AI Prompt for Market Sizing (TAM SAM SOM)

AI prompt for TAM SAM SOM: structured market sizing with assumptions to defend. Free model. Copy it into ChatGPT, fill in the brackets, and publish.

The prompt

You are a market sizing analyst who shows their work.

CONTEXT: Business/product: [PRODUCT]. Target customer: [TARGET_CUSTOMER]. Geography: [GEOGRAPHY]. Price point: [PRICE_POINT]. Known data points: [KNOWN_DATA].

TASK: Build a TAM / SAM / SOM sizing model for [PRODUCT].

FORMAT:
1. TAM (Total Addressable Market): top-down estimate with the math shown step by step.
2. SAM (Serviceable Addressable Market): narrow TAM by [GEOGRAPHY] and [TARGET_CUSTOMER] fit, math shown.
3. SOM (Serviceable Obtainable Market): realistic 3-year capture with assumptions stated.
4. Bottom-up check: ([TARGET_CUSTOMER] count × [PRICE_POINT] × penetration) — compare with top-down and explain gaps.
5. Assumption table: every key assumption, its value, confidence (high/med/low), and how to validate it.
6. Two scenarios: conservative and optimistic SOM.

CONSTRAINTS:
- Show ALL math. A number without its calculation is worthless.
- Label every figure: fact (sourced), estimate (reasoned), or guess (flagged).
- Never present a single "the market is $X" without ranges.
- SOM must be defensible to a skeptical investor — no "1% of a huge market" logic.
- Plain language; define TAM/SAM/SOM briefly at the start.

Variables to fill in

Replace each [variable] in the prompt with your own details:

[PRODUCT] [TARGET_CUSTOMER] [GEOGRAPHY] [PRICE_POINT] [KNOWN_DATA]

Example input

PRODUCT='scheduling software for salons', TARGET_CUSTOMER='independent salons and spas', GEOGRAPHY='US', PRICE_POINT='$59/month', KNOWN_DATA='~80,000 salons in the US per industry association'

How to use this prompt

Use this for pitch decks and planning, but replace AI estimates with real data where flagged low-confidence. Investors probe assumptions — the assumption table is your defense.