icp-buying-center-builderlisted

# ICP & Buying-Centre Builder Two mistakes account for most broken ICPs: sizing against the wrong market number, and defining "ideal customer" at the wrong altitude. ## Inputs to gather **Required:** - Your current ICP definition, even if informal ("companies like X") — there's always a starting point to sharpen **Helpful, not blocking:** - A short list of your best-fit customers (5-10 is enough) and why they're a good fit - A CRM export of closed-won and closed-lost deals, if available — win-rate patterns by segment are the fastest way to find the real buying centre - Any intent-data or firmographic tooling already in use (tells you what signal layer you already have vs. need) **If none of this is available:** default to the internal method — ask *"who are your five best customers right now, and what do they have in common at the department level, not just the company level?"* That single question usually surfaces the buying centre. ## Fix 1 — size against what's actually obtainable Use the standard sizing funnel, but plan against the right layer of it: - **Total market** — every possible buyer, anywhere, ever. Useful for long-range strategy only. - **Serviceable market** — the slice reachable given your current product, geography, and channel. - **Obtainable market** — the slice you can realistically win given competition, current share, and resourcing. **The rule:** plan and forecast against the *obtainable* number. Using the total-market number as the working tar