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Castle Biosciences Inc (CSTL) fair value: what the stock is really worth

As of Sep 23, 2026: fair value of Castle Biosciences Inc $21.45, price $34.88, upside -38.5%, quality 46 out of 100. Calculated from audited financials with 26 valuation models and 37 quality factors, updated daily.

  1. Fair value above price? No
  2. Good quality? No
  3. Add to watchlist

Healthcare · US · ISIN US14843C1053

CB Castle Biosciences Inc logo Thin data Sep 23, 2026

Castle Biosciences Inc

CSTL · US

Weakest SetupStrongly overvalued and low quality.

!Fair value $21.45 · Strongly overvalued (−39%)
!Quality 46/100
!Mixed Growth (revenue 5y +40.6 %/yr)
!Loss-making · -3.8% net margin (TTM)
✓Low debt · generates free cash flow
!Trails peers (1/11)
!Narrow moat 16/100
!Insider activity 44/100
!Evidence only low, so the estimate is less certain
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What runs behind every stock

26 valuation models 8 families, DCF to NCAV 37 quality factors margins, balance sheet, cashflow, debt 6 AI factors moat, what no ratio measures 2,000+ data points verified, per stock, median

69 individual criteria per stock, every one traceable See the method →

Price vs Fair Value

$77.60 $11.66 Fair Value $21.45 Jun 2021 Sep 2026

White line = price, green steps = our fair value per fiscal year, dashed = 300-day average. As of Sep 23, 2026.

How to read this chart

60‑month range $11.66 – $77.60 · fair‑value band $14.25 – $35.52 · the $34.88 price screens above the $21.45 fair value. Green steps = our fair value per fiscal year (point-in-time, no hindsight). 2 fiscal years are left out: there the valuation rested on only a fraction of the usual models. Dashed = 300-day average. As of Sep 23, 2026.

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Company profile

Castle Biosciences, Inc., a molecular diagnostics company, provides test solutions for the diagnosis and treatment of dermatologic cancers, Barrett's esophagus (BE), atopic dermatitis (AD), and uveal melanoma.

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Castle Biosciences, Inc., a molecular diagnostics company, provides test solutions for the diagnosis and treatment of dermatologic cancers, Barrett's esophagus (BE), atopic dermatitis (AD), and uveal melanoma. The company offers DecisionDx-Melanoma, a risk stratification gene expression profile (GEP) test that predicts the likelihood of a positive sentinel lymph node and the risk of metastasis for patients with invasive cutaneous melanoma; TissueCypher, a risk stratification spatialomics test to predict future development of high-grade dysplasia and/or esophageal cancer in patients with non-dysplastic, indefinite dysplasia, and low-grade dysplasia BE; AdvanceAD-Tx, a non-invasive GEP test which is designed to guide systemic treatment selection for patients aged 12 years and older with moderateto-severe AD; DecisionDx-SCC, a GEP test for cutaneous squamous cell carcinoma; and MyPath Melanoma, a diagnostic GEP test for use in patients with difficult-to-diagnose melanocytic lesions. It also provides DecisionDx-UM, a risk stratification GEP test that predicts the risk of metastasis for patients with uveal melanoma. The company offers its products to dermatology and gastroenterology markets. The company was incorporated in 2007 and is headquartered in Friendswood, Texas.

Stock analysis

Castle Biosciences Inc (CSTL) currently trades at $34.88, while our model-based Fair Value estimate is $21.45, implying the stock looks roughly 62.6% overvalued today.

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Valuation

Bull case: the Growth DCF group reads highest at a median of $23.55 per share, and 0 of the 7 models we run sit above the $34.88 price.

Bear case: the Asset-Based group reads lowest at $10.40, and 7 of the 7 models stay below the price. Evidence for this calculation is low.

Scenario range: $14.25 (bear) to $35.52 (bull), the price of $34.88 sits inside it. Bear and bull are the same models on cautious and optimistic assumptions, a range, not a price target.

Quality & growth

The Quality Score stands at 46/100 (below-average quality), in the Healthcare sector.

Mixed Growth: Revenue is growing, but margins or cash flow do not fully confirm the trend.

Castle Biosciences Inc reported revenue of $344M in FY2025 versus $94.1M in FY2021, a compound +38.3%/yr. Reported net income was −$24.2M in FY2025.

Key figures

Market cap $1.0B · P/S ratio 1.88 · EPS (TTM) $−0.4200 · Net margin −7.0% · Return on equity −2.9% · Return on assets (EBIT) −9.1% · Operating margin −22.0% · Revenue (TTM) $340M.

