harutsugu-namitsuki/tam-sam-som-calculator

Purpose

Guide product managers through calculating Total Addressable Market (TAM), Serviceable Available Market (SAM), and Serviceable Obtainable Market (SOM) for a product idea by asking adaptive, contextually relevant questions. Use this to build defensible market size estimates backed by real-world citations, economic projections, and population data—essential for pitching to investors, securing budget, or validating product-market fit.

This is not a back-of-napkin guess—it's a structured, citation-backed analysis that withstands scrutiny.

Key Concepts

TAM/SAM/SOM Framework

The three-tier market sizing model:

Total Addressable Market (TAM):

• The total market demand for a product or service
• "If we captured 100% of the market, what's the revenue?"
• Broadest possible market (no constraints)

Serviceable Available Market (SAM):

• The segment of TAM your company can realistically target
• Narrowed by geography, firmographics, demographics, or product constraints
• "Who can we actually reach with our product?"

Serviceable Obtainable Market (SOM):

• The portion of SAM you can realistically capture
• Accounts for competition, market constraints, go-to-market capacity
• "What can we capture in the next 1-3 years?"

Why This Works

• Top-down validation: TAM → SAM → SOM ensures estimates are grounded in reality
• Investor-friendly: Standard framework VCs and execs understand
• Citation-backed: Real data sources (Census, Statista, World Bank) add credibility
• Adaptive: Questions adjust based on context (B2B vs. B2C, US vs. global, etc.)

Anti-Patterns (What This Is NOT)

• Not a single-number guess: "The market is $10B" without supporting data
• Not static: Markets evolve—reassess annually
• Not a substitute for customer validation: Market size ≠ product-market fit

When to Use This

• Pitching to investors or execs (need market size in deck)
• Validating product ideas (is the market big enough?)
• Prioritizing product lines (which has bigger opportunity?)
• Setting growth targets (what's realistic to capture?)

When NOT to Use This

• For internal tools with captive users (no external market)
• Before defining the problem (market sizing requires clear problem space)
• As the only validation (pair with customer research)

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Facilitation Source of Truth

Use workshop-facilitation as the default interaction protocol for this skill.

It defines:

• session heads-up + entry mode (Guided, Context dump, Best guess)
• one-question turns with plain-language prompts
• progress labels (for example, Context Qx/8 and Scoring Qx/5)
• interruption handling and pause/resume behavior
• numbered recommendations at decision points
• quick-select numbered response options for regular questions (include Other (specify) when useful)

This file defines the domain-specific assessment content. If there is a conflict, follow this file's domain logic.

Application

Use template.md for the full fill-in structure.

This interactive skill asks up to 4 adaptive questions, offering enumerated context-aware options at each step. The agent adapts questions based on previous responses.

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Step 0: Gather Context (Before Questions)

Agent suggests:

Before we begin, it's helpful to have product context. If available, please share:

For Your Own Product:

• Website copy (homepage, product pages, value prop statements)
• Marketing emails or landing pages
• Product descriptions or positioning statements
• Case studies or customer testimonials
• Sales deck or pitch materials

If You Don't Have a Product Yet:

• Find a similar or adjacent product (competitor or analog)
• Copy their website homepage, product description, or landing page
• We'll use this as a reference point for market sizing

You can paste this content directly, or we can proceed with a brief description.

Why this helps:

• Marketing materials already contain target audience, pain points, and value props
• Analyzing real content (yours or competitors') grounds the analysis in reality
• You can benchmark against similar products' market positioning

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Optional Helper Script (Deterministic Math)

If you already have population and ARPU numbers (or a TAM estimate), you can run a deterministic helper to compute TAM/SAM/SOM and generate a Markdown table. This script does not fetch data or write files.

python3 scripts/market-sizing.py --population 5400000 --arpu 1000 --sam-share 30% --som-share 10%

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Question 1: Problem Space

Agent asks: "Based on the context you've provided (or will describe), what problem space are you exploring for market sizing?"

Offer 4 enumerated examples (user can select by number or write custom):

1. B2B SaaS productivity — E.g., "Workflow automation for small business operations" (like Zapier, Integromat)
2. Consumer fintech — E.g., "Personal budgeting app for Gen Z users" (like Mint, YNAB)
3. Healthcare/telehealth — E.g., "Mental health support for remote workers" (like BetterHelp, Talkspace)
4. E-commerce enablement — E.g., "Payment processing for online sellers" (like Stripe, Square)

Or write your own problem space description based on the marketing materials you shared.

