Why it matters in B2B GTM
TAM, SAM, SOM is the standard top-down framing investors expect to see, and the standard sanity check founders need before picking a wedge. Three nested numbers — global market, the part you can actually sell to today, and the part you can realistically capture in 3 years.
TAM-only thinking is dangerous. A $50B TAM means nothing if your SAM is $200M because of geography, language, or compliance constraints — and your SOM is $20M because you're competing with three well-funded incumbents.
Good market sizing is bottom-up: count the companies in your SAM, estimate the share you can win per segment per year, and roll up. Top-down "1% of a $10B market" is the answer that gets a deck rejected.
How ICPGTM uses it
ICPGTM playbooks include a sizing block for each ICP — companies in the segment, plausible penetration, and the assumptions behind both — so the pitch you tell investors and the pipeline you tell your team are grounded in the same numbers.
Related terms
- Ideal Customer Profile(ICP)
An Ideal Customer Profile (ICP) is a written description of the type of company that gets the most value from your product and is easiest for you to sell to, broken down into firmographics, jobs-to-be-done, pains, and buying triggers.
- Firmographics
Firmographics are the descriptive attributes of a company — industry, size, revenue, geography, tech stack, growth stage — that B2B teams use to segment markets and qualify accounts.
- Wedge Strategy
A wedge strategy is the deliberate choice to enter a market by serving one narrow, underserved segment exceptionally well — using that beachhead to earn trust, generate referrals, and expand into adjacent segments.
- Product-Market Fit
Product-market fit is the state where a product satisfies a strong market demand — customers buy without heroic selling, retain without heroic support, and refer others unprompted.
- Customer Acquisition Cost(CAC)
Customer Acquisition Cost (CAC) is the fully loaded cost of acquiring one new paying customer — sales salaries, marketing spend, tools, contractors — divided by the number of new customers won in the same window.
Apply this to your own product
Generate three ranked ICPs, a buyer committee, outreach drafts, and a 30/60/90 GTM plan in about 90 seconds — your first playbook is free.