Competitive moat

Our AI-assisted moat analysis scores the competitive advantage at 48 out of 100 (low confidence).

What moves the price

The share trades about 19% below its 52-week high and 92% above its 52-week low, currently above its 200-day average.

For context, the median of 10 Healthcare peers we cover trades at −5% fair-value upside, at −39%, CSTL screens richer than that median.

Fair Value models

Bear $14.25 Fair Value $21.45 Bull $35.52
Model ⓘEach model values the company its own way (discounted cash flow, earnings, assets, dividends). The fair value above is their evidence-weighted blend, not the output of a single model. Bear ⓘBear = the cautious scenario: the same model computed with conservative anchors (lower growth, margins and valuation multiples). Together with Bull it frames a plausible valuation range, not a price target.BaseBull ⓘBull = the optimistic scenario: the same model computed with favourable anchors (higher growth, margins and valuation multiples). Together with Bear it frames a plausible valuation range, not a price target. Evidence ⓘEvidence = how well-backed THIS model's estimate is for this stock (0–100): how complete and reliable its input data are, and how well the model fits the company. The final Fair Value is an evidence-weighted blend, so better-evidenced models count more. Green ≥70, amber 50–69, grey below 50.
Highest evidence
FCF DCF $16.27 $22.13 $39.64 76
Growth DCF $15.47 $24.16 $37.83 75
5Y Revenue Exit $13.91 $21.04 $35.92 68
All 7 models by family
DCF Models
FCF DCF $16.27 $22.13 $39.64 76
5Y Revenue Exit $13.91 $21.04 $35.92 68
10Y Revenue Exit $14.44 $26.17 $33.27 65
Multiples
EV/Revenue $12.03 $15.67 $19.31 54
Asset-Based
NCAV (Graham) $7.76 $10.40 $15.53 54
Growth DCF
Growth DCF $15.47 $24.16 $37.83 75
Rev-Margin DCF $14.96 $23.55 $41.56 68

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Quality Score breakdown

Overall quality 46/100

Of which business quality 51 · Market factors (momentum, volatility) 68

Profitability 26
Margins and returns on capital today
Quality Growth 18
Are margins and returns improving?
Cashflow 42
Earnings quality: real cash, not paper profit
Fin. Strength 92
Balance sheet, leverage, solvency risk
Investment 60
Disciplined investing over empire-building
Low Volatility 34
Calm price path (market factor)
Momentum 88
Price trend over the last 3–12 months (market factor)
52W Momentum 75
Distance to the 52-week high (market factor)
Net Issuance 68
Share count: buybacks or dilution?

Open the full quality analysis →

Revenue & earnings trend

Growth Quality ⓘGrowth is valuable only when reinvestment earns attractive returns (Aswath Damodaran): sustainable growth depends on return on capital, reinvestment and efficiency. Basis: total company revenue over the periods shown on the cards (3Y/5Y/all years), not per share, so a merger can show up as a growth jump; per-share earnings growth is in the value-creation card. 67/100
Revenue is growing, but margins or cash flow do not fully confirm the trend.
Revenue growth 1 year
+3.7%
Revenue growth 3 years ⓘMeasures the company's TOTAL revenue from reported annual statements: compound average growth per year (CAGR) from the fiscal year 3, 5 or N years back to the most recent comparable fiscal year. Not per share: buybacks do not change this number, and a merger can appear as a growth jump. Per-share growth (which does include buybacks) is in the value-creation card.
+35.9%
Revenue growth 5 years ⓘMeasures the company's TOTAL revenue from reported annual statements: compound average growth per year (CAGR) from the fiscal year 3, 5 or N years back to the most recent comparable fiscal year. Not per share: buybacks do not change this number, and a merger can appear as a growth jump. Per-share growth (which does include buybacks) is in the value-creation card.
+40.6%
Start year 2020 (pandemic)
Revenue growth 8 years ⓘMeasures the company's TOTAL revenue from reported annual statements: compound average growth per year (CAGR) from the fiscal year 3, 5 or N years back to the most recent comparable fiscal year. Not per share: buybacks do not change this number, and a merger can appear as a growth jump. Per-share growth (which does include buybacks) is in the value-creation card.
+49.6%
Profit margin (trend) ⓘOperating margin then vs now, from reported annual statements. A falling margin after a boom year is the classic peak-earnings signal: the growth rate then leans on an inflated base.
−10.4% (2020) → −12.4% (2025)
What shareholders gained per year ⓘWe only publish this rate when it is defensible. Reason: fiscal 2025 is a loss year, no rate is defined from a loss
not computed

