Castle Biosciences Inc (CSTL) stock analysis
Close on Nov 12, 2026Market cap $1.05BP/E –Yield 0.00%
StockData Score
Prices as of Nov 11, 2026How the score works
Mixed11 of 30 checks passed
Castle Biosciences passes 11 of the 30 checks behind our score; 11 could not be run for lack of data and count as not passed. Each dot in the shape is one check — hover it for the numbers.
- Valuation
- 2/6
- Growth
- 2/6
- Past performance
- 3/6
- Financial health
- 4/6
- Dividend
- 0/6
What stands out
Trading below fair value
The share price of $33.99 is below our fair value estimate of $36.69.
Low debt
Debt is 2.1% of shareholders' equity, under the 40% we consider low.
Revenue growing 10%+ a year
Revenue grew 35.9% a year over the last three fiscal years.
Debt covered by cash flow
Operating cash flow over the last twelve months equals 394% of total debt.
What to watch
Margin of safety under 20%
The price is 7.4% below fair value, less than the 20% cushion we look for.
Return on equity under 15%
Return on equity was -4.9% over the last twelve months and averaged -7.9% over five years; we look for 15% on both.
Return on capital under 10%
Return on invested capital was -11.1%, below the 10% that usually covers the cost of capital.
Interest not well covered
Operating income covers interest expense -51.2 times; we look for at least 5.
Valuation2/6
P/E against its history
Not enough price and earnings history to compare.
P/E against the industry
Needs positive earnings and enough profitable companies in the industry.
EV/EBITDA against its history
Needs positive EBITDA and price history.
P/B below the industry
Castle Biosciences's price-to-book of 2.17 is below the Health Services median of 3.40.
Trading below fair value
The share price of $33.99 is below our fair value estimate of $36.69.
Margin of safety under 20%
The price is 7.4% below fair value, less than the 20% cushion we look for.
Growth2/6
Revenue growing 10%+ a year
Revenue grew 35.9% a year over the last three fiscal years.
EPS growth over 3 years
Needs positive EPS three years ago and today.
Earnings acceleration
Needs positive net income now, a year ago and five years ago.
Growing slower than the industry
Revenue grew 9.8% over the last twelve months; the Health Services median is 16.9%.
Guidance raised
Castle Biosciences raised its 2026 total revenue outlook on Jul 30, 2026.
Gross margin slipping
Gross margin was 77.1% over the last twelve months, against 79.9% a year earlier.
Past performance3/6
Return on equity under 15%
Return on equity was -4.9% over the last twelve months and averaged -7.9% over five years; we look for 15% on both.
Return on capital under 10%
Return on invested capital was -11.1%, below the 10% that usually covers the cost of capital.
Return on equity above the industry
Castle Biosciences's return on equity of -4.9% is above the Health Services median of -9.9%.
Earnings over 5 years
Needs positive net income five years ago and in the latest year.
Net margin above its 5-year average
Net margin was -6.1% over the last twelve months, against a 5-year average of -22.0%.
Net margin above the industry
Castle Biosciences's net margin of -6.1% is above the Health Services median of -10.3%.
Financial health4/6
Low debt
Debt is 2.1% of shareholders' equity, under the 40% we consider low.
Debt rising against equity
Debt to equity rose from 0.0% five years ago to 2.1%.
Debt covered by cash flow
Operating cash flow over the last twelve months equals 394% of total debt.
Interest not well covered
Operating income covers interest expense -51.2 times; we look for at least 5.
Short-term assets cover short-term debts
Current assets are 5.28 times current liabilities.
Low bankruptcy risk
The Altman Z-score is 6.67; above 3 is the safe zone and below 1.8 the distress zone.
Dividend0/6
No dividend
Castle Biosciences has not paid a dividend in the last twelve months.
Yield against Treasuries
No dividend.
Yield against the market
No dividend.
Dividend stability
No dividend.
Earnings cover
No dividend.
Cash-flow cover
No dividend.
