The Market Sizing Calculator

#SITUATION
You need a defensible market size for a pitch deck, board meeting, or internal strategy. Guesswork destroys credibility. You need a calculation where every number traces to a source or a stated assumption.

#PURPOSE
Produce a TAM/SAM/SOM analysis with explicit logic, cited sources, and a sensitivity table so the reader sees how the numbers move when assumptions change.

#EXPECTED OUTPUT

## 1. Definitions
- TAM: Total addressable market — everyone who could theoretically buy
- SAM: Serviceable available market — the segment you can actually reach
- SOM: Serviceable obtainable market — what you can realistically capture in 3-5 years

## 2. Bottom-Up Calculation (Primary)
- Unit economics: price × quantity logic
- Customer segments with count estimates and sources
- Penetration rate assumptions with justification

## 3. Top-Down Validation (Secondary)
- Industry report totals (name the report, year, page)
- Your segment as % of total
- Reconcile with bottom-up — if they diverge >3x, explain why

## 4. Sensitivity Table
| Scenario | TAM | SAM | SOM | Key Driver |
| Conservative | $X | $Y | $Z | Low penetration |
| Base | $X | $Y | $Z | Expected |
| Aggressive | $X | $Y | $Z | High penetration |

## 5. Source Log
Every number cited with: source name, publication date, URL if public, or "assumption" with rationale.

#CONTEXT
Product: {{product_desc}}
Target customer: {{target_customer}}
Pricing model: {{pricing}} (per seat, usage, tiered)
Geography: {{geography}}
Known data sources you have: {{sources_or_none}}