Growth Forecast

A lot of optimism in the price
The price assumes less growth than the company has delivered so far and more than analysts expect.
What the price assumes ⓘThis turns our valuation around: instead of asking what the share is worth, it asks what growth the current price requires. It uses the cash the company keeps after all spending (free cash flow), the same discount rate as our models, five years of growth, then slowing evenly to 2 % a year by year ten. Compared with the analysts' sales forecasts extended to the same five years (at least three analysts, for context only, it does not enter the Fair Value): within 3 percentage points counts as "in line" (amber), below that little optimism (green), above that a lot of optimism (red).
+18.1%
Yearly growth needed for the next five years to justify today's price.
What forecasts expect ⓘAnalysts publish sales forecasts for the next two fiscal years. For the years after that, growth slows evenly to 2 % a year by year ten (2 % is the long-run rate our models use). Projected years are marked as such.
+8.2%
Yearly sales growth analysts expect, extended to five years.
After inflation (USA: IMF forecast 2.4% a year to 2030, 3.1% from 2016 to 2025) that is about +15.3% a year for the price and +5.7% for the forecasts.
Forecast 2026 (sales)+2.4%
Forecast 2027 (sales)+11.5%
Projected 2028 (sales)+10.3%
Projected 2029 (sales)+9.1%
Projected 2030 (sales)+7.9%

CSTL screens 63% overvalued. Compare with Thermo Fisher Scientific Inc →

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Peer GroupⓘHow this stock ranks against its industry: the green marker is this stock, the band is the typical 25–75% peer range, and the tick is the median.Diagnostics & Research · 141 stocks

Beats the industry median on 1/10 measures
Overall it trails its industry peers.
Valuation
Quality Score 46 · Below median
Fair Value upside −39% · Below median
Profitability
Return on assets −4% · Below median
Net margin (TTM) −4% · Below median
Operating margin (TTM) −22% · Bottom 25%
Growth and dividend
Revenue growth −5% · Below median
Balance sheet
Debt / equity 0.02× · Below median

Valuation Multiplesvs Diagnostics & Research median · lower = cheaper

P/B 2.15× · Pricier than median
P/S (TTM) 2.97× · Pricier than median
P/FCF 35.7× · Priciest 25%

Strength profile in five axes (Snowflake)

VALUEFUTUREPASTHEALTHDIVIDEND
This stock
VALUEFUTUREPASTHEALTHDIVIDEND
Sector peers
VALUE (fair-value potential)0 · sector 0
FUTURE (revenue growth)0 · sector 25
PAST (return on equity)0 · sector 9
HEALTH (low debt)99 · sector 95
DIVIDEND (yield)0 · sector 30

VALUE 0: the price sits above our fair-value range.

Context: sector, industry, market

Values & ESG

Does this company touch areas you may want to avoid? The classification is inferred from sector and industry.

None of the checked exposures detected

Similar stocks

10 more Diagnostics & Research stocks, each showing price versus our Fair Value estimate.

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Thermo Fisher Scientific Inc TMO $658.52 $682.58 +4%
Danaher Corporation DHR $221.09 $207.76 −6%
WuXi AppTec Co 2359 HK$207.60 HK$228.36 +10%
Lonza Group LONN CHF 562.80 CHF 151.69 −73%
IDEXX Laboratories, Inc IDXX $521.50 $495.84 −5%
Agilent Technologies, Inc A $167.26 $63.90 −62%
Waters Corporation WAT $425.74 $106.31 −75%
IQVIA Holdings IQV $270.09 $295.80 +10%
Illumina, Inc ILMN $247.46 $272.21 +10%
Mettler-Toledo International Inc MTD $1,491 $635.75 −57%

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Castle Biosciences Inc · Fair Value
$21.45 −63%Fair Value
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Cite: Fair Value Calculator (2026). "Castle Biosciences Inc Fair Value". https://www.fairvalue-calculator.com/stock/CSTL

