Market Sizing

Rigorous market sizing using dual TAM/SAM/SOM methodology (top-down and bottom-up) with reconciliation, sensitivity analysis, and growth projection.

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Required Inputs

Input	Description	Required?
Industry / product category	What market is being sized	Yes
Geographic scope	Country, region, or global	Yes
Target customer segment(s)	Who buys this product/service	Yes
Product/service definition	What is being sold, at what price point	Yes
Time horizon	Current year and projection period (e.g., 2026-2031)	Yes
Company capabilities	Current reach, channels, capacity constraints	For SOM
Known data points	Any existing research, revenue figures, customer counts	If available
Currency	Reporting currency	Yes

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Execution Steps

Step 1: Define Market Boundaries

Establish precise definitions before any calculation:

1. Product scope: What products/services are included and excluded?
2. Customer scope: Which buyer segments (B2B, B2C, enterprise, SMB)?
3. Geographic scope: Which countries/regions? Regulatory differences?
4. Value chain scope: Which parts of the value chain (manufacturing, distribution, SaaS layer)?

Document boundary decisions explicitly — these are the #1 source of market sizing disagreements.

Step 2: Top-Down Analysis

Start from the largest defensible number and narrow:

1. Identify macro data sources (in order of reliability):

   • Government statistics (Census, BLS, Eurostat, national statistical offices)
   • Industry association reports (trade bodies, industry groups)
   • Analyst reports (Gartner, IDC, Forrester, Statista, IBISWorld)
   • Public company filings (10-K revenue disclosures, earnings calls)
   • Academic research and published studies

2. Calculate top-down TAM:

   • Total industry revenue globally or in target geography
   • OR: Total number of potential buyers x average annual spend per buyer

3. Apply segmentation filters for SAM:

   • Filter by geography served
   • Filter by customer segment targeted
   • Filter by product/service fit (what portion of spend your offering addresses)
   • Filter by channel accessibility

4. Apply penetration and capacity constraints for SOM:

   • Realistic market share given competitive landscape (use analogues)
   • Channel and sales capacity limits
   • Brand awareness and reach constraints
   • Time-to-penetrate considerations

Step 3: Bottom-Up Analysis

Build from unit economics upward:

1. Count target customers:

   • Identify the number of potential buyers in each segment
   • Use company registries, industry databases, demographic data

2. Estimate purchase behavior:

   • Average deal size / ticket price
   • Purchase frequency (annual, monthly, one-time)
   • Adoption rate by segment (early adopters vs. mainstream)

3. Calculate bottom-up TAM:

   TAM = Σ (Customers_in_segment × Price × Purchase_frequency) for all segments
   

4. Calculate bottom-up SAM:

   SAM = Σ (Reachable_customers × Price × Frequency) for served segments
   

5. Calculate bottom-up SOM:

   SOM = SAM × Expected_penetration_rate × Conversion_rate
   

Step 4: Reconciliation

Compare top-down and bottom-up estimates:

1. Calculate variance: If top-down and bottom-up differ by >30%, investigate why
2. Identify discrepancy sources:
   • Pricing assumptions differ?
   • Customer count estimates differ?
   • Scope definitions misaligned?
3. Triangulate: Use a third method (e.g., analogue-based, value-theory) if gap persists
4. Select final estimate: State which approach is primary and why; use the other as a sanity check
5. Document confidence level: High (estimates within 15%), Medium (15-40% range), Low (>40% range)

Step 5: Growth Rate Projection

Project market growth over the time horizon:

1. Historical growth rate: CAGR over last 3-5 years from industry data
2. Driver-based growth model:
   • Population/business formation growth
   • Penetration rate increase (adoption curve position)
   • Price changes (inflation, premiumization, commoditization)
   • Usage intensity changes
   • Regulatory tailwinds/headwinds
3. Analogue comparison: How did similar markets grow? (e.g., cloud adoption curve for AI SaaS)
4. Adoption curve positioning: Where on the S-curve is this market? (innovators → early majority → late majority)

Growth Phase	Typical Annual Growth	Characteristics
Emerging	30-80%+	Pre-product/market fit, few players
High growth	15-30%	Product/market fit proven, competition entering
Growth	8-15%	Market maturing, consolidation beginning
Mature	2-8%	Established players, GDP+ growth
Declining	<0%	Substitution, obsolescence

Step 6: Sensitivity Analysis

Test key assumptions:

1. Identify the 3-5 variables with the highest impact on market size (typically: customer count, price, adoption rate, growth rate)
2. Define ranges for each variable (pessimistic, base, optimistic)
3. Build sensitivity table: Show how TAM/SAM/SOM change as each variable moves
4. Tornado chart inputs: Rank variables by impact magnitude

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Output Template

Market Sizing: [Industry/Product] — [Geography]

