How to Use Claude for Market Sizing
The exact prompt, setup, and codes to get great results.
The Problem
Market sizing is required for fundraising and strategy but most estimates are either absurdly inflated ('$50B TAM!') or too vague to be useful for planning.
The Prompt (Copy & Paste)
Size the market for [PRODUCT/SERVICE]. What it does: [DESCRIPTION] Target customer: [WHO SPECIFICALLY] Geography: [MARKETS YOU'RE TARGETING] Price point: [WHAT YOU CHARGE] Calculate using both approaches: 1. **Top-down**: Start with industry size → narrow to your segment 2. **Bottom-up**: Number of potential customers × what they'd pay × purchase frequency For each approach, show: - The math step by step - Sources or assumptions for each number (be explicit about what's estimated vs. sourced) - Conservative, moderate, and aggressive scenarios Present: - TAM (Total Addressable Market) - SAM (Serviceable Addressable Market) - SOM (Serviceable Obtainable Market — what you can realistically capture in 3 years) Flag where the top-down and bottom-up numbers diverge and what that means.
Replace the [BRACKETED] placeholders with your specific details.
What You Get
A credible market sizing with transparent assumptions. Both top-down and bottom-up approaches with three scenarios. Investors can actually trust these numbers because you showed your work.
Prompt Codes That Help
Add these prefix codes to the start of your prompt for even better results:
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