Calculate TAM, SAM, and SOM with explicit assumptions, methods, and caveats. Use when sizing a market for a product idea, business case, or executive review.
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SKILL.md
tam-sam-som-calculator
Calculate TAM, SAM, and SOM with explicit assumptions, methods, and caveats. Use when sizing a market for a product idea, business case, or executive review.
argument-hint
[product idea] [market constraints]
intent
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.
type
interactive
theme
market-intelligence
best_for
Sizing a market for a business case an executive will question, Making your market assumptions explicit and attackable, Replacing a top-down guess with a defensible bottom-up estimate
scenarios
I need market sizing for a business case our CFO will pick apart, Our TAM number came from a slide nobody can source — rebuild it properly
estimated_time
20-40 min
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.
Input
Works best with: The product or idea being sized, and any market constraints you already know (geography, vertical, customer type).
Also useful: Pricing assumptions, comparable companies, and the audience for the numbers (investors, execs, business case).
Anything supplied with the invocation itself — text after the skill name, a pasted context dump, or an appended ARGUMENTS: line — counts as answers already given. Use it and skip whatever it covers; don't re-ask.
Arriving empty-handed? That works too. The calculator opens by asking what you're sizing and for whom, then works through method and assumptions.
Three entry modes — pick whichever matches where your evidence lives:
Bring your own numbers — you have population and ARPU figures; jump to the math (the helper script makes this deterministic)
Guided interview — up to 4 adaptive questions build the inputs with you (the default flow below)
Autonomous research — the agent builds a bottom-up, citation-backed estimate from government statistics and filings while you review the evidence (see Mode 3 in Application)
Example invocation:Size the market: AI scheduling assistant for independent dental practices, US only, $99/mo price point. — or for research mode: Research-mode market sizing: field-service dispatch software, DACH region; I have no numbers yet.
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)
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.
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
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.
Mode 3: Autonomous Research (when the user has no numbers)
When the user picks research mode — or arrives with a market and a decision but no data — run the
sizing as an investigation under the autonomous-investigation
protocol: ask at most the questions below that remain unanswered, show a 3-bullet search plan, then
build the estimate bottom-up with every figure labeled Fact / Inference / Assumption and cited.
The bottom-up recipe (from the GEOINT/DEMOINT discipline in
intelligence-collection-disciplines):
TAM: Establishment counts for the market (Census/NAICS, Eurostat/NACE,
or the national equivalent for the geography)
× employment/spend benchmarks (BLS, Eurostat, trade associations)
(validate against two independent analyst reports; if they disagree by 3x, say so)
SAM: TAM filtered by your actual constraints: geography, segment, compliance
requirements, tech prerequisites (technographics: who *can* buy you),
vendor-registration eligibility where applicable
SOM: SAM × realistic capture rate derived from competitor public filings
(their revenue ÷ their claimed customer count = deal size reality check)
Why bottom-up wins scrutiny: a top-down number ("2% of a $50B market") borrows someone else's
denominator and hides every assumption inside it. Establishment counts × benchmarks shows the math,
so a skeptical CFO can attack one assumption at a time instead of dismissing the whole slide. The
capture-rate trick grounds SOM in what incumbents actually achieve rather than hope.
Research-mode output uses the same analysis structure below, with two additions: an evidence label on
every figure, and an Assumptions to Validate list. When done, offer the standard next steps plus
a re-run option — sizing built from statistics releases rots slowly but really; re-run annually per
the fusion cadence.
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):
B2B SaaS productivity — E.g., "Workflow automation for small business operations" (like Zapier, Integromat)
Consumer fintech — E.g., "Personal budgeting app for Gen Z users" (like Mint, YNAB)
Healthcare/telehealth — E.g., "Mental health support for remote workers" (like BetterHelp, Talkspace)
Solo entrepreneurs/freelancers — 3.5M self-employed, $200B revenue (BLS, 2023)
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]
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]
---
## 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]
---
## 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"]
---
## 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)
---
## 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]
---
## Validation Questions1.**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?]
---
## Next Steps1.**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
---
**Would you like to refine any assumptions or explore a different segment?**
Examples
See examples/sample.md for a full TAM/SAM/SOM analysis example.
