MBB Market Sizing Guide

You can get the number right and still fail the case. MBB interviewers aren't scoring your arithmetic; they're scoring whether you stated the equation before you computed, whether you caught that transactions aren't cups, whether you know an installed base from an annual sales flow and whether you finished with the business implication instead of the number. This guide is seven cases, ordered by difficulty, each written the way the question actually appears in a real interview: clarifying questions worth asking, the trap that catches the average candidate, a full worked answer, and a breakdown of what separates a strong one. You'll size: + Disposable cups at a national coffee chain + Airport throughput two independent ways + UK pet insurance + German elevator maintenance + US EV fast-charging in 2030 + An AI radiology product with no observable price + US residential HVAC