CSTL (Castle Biosciences) GF Value Rank: 8 (As of Jul. 11, 2026) — 100% Above Median

What is Castle Biosciences GF Value Rank?

Castle Biosciences CSTL -3.42% 77 GF Value Rank is 8 as of Jul. 11, 2026, which is 100% above its 10-year median of 4.00. GuruFocus rates CSTL with a GF Score™ of 77/100 and a GF Value™ of $29.20 (Modestly Undervalued). The stock has 4 warning signs investors should review.

Castle Biosciences has the GF Value Rank of 8.

GF Value Rank evaluates the exclusive GuruFocus valuation and performance of a stock, rated on a scale from 1 to 10. It is determined by the price-to-GF-Value (P/GF Value) ratio, a proprietary metric calculated based on historical multiples along with an adjustment factor based on a company's past returns and growth and future estimates of the business' performance.

GuruFocus found that for valuation, we cannot simply give stocks a better GF Value rank simply because they have a lower P/GF Value ratio. Backtesting shows that over the long term, the two worst-performing groups are the most expensive group (with the highest P/GF Value ratio) and the least expensive group (with the lowest P/GF Value ratio).

We can understand why the most expensive group underperforms. We were initially puzzled by the underperformance of the least expensive group, but we realized there is a reason why some stocks are super cheap. If they look too undervalued, it is often because the businesses behind them are poor quality. The market realized this and gave them low valuations. In a way, the market is efficient.

After multiple backtesting analyses, we granted the stocks in third-cheapest percentile the highest GF Value rank, as they have performed the best over a full market cycle. Stock performance is actually not as sensitive to valuation as it is to growth and profitability. On average, the companies in the 20%-50% valuation groups have similar performances. Therefore, we should avoid the most expensive and the least expensive stocks. We can be more tolerant of valuation.

A higher score indicates a stock with a relatively low valuation and substantial potential for outperformance. Conversely, a lower score often reflects stocks that are either highly overvalued or deeply undervalued, both of which tend to underperform.

Please click GF Score to see more details on the GF Score's 5 Key Aspects of Analysis.