Date: [Date] | Prepared for: [Client/Project] | Confidence Level: [High/Medium/Low]

1. Market Definition & Boundaries

Dimension	Included	Excluded
Products/Services	[Specific offerings]	[Adjacent categories excluded]
Customer Segments	[Target segments]	[Non-target segments]
Geographies	[Countries/regions]	[Out-of-scope regions]
Value Chain	[Stages included]	[Stages excluded]

2. TAM / SAM / SOM Waterfall

Metric	Top-Down Estimate	Bottom-Up Estimate	Reconciled Estimate	Confidence
TAM (Total Addressable Market)	$[X]B	$[X]B	$[X]B	[H/M/L]
SAM (Serviceable Addressable Market)	$[X]B	$[X]B	$[X]B	[H/M/L]
SOM (Serviceable Obtainable Market)	$[X]M	$[X]M	$[X]M	[H/M/L]

SAM as % of TAM: [X]% — [Explanation of narrowing factors] SOM as % of SAM: [X]% — [Explanation of capture assumptions]

3. Top-Down Methodology

Step	Value	Source	Notes
Global industry revenue	$[X]B	[Source, Year]	[Methodology note]
Geographic filter ([Region])	$[X]B	[Source]	[X]% of global
Segment filter ([Segment])	$[X]B	[Source]	[X]% of regional
Product relevance filter	$[X]B	[Assumption]	[X]% of segment spend
Top-Down TAM	$[X]B

4. Bottom-Up Methodology

Segment	# of Customers	Avg. Annual Spend	Segment TAM
[Segment 1]	[N]	$[X]	$[X]M
[Segment 2]	[N]	$[X]	$[X]M
[Segment 3]	[N]	$[X]	$[X]M
Total Bottom-Up TAM	[N]	$[X] avg	$[X]B

5. Reconciliation

Approach	TAM	SAM	SOM	Variance vs. Reconciled
Top-Down	$[X]B	$[X]B	$[X]M	[+/-X]%
Bottom-Up	$[X]B	$[X]B	$[X]M	[+/-X]%
Reconciled	$[X]B	$[X]B	$[X]M	—

Reconciliation notes: [Explain why one approach is favored, what drove differences, how you resolved them]

6. Market Growth Projection

Year	TAM	Growth %	SAM	SOM
[Current]	$[X]B	—	$[X]B	$[X]M
[+1]	$[X]B	[X]%	$[X]B	$[X]M
[+2]	$[X]B	[X]%	$[X]B	$[X]M
[+3]	$[X]B	[X]%	$[X]B	$[X]M
[+5]	$[X]B	[X]%	$[X]B	$[X]M

Growth CAGR ([Current]-[+5]): TAM [X]% | SAM [X]% | SOM [X]%

Key growth drivers:

1. [Driver 1 — quantified impact]
2. [Driver 2 — quantified impact]
3. [Driver 3 — quantified impact]

7. Sensitivity Analysis

Tornado Chart — Impact on TAM (Base: $[X]B)

Variable	Low Case	Base Case	High Case	TAM Range
[Variable 1]	[Low]	[Base]	[High]	$[X]B - $[X]B
[Variable 2]	[Low]	[Base]	[High]	$[X]B - $[X]B
[Variable 3]	[Low]	[Base]	[High]	$[X]B - $[X]B
[Variable 4]	[Low]	[Base]	[High]	$[X]B - $[X]B

Combined scenario range: $[Low]B (pessimistic) → $[Base]B (base) → $[High]B (optimistic)

8. Data Sources & Confidence Assessment

Data Point	Source	Year	Confidence	Risk
[Data point 1]	[Source]	[Year]	[H/M/L]	[Key risk to accuracy]
[Data point 2]	[Source]	[Year]	[H/M/L]	[Key risk to accuracy]

9. Key Assumptions & Caveats

1. [Assumption 1 — impact if wrong]
2. [Assumption 2 — impact if wrong]
3. [Assumption 3 — impact if wrong]

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Quality Checks

• TAM, SAM, and SOM are each calculated using BOTH top-down and bottom-up approaches
• Top-down and bottom-up estimates are reconciled with variance explained
• Every data point cites a specific source with year
• Market boundaries (product, geography, customer, value chain) are explicitly defined
• SAM narrowing from TAM is explained with specific filters and percentages
• SOM includes realistic penetration assumptions, not aspirational targets
• Growth projections use driver-based methodology, not just trend extrapolation
• Sensitivity analysis tests at least 3 key variables with defined ranges
• Confidence level (High/Medium/Low) is stated for each major estimate
• Currency, time period, and geographic scope are stated in every table header
• No circular reasoning (not using own revenue targets to justify market size)
• Sanity checks applied: per-capita spend, comparison to adjacent markets, public company revenue benchmarks