Tip: If you provided website copy or marketing materials, the agent can extract the problem space from phrases like:

• "We help [target] solve [problem]"
• "The #1 solution for [use case]"
• Customer pain points in testimonials or case studies

User response: [Selection or custom description]

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Question 2: Geographic Region

Agent asks: "What geographic region are you targeting?"

Offer 4 enumerated options (adapted based on problem space):

1. United States — Best for detailed Census Bureau data, BLS stats, robust industry reports
2. European Union — Use Eurostat, local statistical agencies; note GDPR/compliance considerations
3. Global — World Bank, IMF data; broader but less granular
4. Specific country/region — E.g., "Canada," "Southeast Asia," "Latin America"

Or specify your own region.

User response: [Selection or custom]

Adaptation logic:

• If user selected B2B SaaS (Question 1, Option 1) → Emphasize US/EU markets (mature SaaS adoption)
• If user selected Consumer fintech (Question 1, Option 2) → Mention emerging markets (higher mobile adoption)

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Question 3: Industry/Market Segments

Agent asks: "What specific industry or market segments does this problem space relate to?"

Offer 4 enumerated options (adapted based on problem space + geography):

Example (if Question 1 = B2B SaaS, Question 2 = US):

1. SMB services sector — 5.4M businesses, $1.2T revenue (US Census, 2023)
2. Professional services (legal, accounting) — 1.1M firms, $850B revenue (IBISWorld, 2023)
3. Healthcare providers — 900K practices, $4T industry (BLS, 2023)
4. Tech/software companies — 500K firms, $1.8T revenue (Statista, 2023)

Or describe your own industry segment.

User response: [Selection or custom]

Adaptation logic:

• If Question 1 = Consumer fintech, offer consumer segments (e.g., "Gen Z 18-25," "Millennials 25-40")
• If Question 1 = Healthcare, offer segments (e.g., "Primary care physicians," "Therapists/counselors")

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Question 4: Potential Customers (Demographics/Firmographics)

Agent asks: "Who are the potential customers affected by this problem?"

Offer 4 enumerated options (adapted based on previous answers):

Example (if Question 1 = B2B SaaS, Question 3 = SMB services sector):

1. SMBs with 10-50 employees — 1.2M businesses, $400B revenue (Census Bureau, 2023)
2. SMBs with 50-250 employees — 600K businesses, $800B revenue (Census Bureau, 2023)
3. Solo entrepreneurs/freelancers — 3.5M self-employed, $200B revenue (BLS, 2023)
4. Service businesses with online presence — 2M businesses, $600B e-commerce (Statista, 2023)

Or describe your own customer segment (firmographics, demographics, income, etc.).

User response: [Selection or custom]

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Output: Generate TAM/SAM/SOM Analysis

After collecting responses, the agent generates a structured analysis:

# TAM/SAM/SOM Analysis

**Problem Space:** [User's input from Question 1]
**Geographic Region:** [User's input from Question 2]
**Industry/Market Segments:** [User's input from Question 3]
**Potential Customers:** [User's input from Question 4]

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## Total Addressable Market (TAM)

**Definition:** The total market demand if you captured 100% of potential customers in the problem space.

**Population Estimate:** [Calculated from data sources]
- **Source:** [Citation, e.g., "US Census Bureau, 2023"]
- **Calculation:** [Show math, e.g., "5.4M SMBs × $1.2T revenue = $1.2T TAM"]

**Market Size Estimate:** $[X] billion/million
- **Source:** [Industry report citation]
- **URL:** [Clickable link to source]

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## Serviceable Available Market (SAM)

**Definition:** The segment of TAM you can realistically target with your product (narrowed by geography, firmographics, product fit).

**Segment of TAM:** [User's narrowed segment from Question 4]

**Population Estimate:** [Calculated]
- **Source:** [Citation]
- **Calculation:** [Show math, e.g., "1.2M SMBs with 10-50 employees"]

**Market Size Estimate:** $[X] billion/million
- **Source:** [Citation]
- **URL:** [Link]

**Assumptions:**
- [List key assumptions, e.g., "Assumes 50% of SMBs have budget for automation tools"]

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## Serviceable Obtainable Market (SOM)

**Definition:** The portion of SAM you can realistically capture in the next 1-3 years, accounting for competition and market constraints.

