| name | market-sizing-frameworks |
| description | Master TAM/SAM/SOM calculations, market sizing methodologies, and validation frameworks. Use when assessing market opportunity, validating business viability, planning market entry, estimating revenue potential, or determining if a market is worth pursuing. Covers bottom-up, top-down, and value theory sizing methods, competitive analysis, and systematic validation approaches. |
Market Sizing Frameworks
Frameworks and methodologies for estimating market size and validating market opportunity.
Overview
Market sizing answers the critical question: "Is this opportunity large enough to pursue?" It provides the foundation for strategic decisions, resource allocation, and investment prioritization.
Core Principle: Market sizing is educated guessing with documented assumptions. The goal is reasonable estimates and order-of-magnitude accuracy (is it $1M, $10M, or $100M?), not false precision.
Key Insight: Always use multiple methods (bottom-up, top-down, value theory) to triangulate and validate estimates. If methods disagree by more than 2-3x, your assumptions need scrutiny.
When to Use This Skill
Auto-loaded by agents:
market-analyst - For TAM/SAM/SOM calculation and market validation
Use when you need to:
- Assess if a market opportunity is worth pursuing
- Calculate TAM, SAM, and SOM for business planning
- Validate market assumptions before building
- Support fundraising or strategic planning
- Evaluate competitive landscape impact on opportunity
- Determine realistic revenue projections
The Three-Tier Framework
TAM (Total Addressable Market)
Definition: Total revenue opportunity if you achieved 100% market share globally.
Purpose: Understand the absolute ceiling of opportunity.
Typical Range:
- Side project: $1M+ TAM minimum
- Full-time business: $10M+ TAM minimum
- VC-backed startup: $100M+ TAM minimum
Calculation: See three methods below.
SAM (Serviceable Addressable Market)
Definition: Portion of TAM you can realistically serve given your business model, geography, and product capabilities.
Purpose: Your realistic target market after applying real-world constraints.
Filters to Apply:
- Geographic reach: Where can you operate?
- Customer segment: Which types of customers fit your solution?
- Product capabilities: Who can your product actually serve?
- Distribution channels: Who can you reach?
Typical Range: SAM is usually 10-40% of TAM for focused products.
Formula:
SAM = TAM × Geographic % × Segment % × Product Fit % × Distribution %
SOM (Serviceable Obtainable Market)
Definition: Portion of SAM you can realistically capture in the near term (1-3 years).
Purpose: Your achievable revenue target given resources, competition, and time constraints.
Realistic Benchmarks:
- Year 1: 0.1-0.5% of SAM (new products)
- Year 3: 1-5% of SAM (if successful)
- Year 5: 5-15% of SAM (market leader position)
Formula:
SOM = SAM × Realistic Market Share %
Reality Check: Convert SOM to customer count. Is that number achievable per month/week?
Three Market Sizing Methods
Always use all three methods for robust validation. If they disagree significantly, investigate your assumptions.
Method 1: Bottom-Up (Most Reliable)
Approach: Count actual customers and multiply by revenue per customer.
Formula:
TAM = Total Potential Customers × Average Revenue per Customer
Process:
- Define who is a potential customer (be specific!)
- Count them using reliable data sources
- Apply realistic adoption/penetration filters
- Estimate average annual revenue per customer
- Multiply to get TAM
Strengths:
- Most grounded in reality
- Easy to validate assumptions
- Can name actual customers
When to Use: Always start here as your primary method.
Complete methodology: See references/market-sizing-methodologies.md for detailed step-by-step process with examples.
Method 2: Top-Down (For Validation)
Approach: Start with total market size and estimate your segment percentage.
Formula:
TAM = Total Market Size × Your Segment %
Process:
- Find comparable market size data (Gartner, IDC, etc.)
- Identify what percentage is your specific segment
- Apply multiple filters to narrow down
- Compare to bottom-up calculation
Strengths:
- Quick sanity check
- Uses industry research
- Good for validation
Weaknesses:
- Often produces inflated numbers
- Hard to validate percentages
- Can feel like guesswork
When to Use: As secondary validation, never as primary method.
Complete methodology: See references/market-sizing-methodologies.md for examples and industry applications.
Method 3: Value Theory
Approach: Calculate value created for customers, then estimate capture rate.
Formula:
TAM = (Value Created per Customer × Potential Customers) × Capture Rate %
Process:
- Quantify value delivered (time saved, cost reduced, revenue increased)
- Calculate dollar value of that benefit
- Determine what percentage you can capture in pricing (typically 10-30%)
- Multiply by potential customer base
Strengths:
- Tests pricing assumptions
- Grounds estimates in customer value
- Helps justify pricing strategy
When to Use: To validate pricing is reasonable relative to value created.
Complete methodology: See references/market-sizing-methodologies.md for value calculation frameworks.
Validation Framework
The Reality Check Questions
Before trusting your market sizing, validate with these critical tests:
1. Can you name 10 specific potential customers?
- If no: Market may be too narrow or unclear
- If yes: Proceed with confidence
2. Are there existing competitors making money?
- If yes: Market is validated (good!)
- If no: Either no market exists OR huge greenfield (risky)
3. Does TAM > SAM > SOM make sense?
- Progression should be logical
- SAM typically 10-40% of TAM
- SOM Year 1 typically 0.1-1% of SAM
4. Is Year 1 SOM achievable with your resources?
- Convert to customer count per month
- Is that acquisition rate realistic?
- Do you have budget/capacity?
