Market Sizing (TAM/SAM/SOM)
Overview
Market sizing quantifies the revenue opportunity in a market. The TAM/SAM/SOM framework provides progressively refined estimates from total market to realistically achievable share.
Key Definitions
TAM (Total Addressable Market)
- •Total global market demand for a product/service
- •Assumes 100% market share (theoretical maximum)
- •Useful for understanding ceiling and investor conversations
SAM (Serviceable Addressable Market)
- •Portion of TAM targetable with current business model
- •Considers geographic, demographic, or segment constraints
- •More realistic than TAM
SOM (Serviceable Obtainable Market)
- •Realistic market share achievable in near term (1-3 years)
- •Considers competition, resources, and go-to-market capability
- •Most relevant for planning
Calculation Methodologies
Top-Down Approach
Start with large market data, narrow down:
- •Find industry market size from analyst reports
- •Apply relevant percentage for target segment
- •Adjust for geography if not global
- •Factor growth rates for projections
Example:
- •Global SaaS market: $200B (TAM)
- •HR SaaS segment: 15% → $30B (TAM refined)
- •North America: 40% → $12B (SAM)
- •Achievable share 2%: $240M (SOM)
Pros: Fast, uses existing research Cons: May miss nuances, depends on source quality
Bottom-Up Approach
Build from unit economics upward:
- •Identify target customer count
- •Estimate price per customer
- •Calculate total revenue potential
Example:
- •Target customers: 50,000 SMBs
- •Average contract value: $5,000/year
- •Total: $250M (SOM)
- •Expand to all SMBs (500,000): $2.5B (SAM)
- •Include enterprise: $10B (TAM)
Pros: More defensible, validates assumptions Cons: Slower, requires customer data
Value Theory Approach
Estimate based on value delivered:
- •Calculate customer pain point cost
- •Estimate value of solution
- •Apply capture rate (typically 10-30% of value)
Example:
- •Customer loses $100K/year to problem
- •Solution captures 20%: $20K willingness to pay
- •100,000 potential customers: $2B market
Trend Indicators
Apply three-valued logic to growth projections:
- •INC (Increasing): Market growing >10% annually
- •CONST (Constant): Market growth 0-10% annually
- •DEC (Decreasing): Market contracting
Document evidence for each indicator:
- •INC: "Analyst projects 25% CAGR through 2027"
- •CONST: "Mature market with 3% annual growth"
- •DEC: "Legacy technology being displaced"
Data Sources
Primary Sources (Most Reliable):
- •Industry analyst reports (Gartner, Forrester, IDC)
- •Government statistics (Census, BLS)
- •Trade association data
- •Company financials (public companies)
Secondary Sources:
- •Market research firms (Statista, IBISWorld)
- •News articles citing research
- •Industry publications
- •Competitor disclosures
Estimation Sources (Use Carefully):
- •LinkedIn job counts × average salary
- •Google Trends relative volume
- •App store downloads × price
- •Website traffic estimates
Output Structure
## Market Sizing Summary | Metric | Value | Growth | Trend | |--------|-------|--------|-------| | TAM | $X.XB | X% CAGR | INC/DEC/CONST | | SAM | $X.XB | X% CAGR | INC/DEC/CONST | | SOM | $XXM | - | - | ## Methodology [Top-down / Bottom-up / Hybrid] ## TAM Calculation [Step-by-step with sources] ## SAM Derivation [How SAM was narrowed from TAM] ## SOM Justification [Realistic share rationale] ## Key Assumptions 1. [Assumption and sensitivity] 2. [Assumption and sensitivity] ## Data Sources - [Source 1]: [What it provided] - [Source 2]: [What it provided] ## Confidence Level [High/Medium/Low with explanation]
Common Pitfalls
- •Double-counting: Ensure segments don't overlap
- •Currency confusion: Specify USD/EUR and year
- •Stale data: Note data age, adjust for growth
- •Over-optimism: SOM should be conservative
- •Missing context: Include methodology for credibility
Scenario Modeling
For uncertain markets, provide range:
| Scenario | TAM | SAM | SOM |
|---|---|---|---|
| Bear | $5B | $500M | $10M |
| Base | $8B | $800M | $25M |
| Bull | $12B | $1.2B | $50M |
Use transitional scenario graphs to show how market might evolve between scenarios.
Additional Resources
For detailed templates and examples, see:
- •
references/sizing-methodologies.md- Complete methodology guide - •
references/data-sources.md- Source reliability ratings - •
examples/market-sizing-report.md- Sample sizing report