**Realistically Capturable Market:** [Agent's estimation based on market maturity, competition]

**Population Estimate:** [Calculated]
- **Source:** [Citation]
- **Calculation:** [Show math, e.g., "1.2M SMBs × 5% market share (Year 1) = 60K customers"]

**Market Size Estimate:** $[X] million
- **Assumptions:**
  - [Competition assumption, e.g., "5 major competitors, market leader has 15% share"]
  - [GTM assumption, e.g., "Sales capacity: 50 customers/month in Year 1"]
  - [Conversion assumption, e.g., "10% trial-to-paid conversion"]

**Year 1-3 Projections:**
- **Year 1:** [X]K customers, $[X]M revenue (5% of SAM)
- **Year 2:** [X]K customers, $[X]M revenue (10% of SAM)
- **Year 3:** [X]K customers, $[X]M revenue (15% of SAM)

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## Data Sources & Citations

- [Source 1: e.g., "US Census Bureau (2023). County Business Patterns. URL: census.gov"]
- [Source 2: e.g., "IBISWorld (2023). Professional Services Industry Report. URL: ibisworld.com"]
- [Source 3: e.g., "Statista (2023). SMB Software Market Size. URL: statista.com"]
- [Add all sources used]

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## Validation Questions

1. **Does TAM align with industry reports?** [Compare to 3rd-party market research]
2. **Is SAM realistically serviceable?** [Can your GTM motion reach this segment?]
3. **Is SOM achievable given competition?** [Is 5-15% market share realistic in 3 years?]

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## Next Steps

1. **Validate with customer interviews:** Does the problem resonate with target segment?
2. **Benchmark against competitors:** What market share do incumbents have?
3. **Refine SOM based on GTM capacity:** Can sales/marketing support this growth?
4. **Update annually:** Markets shift—reassess TAM/SAM/SOM yearly

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**Would you like to refine any assumptions or explore a different segment?**

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Examples

See examples/sample.md for a full TAM/SAM/SOM analysis example.

Mini example excerpt:

**TAM:** 5.4M SMBs × $2,000 ARPA = $10.8B
**SAM:** 1.2M SMBs × $2,000 ARPA = $2.4B
**SOM:** 5% of SAM = $120M

Common Pitfalls

Pitfall 1: TAM Without Citations

Symptom: "The market is $50B" (no source)

Consequence: Can't defend the number to investors or execs.

Fix: Cite industry reports (Gartner, IBISWorld, Statista) with URLs.

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Pitfall 2: SOM Equals SAM

Symptom: "SAM is $5B, SOM is $5B" (assuming 100% capture)

Consequence: Unrealistic projection—no market has zero competition.

Fix: SOM should be 1-20% of SAM in Year 1-3, accounting for competition.

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Pitfall 3: No Population Estimates

Symptom: Only dollar amounts, no customer counts

Consequence: Can't build sales/marketing plans without knowing customer volume.

Fix: Always include population (e.g., "1.2M businesses" or "60K customers in Year 1").

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Pitfall 4: Static Assumptions

Symptom: TAM/SAM/SOM calculated once, never updated

Consequence: Stale data as markets shift.

Fix: Reassess annually. Markets grow/shrink, competition changes, new data emerges.

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Pitfall 5: Ignoring GTM Constraints

Symptom: "SOM is 50% of SAM in Year 1" (but no sales team)

Consequence: SOM isn't realistic given GTM capacity.

Fix: Ground SOM in GTM constraints (sales capacity, marketing budget, conversion rates).

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References

Related Skills

• skills/positioning-statement/SKILL.md — TAM/SAM/SOM informs "For [target]" segment size
• skills/problem-statement/SKILL.md — Problem space defines the market
• skills/recommendation-canvas/SKILL.md — Market sizing informs business outcome projections

Optional Helpers

• skills/tam-sam-som-calculator/scripts/market-sizing.py — Deterministic TAM/SAM/SOM calculator (no network access)

External Frameworks

• Steve Blank, The Four Steps to the Epiphany (2005) — Market sizing for startups
• Lean Startup methodology — Validate market size with experiments, not just desk research

Data Sources (For Citations)

• US: US Census Bureau, Bureau of Labor Statistics, IBISWorld, Statista
• Europe: Eurostat, local statistical agencies
• Global: World Bank, IMF, Gartner, Forrester

Dean's Work

• TAM/SAM/SOM Prompt Generator (multi-turn adaptive market sizing)

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Skill type: Interactive Suggested filename: tam-sam-som-calculator.md Suggested placement: /skills/interactive/ Dependencies: None (standalone interactive skill)