5. Is the market big enough to justify effort?
- Minimum thresholds matter
- Compare to your goals (bootstrap vs VC)
Complete validation checklist: See assets/market-validation-checklist.md for comprehensive 100+ point validation framework.
Common Mistakes to Avoid
- Confusing TAM with SAM - Be explicit which number you're discussing
- Top-down only sizing - Always validate with bottom-up
- Ignoring competition - Available market is smaller than total market
- Assuming linear growth - Use S-curves, not straight lines
- No customer names - If you can't name 10 customers, market may not exist
- One-and-done sizing - Update assumptions quarterly as you learn
Detailed guide: See references/market-sizing-best-practices.md for:
- How to avoid each mistake
- Industry-specific considerations
- Competitive landscape analysis
- Assumption management frameworks
- Sensitivity analysis approaches
- Case studies (Superhuman, Quibi, Figma, Slack)
Recommended Workflow
Step 1: Bottom-Up Calculation (Primary)
Use this as your primary estimate:
- Define universe of potential customers (be specific)
- Count them using reliable data sources
- Estimate realistic adoption/penetration percentage
- Determine average annual revenue per customer
- Calculate: TAM = Customers × Adoption % × Price
Tool: Use assets/market-sizing-calculator.md for step-by-step worksheet with formulas.
Step 2: Top-Down Validation (Secondary)
Validate your bottom-up with industry data:
- Find comparable market size from research firms
- Estimate what percentage is your segment
- Compare to bottom-up calculation
- If within 2-3x: Good confidence
- If >5x difference: Investigate assumptions
Step 3: Value Theory Check
Test pricing reasonableness:
- Quantify value delivered to customers
- Calculate dollar value of benefits
- Determine capture rate (10-30% typical)
- Validate pricing is within reasonable range
Step 4: Apply SAM Filters
Narrow TAM to realistic serviceable market:
Starting TAM: $__________
Geographic filter: × ____% = $__________
Segment filter: × ____% = $__________
Product fit filter: × ____% = $__________
Distribution filter: × ____% = $__________
Final SAM: $__________
Template: Use assets/tam-sam-som-template.md for complete calculation template.
Step 5: Calculate Realistic SOM
Project achievable market capture:
Conservative Approach:
- Year 1: 0.1-0.3% of SAM
- Year 2: 0.5-1% of SAM
- Year 3: 1-3% of SAM
Consider:
- Competitive intensity (high = lower %)
- Switching costs (high = lower %)
- Your differentiation (strong = higher %)
- Distribution advantage (strong = higher %)
Step 6: Validate Thoroughly
Run through comprehensive validation:
- Complete all reality checks
- Verify unit economics work (LTV:CAC ratio)
- Check competitive landscape math
- Model three scenarios (pessimistic, base, optimistic)
- Conduct sensitivity analysis on key assumptions
Validation tool: Use assets/market-validation-checklist.md for systematic validation.
Step 7: Document Assumptions
Critical for updating as you learn:
## Key Assumptions
1. Customer count: [number]
- Source: [where this came from]
- Confidence: [High/Medium/Low]
- Impact if wrong: [+/- X% on TAM]
2. Pricing: $[amount]/year
- Basis: [competitive analysis, value-based, etc.]
- Confidence: [High/Medium/Low]
- Impact if wrong: [direct 1:1 impact]
3. Adoption rate: [%]
- Basis: [customer interviews, analogies, etc.]
- Confidence: [High/Medium/Low]
- Impact if wrong: [+/- X% on TAM]
Templates and Tools
Calculation Tools
Complete TAM/SAM/SOM Template:
assets/tam-sam-som-template.md- Full calculation framework with all filters
- Includes validation checklist
- Assumption documentation section
- Sensitivity analysis worksheet
Step-by-Step Calculator:
assets/market-sizing-calculator.md- All three methods with formulas
- Worked examples
- Comparison framework
- Confidence scoring
Validation Checklist:
assets/market-validation-checklist.md- 100+ validation points
- Reality checks and red flags
- Customer count validation
- Pricing validation
- Competitive validation
Reference Guides
Comprehensive Methodologies
Complete Methods Guide:
references/market-sizing-methodologies.md- Detailed bottom-up, top-down, and value theory processes
- Industry-specific approaches (B2B SaaS, Consumer, Enterprise, Marketplace, Dev Tools)
- Method comparison and triangulation
- Data source recommendations
Best Practices Guide:
references/market-sizing-best-practices.md- Common mistakes and how to avoid them
- Validation frameworks
- Competitive landscape analysis
- Assumption management
- Sensitivity analysis
- Case studies: Superhuman, Quibi, Figma, Slack
- Advanced considerations (timing, geographic expansion, platform effects)
Summary
Market sizing is educated guessing - the goal is reasonable estimates with documented assumptions, not precision.
The Three-Step Approach:
- Calculate: Use all three methods (bottom-up, top-down, value theory)
- Validate: Reality-check with customers, competition, and economics
- Document: Track assumptions and update quarterly
Key Principles:
- Always start with bottom-up (most reliable)
- Use top-down only for validation
- Can you name 10 customers? (Critical test)
- Update assumptions as you learn
- Model three scenarios (pessimistic, base, optimistic)
Decision Framework:
- If SAM < $10M: Too small for most ventures
- If Year 1 SOM < $50K: Question if worth effort
- If methods disagree >5x: Assumptions need work
- If no competitors exist: Either no market OR huge opportunity (validate carefully)
Related Skills
product-positioning - Position against competitive landscapeproduct-market-fit - Validate market demand existscompetitive-analysis-templates - Analyze market attractiveness and competitive dynamics
