB Ratio: 1.61 (near median its 10-year median of 1.77)
GF Value™: $29.18 vs. price of $24.48 (16.1% below fair value)
Industry Position: 19.9% below the Medical Diagnostics & Research median (#68 of 195)
No single metric tells the full story. See the CSTL stock analysis page for a complete view including 30-year financials, guru trades, and insider activity.
Castle Biosciences Inc is a molecular diagnostics company. The group provides test solutions for the diagnosis and treatment of dermatologic cancers, Barrett's esophagus (BE), and uveal melanoma. The product portfolio of the company includes DecisionDx-Melanoma, a risk stratification gene expression profile (GEP) test; DecisionDx-SCC, a risk stratification test for cutaneous squamous cell carcinoma; MyPath Melanoma, a diagnostic GEP test for use in patients with difficult-to-diagnose melanocytic lesions; and TissueCypher, a test to predict future development of progression of high-grade dysplasia and/or esophageal cancer. The company derives revenues through the delivery of test reports for its molecular diagnostic tests.
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