Market Sizing: Estimate Anything Under Pressure
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.
What's included
- Live, timed market sizing reps — not worked examples on paper
- A repeatable method for choosing your approach in the first fifteen seconds
- Defensible assumptions and the sanity check that separates strong answers from average ones
- Feedback from a former McKinsey interviewer on where you actually lost points
Meet your expert
Ben L.
• Stanford GSB Alum, Class of 2021 -- see relevant background & experience below: • Coaching | Advised 400+ admits into Stanford GSB, HBS, Wharton, Kellogg, MIT Sloan, INSEAD, Haas, and more (see ~100 Leland reviews), while teaching multiple courses through Leland • What I'm Doing Now | Based in NYC, building a publication 'Staying Human', working on a stealth, marketplace startup, coaching and playing chess profssionally, and advising a slate of Seed to Series C startups through Elevate LLC • Public Policy | Prior to Stanford, worked on the Policy Team for the Chicago Mayor's Office under Mayor Rahm Emanuel, focusing on 5G infrastructure policy, criminal justice policy, and citywide corporate/economic development deals • McKinsey | Before policy, worked at McKinsey & Co , with casework focused on job training for the formerly incarcerated and workforce development for at-risk youth • PE / VC / Startup Advising | After Stanford, worked in Bain's Private Equity Group on various due diliegences, managed deals with several venture capital firms, and advised multiple startups on growth and go-to-market strategy • Professional Writing | Speechwriting in public policy & political environments, Lead Editor for Nondisclosure (Stanford GSB's magazine) and Managing Editor for the Stanford International Policy Review • Additional Writing | Crafting op-eds, ghostwriting for major publications, developing a fictional short story collection, policy deep dives, a book on chess applications to life, and application essays of all sorts • GMAT / Test-Taking | Scored in the highest percentile of GMAT test-takers, but more importantly I've honed my ability to help others extrapolate top test-testing strategies in the areas they're weakest • Additional Coaching Details | 5+ years experience working with >750 individuals on essay writing and resume professionalization for top consulting firms, MBA programs, execs, and the broader job market • Interview Training | I was interview-trained with McKinsey, helping me give high-quality mock interviews for MBBs and any MBA program; I've also held 10+ events through Leland on interview prep for McKinsey's PEI and GSB's interview process in particular