Tam Sam Som Calculator
Build defensible TAM, SAM, and SOM estimates with stated assumptions when pitching investors or sizing a new product bet.
Overview
TAM-SAM-SOM Calculator is an agent skill most often used in Validate (also Idea research, Grow analytics) that guides citation-backed TAM, SAM, and SOM estimates through adaptive questions.
Install
npx skills add https://github.com/deanpeters/product-manager-skills --skill tam-sam-som-calculatorWhat is this skill?
- Interactive three-tier framework: TAM (100% demand), SAM (serviceable), SOM (obtainable)
- Adaptive questioning instead of a single back-of-napkin number
- Structured for citations, economic projections, and population data
- Explicit assumptions, methods, and caveats for executive and investor scrutiny
- Use cases: product idea sizing, business case, budget approval, PMF validation
- Three-tier TAM/SAM/SOM framework
Adoption & trust: 1.2k installs on skills.sh; 5k GitHub stars; 2/3 security scanners passed (skills.sh audits).
What problem does it solve?
You need market size numbers for a pitch or business case but only have a vague guess and no documented assumptions.
Who is it for?
Solo founders and PMs sizing a new SaaS or product line before build or fundraise conversations.
Skip if: Deep financial modeling in Excel only, pure engineering tasks, or markets where you refuse to state assumptions publicly.
When should I use this skill?
Sizing a market for a product idea, business case, or executive review with explicit assumptions and caveats.
What do I get? / Deliverables
You leave with tiered TAM, SAM, and SOM figures, methods, caveats, and citations sturdy enough for executives or investors to stress-test.
- TAM/SAM/SOM estimates with methods
- Assumption and caveat list
- Citation-backed market narrative
Recommended Skills
Journey fit
Spans multiple journey phases - primary shelf plus alternate fits below.
Market sizing is the canonical Validate shelf move—you prove the opportunity is big enough before you commit build budget. Scope subphase covers how large the problem market is and what slice you can realistically serve, which is exactly TAM/SAM/SOM.
Where it fits
Estimate total demand for a niche B2B tool before picking a vertical to prototype.
Bound SAM by geography and segment so the MVP scope matches a believable obtainable slice.
Sanity-check revenue ceilings implied by SOM against planned price points.
Recompute SOM after twelve months of activation data to set next-year growth targets.
How it compares
Use instead of a single ChatGPT market-size paragraph with no SAM/SOM constraints or sources.
Common Questions / FAQ
Who is tam-sam-som-calculator for?
Product managers and indie builders who must defend market size in investor meetings, budget reviews, or PMF checks.
When should I use tam-sam-som-calculator?
In Idea/research when exploring an opportunity, in Validate/scope before committing build, and in Grow when revisiting obtainable share after traction.
Is tam-sam-som-calculator safe to install?
It is conversational research guidance; review the Security Audits panel on this Prism page and verify any cited data yourself before external decks.
SKILL.md
READMESKILL.md - 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) --- ### Facilitation Source of Truth Use [`workshop-facilitation`](../workshop-facilitation/SKILL.md) 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,