Market Sizing — TAM/SAM/SOM Calculator
Build defensible market sizing for any product, pitch deck, or business case. Top-down and bottom-up methodologies combined.
What You Get
- TAM (Total Addressable Market) — entire market if you had 100% share
- SAM (Serviceable Addressable Market) — segment you can actually reach
- SOM (Serviceable Obtainable Market) — realistic capture in 12-36 months
- Bottom-up validation — unit economics × reachable customers
- Source citations — government data, industry reports, public filings
How to Use
Tell me your product/service and target customer. I'll build the full sizing.
Example prompts:
- "Size the market for AI-powered contract review for mid-market law firms in the US"
- "TAM/SAM/SOM for a SaaS helpdesk targeting e-commerce brands doing $1M-$50M revenue"
- "Market size for automated bookkeeping for UK SMBs"
Methodology
Top-Down
- Start with total industry revenue (cite source)
- Filter by geography, segment, company size
- Apply technology adoption rates
- Result = SAM
Bottom-Up
- Count reachable customers (databases, directories, LinkedIn)
- Multiply by realistic ACV (annual contract value)
- Apply conversion rates at each funnel stage
- Result = SOM
Triangulation
Compare top-down and bottom-up. If they're within 2-3x of each other, the sizing holds. If wildly different, investigate assumptions.
Output Format
## Market Sizing: [Product/Service]
### TAM — $X.XB
[Total market calculation with sources]
### SAM — $XXM
[Filtered by geography + segment + tech adoption]
### SOM (12-month) — $X.XM
[Bottom-up: customers × ACV × conversion]
### Key Assumptions
- [Assumption 1 + source]
- [Assumption 2 + source]
### Risks to Sizing
- [What could make this smaller]
- [What could make this bigger]When to Use This
- Pitch decks and investor presentations
- Go-to-market strategy planning
- New product feasibility analysis
- Board presentations and business cases
- Competitive positioning
Pro Tip
Most founders oversize their TAM and undersize their SOM. Investors see through inflated numbers instantly. A tight, well-sourced $50M SAM beats a hand-wavy $10B TAM every time.
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