Frequently asked questions

Is Castle Biosciences Inc (CSTL) overvalued or undervalued?
As of Sep 23, 2026, our model estimates a fair value of $21.45 versus a price of $34.88, about −39% upside (overvalued).
What is the fair value of CSTL?
Our model-based fair value for Castle Biosciences Inc is $21.45 (as of Sep 23, 2026), built from audited fundamentals. The current price: $34.88.
What is the quality score of CSTL?
Castle Biosciences Inc has a Quality Score of 46/100. It measures business quality (profitability, growth, cash flow, balance-sheet strength, investment discipline, share issuance). Market factors such as price momentum and volatility do not enter the number; they are shown separately in the detail view.
What is the price target for Castle Biosciences Inc (CSTL)?
Our model-based price target is the fair value of $21.45 (as of Sep 23, 2026) from 7 valuation models. Cautious scenario $14.25, optimistic scenario $35.52. It is a calculation from audited fundamentals, not an analyst target.
What is the Castle Biosciences Inc stock forecast for 2026?
Our models put fair value at $21.45, about −39% upside versus a price of $34.88 (overvalued). Cautious scenario $14.25, optimistic scenario $35.52. The calculation is refreshed regularly with new filings.
What is the revenue of Castle Biosciences Inc (CSTL)?
Castle Biosciences Inc reported trailing-twelve-month revenue of about $340M (latest available figure, as of Sep 23, 2026).
What growth is priced into Castle Biosciences Inc (CSTL)?
For today's price to be fair in a discounted-cash-flow model, Castle Biosciences Inc would have to grow free cash flow by +18.1 % per year for five years (discount rate 11.3 %, then slowing evenly to 2 % perpetual growth by year ten). Over the last 5 years revenue grew +40.6 % per year. As of Sep 23, 2026.
What discount rate (WACC) does the fair value of CSTL use?
Our models discount Castle Biosciences Inc at 11.3 %: a base by market capitalisation (small), damped by beta 1.02, country premium for USA. The same rate applies in all 26 models.
What is a reverse DCF?
A reverse DCF turns the usual calculation around. Instead of deriving a value from assumptions, it takes today's price as given and asks: what free-cash-flow growth would a company have to deliver for exactly this price to be fair? The result is not a forecast but the expectation already priced in. For Castle Biosciences Inc that is +18.1 % per year a year over ten years, using the same discount rate (11.3 %) and the same formula as our fair value.
How much growth has Castle Biosciences Inc (CSTL) delivered so far?
Over the past 5 years revenue at Castle Biosciences Inc grew +40.6 % a year. The price currently implies +18.1 % per year free-cash-flow growth a year. Comparing the two shows how much confidence is in the price: if it demands more than has been delivered, the business has to accelerate for the maths to work.
How fast is the sector of Castle Biosciences Inc (CSTL) growing?
The median revenue growth in the sector is +4.2 % a year. That is the yardstick for the growth priced into Castle Biosciences Inc (+18.1 % per year a year): it shows whether the expectation is within the usual range or beyond it.
What is the free cash flow yield of Castle Biosciences Inc (CSTL)?
The free-cash-flow yield on the price is 2.80 %: that much free cash flow Castle Biosciences Inc produces per unit of market value. When it exceeds the discount rate of our models (11.3 %), the business already earns more than its cost of capital demands, and the price needs little additional growth.
What is the intrinsic value of Castle Biosciences Inc (CSTL)?
Intrinsic value and fair value mean the same thing: what the business is worth on its numbers, independent of the share price. For Castle Biosciences Inc it is $21.45 per share (as of Sep 23, 2026), against a price of $34.88. It is the blended result of 7 valuation models (cash flow, earnings, asset, dividend).
Is Castle Biosciences Inc stock overvalued or undervalued in 2026?
As of Sep 23, 2026, CSTL trades above its calculated fair value: price $34.88, fair value $21.45, a gap of about −39% (overvalued). The calculation is refreshed with each new quarterly report, so the verdict can change during the year.
Is fair value the same as the market price of CSTL?
No. The price is what the market pays today ($34.88); the fair value is what the company's own numbers justify ($21.45). For Castle Biosciences Inc the two are $13.43 per share apart. That gap is exactly why we show both numbers side by side.
How much is Castle Biosciences Inc worth?
The market values Castle Biosciences Inc at about $1.0B (market capitalisation, as of Sep 23, 2026). Per share that is $34.88; our models calculate a fair value of $21.45 per share.
What do the bullish and bearish scenarios say about CSTL?
Our models span a range for Castle Biosciences Inc: cautious scenario $14.25, base $21.45, optimistic $35.52 per share (as of Sep 23, 2026, price $34.88). The range comes from different growth and margin assumptions, not from analyst opinions.
How solid is the balance sheet of Castle Biosciences Inc (CSTL)?
Balance-sheet figures for Castle Biosciences Inc (as of Sep 23, 2026): return on equity −2.9%, debt of 0.02 per unit of equity. They feed the Quality Score of 46/100, which measures business quality independently of the share price.
How far is CSTL from its 52-week high?
Castle Biosciences Inc trades at $34.88, about 19% below its 52-week high of $43.04 and 92% above the low of $18.15 (as of Sep 23, 2026). Distance from the high says nothing about value: that is what the fair value of $21.45 is for.
Which stocks are comparable to Castle Biosciences Inc?
From the same area (Healthcare) we also value Thermo Fisher Scientific Inc, Danaher Corporation, WuXi AppTec Co, Lonza Group, among others. Each of them has its own fair-value calculation on this site using the same models, so the comparison is like for like.
Is Castle Biosciences Inc stock attractive at the current price?
The data as of Sep 23, 2026: price $34.88, calculated fair value $21.45 (−39%), Quality Score 46/100, from 7 models. Whether that fits your horizon and risk tolerance is your call. We provide the calculation, not investment advice.
How is the fair value of CSTL calculated?
We run Castle Biosciences Inc through 7 models from four families: discounted cash flow, earnings models, asset and balance-sheet models, and dividend models. Every model gets the same audited fundamentals; the result is the weighted average of $21.45, with the spread shown as a cautious and an optimistic scenario.
Is it still worth investing in stocks now?
The global stock market currently sits 14.1 % above its aggregate fair value. Castle Biosciences Inc itself currently trades above fair value. An expensive market is no reason to stay out and no reason to buy everything at once: keep a broad savings plan running, buy single stocks only with money you can do without, and hold part of your money liquid while the market is high. The full picture including sectors is on is it worth investing now.
What is the share price of Castle Biosciences Inc (CSTL)?
The closing price on Sep 23, 2026 was $34.88. Our model-based fair value is $21.45, about −39% upside (overvalued). We carry closing prices from our data provider, not a live tick.
What should I pay attention to with Castle Biosciences Inc right now?
The large gap to fair value rests on thin data (low evidence): fewer applicable models and a shorter history. Read it with extra caution. Solid but not exceptional quality (46/100) and above fair value, neither a clear bargain nor a standout compounder. A fairly wide model range ($14.25 to $35.52) leaves room in how you read the outcome.

