Description

Market sizing is the first thing most interviewers throw at you and the fastest way to lose the room. Not because the math is hard — because candidates freeze, pick a bad starting number, and then spend four minutes defending it. There is no correct answer to a market sizing question. There is only a defensible path, said out loud, at pace. That's what we drill. What we work on: (1) Picking your entry point. Top-down or bottom-up, population-based or consumption-based — the choice you make in the first fifteen seconds determines whether the rest is clean or a mess. (2) Segmenting without drowning. Where to cut the population, and just as importantly when to stop cutting. (3) Assumptions you can defend. Round numbers, stated confidently, with a reason. Interviewers do not care that your number is right. They care whether you knew it was reasonable. (4) The sanity check. Saying "that implies X per person per year, which feels high — let me adjust" is the single highest-scoring move in a market sizing question, and almost nobody does it. (5) Saying it out loud. Every rep is live, timed, and interrupted, because that's the real thing. I ran these as a McKinsey interviewer. I'll tell you where you actually lost points.