Fair value
How we estimate itOur estimate per share
$36.69
The share price is 7% below this estimate.
| Method | Multiple used | Own 5Y median | Industry median | Value per share | Weight |
|---|---|---|---|---|---|
| P/B | 2.5× | 1.6× | 3.4× | $38.83 | 50% |
| P/S | 2.8× | 2.8× | 2.8× | $34.56 | 50% |
| Earnings powerleft out, too far from the others | 11.8% cost of equity | – | – | $5.49 | – |
| Fair value | $36.69 | 100% | |||
Valuation over time
Using the earnings and balance sheet published at each date, not today's.
- EV/EBITDA at month end
- Health Services median 27.9
An estimate from reported numbers and market multiples, not a price target or investment advice. It can be far off for companies whose profits are about to change sharply.
Market risk
From the past year of daily prices.
Liquidity
Medium risk
- Average value traded per day
- $13.79M
- Value traded per 1% price move
- $5.26M
Downside
High risk
- Typical loss in a bad month
- 27.8%
- Volatility (annualized)
- 54%
- Sharpe ratio, 1 year
- -0.12
- Beta to the S&P 500 (5Y)
- 1.38
Typical bad-month loss, week by week
Margins
Share of revenue, fiscal years 2017 to 2025
Gross margin
Operating margin
Net margin
Growth rates
Compound annual growth to fiscal 2025
| Per year | 1 year | 3 years | 5 years | 10 years | Five-year pace |
|---|---|---|---|---|---|
| Revenue | +3.7% | +35.9% | +40.6% | – | |
| Gross profit | +0.5% | +37.5% | +38.8% | – | |
| Free cash flow | -22.5% | – | +40.8% | – |
Returns and balance sheet
9 fiscal years. Hover a measure to see how it is calculated.
| Measure | FY2017 | FY2020 | FY2025 | Trend |
|---|---|---|---|---|
| Return on equity | – | -4.1% | -5.2% | |
| Return on assets | – | -3.7% | -4.4% | |
| Current ratio | – | 20.58 | 5.26 | |
| Debt to equity | – | 0.00 | 0.02 | |
| Net debt to EBITDA | – | 67.52× | 52.32× | |
| Interest coverage | – | -2.5× | -497.8× | |
| Inventory turnover | – | 5.6× | 7.7× | |
| Capex to revenue | – | 7.6% | 10.5% | |
| Diluted shares | – | 19M | 29M |
Where the cash went
Fiscal 2021 to 2025, five years combined
Castle Biosciences generated $195.48M from operations and spent $87.08M on capital expenditure, dividends and share buybacks. 100% of that went back into the business.
DuPont analysis
Return on equity split into margin, efficiency and leverage
| Fiscal year | Net margin | Asset turnover | Equity multiplier | Return on equity |
|---|---|---|---|---|
| FY2025 | -7.0% | 0.62× | 1.20× | -5.2% |
| FY2024 | 5.5% | 0.67× | 1.16× | 4.3% |
| FY2023 | -26.1% | 0.49× | 1.14× | -14.5% |
| FY2022 | -49.0% | 0.30× | 1.12× | -16.6% |
| FY2021 | -33.3% | 0.21× | 1.09× | -7.6% |
| FY2020 | -16.4% | 0.22× | 1.12× | -4.1% |
| FY2019 | 10.2% | 0.73× | 4.98× | 37.0% |
Piotroski F-Score
Nine tests of profitability, balance sheet and efficiency, fiscal 2025 against fiscal 2024
- ProfitableNet income above zero-$24.16M
- Cash generatingOperating cash flow above zero$64.35M
- Return on assets improvedROA up on the prior year4.0% → -4.5%
- Earnings backed by cashOperating cash flow above net income$64.35M vs -$24.16M
- Less leverageLong-term debt to assets fell1.8% → 1.7%
- Better liquidityCurrent ratio rose7.29 → 5.26
- No dilutionShare count did not rise29M → 29M
- Gross margin improvedGross margin up on the prior year81.87% → 79.37%
- More efficientAsset turnover rose0.73 → 0.65
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