Key figures of Castle Biosciences Inc

How large is the market capitalisation of Castle Biosciences Inc (CSTL)?
The market capitalisation of Castle Biosciences Inc is $1.0B. The stock-market value of the whole company: share price times number of shares. It is what the market asks for the entire business today.
What is the P/S ratio of Castle Biosciences Inc (CSTL)?
The price-to-sales ratio of Castle Biosciences Inc is 1.88 (last twelve months). Price to sales: market value relative to yearly revenue. Useful when profit is thin or distorted.
What are the earnings per share of Castle Biosciences Inc (CSTL)?
Earnings per share at Castle Biosciences Inc are $−0.4200. Earnings per share over the last twelve months: total profit spread across every single share.
What is the net margin of Castle Biosciences Inc (CSTL)?
The net margin of Castle Biosciences Inc is −7.0% (fiscal year 2025). How much of every unit of revenue ends up as profit. 10% means 10 cents of profit per dollar of sales.
What is the return on equity of Castle Biosciences Inc (CSTL)?
The return on equity (ROE) of Castle Biosciences Inc is −2.9% (last twelve months). Profit relative to shareholders' equity, how efficiently the company works with its owners' money.
What is the EBIT return on assets of Castle Biosciences Inc (CSTL)?
On an EBIT basis the return on assets of Castle Biosciences Inc is −9.1% (avg 5y). Operating profit (EBIT) relative to everything the company owns, as a multi-year average. It describes the business model rather than one good or bad year.
What is the operating margin of Castle Biosciences Inc (CSTL)?
The operating margin of Castle Biosciences Inc is −22.0% (last twelve months). Profit from the core business (before interest and taxes) relative to revenue.
How fast is revenue growing at Castle Biosciences Inc (CSTL)?
Revenue at Castle Biosciences Inc is growing −4.9% versus a year earlier (3y avg +35.9%). How much revenue grew versus a year earlier (YoY). The 3-year average next to it puts the single year in context.
How fast are earnings growing at Castle Biosciences Inc (CSTL)?
Earnings per share at Castle Biosciences Inc are growing −51.6% versus a year earlier. How much earnings per share grew versus a year earlier.
How much net cash does Castle Biosciences Inc (CSTL) hold?
Castle Biosciences Inc holds more cash than debt, $79.8M net (fiscal year 2025). The company holds more cash than debt, a safety cushion.
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