Preparing for a Case Interview: Consulting

A case interview presents a business scenario (a company losing market share, a new market entry decision, a profitability decline) and you work through it with the interviewer by asking clarifying questions, structuring your analysis, performing calculations, and recommending a course of action. McKinsey uses interviewer-led cases (they guide you through specific questions). Bain and BCG use more candidate-led cases (you drive the analysis). Most firms conduct 2-3 case interviews per round with 2 rounds (6 total cases). Each interview also includes 10-15 minutes of behavioral fit questions.

Five case types cover 80% of interviews. Profitability: revenue is down or costs are up, diagnose the root cause and recommend solutions. Market entry: should the client enter a new market or launch a new product? Analyze market attractiveness and competitive positioning. M&A: should the client acquire a target company? Evaluate strategic fit, synergies, and valuation. Pricing: how should the client price a new product? Consider costs, willingness to pay, competition, and value. Growth strategy: how can the client grow revenue? Explore organic growth, adjacencies, and geographic expansion. Practice 20-30 cases across all types.

Foundational frameworks: profitability framework (Revenue minus Costs, then segment each), 3 C's (Company, Customers, Competitors), Porter's Five Forces (industry attractiveness), 4 P's of marketing (Product, Price, Place, Promotion), and the market sizing approach (top-down or bottom-up estimation). These frameworks provide starting structures, but interviewers expect you to customize them to each specific case. Saying I will use the profitability framework is a red flag. Instead: Given that the client's revenues are declining, I would like to explore three areas: first, whether the decline is volume or price driven, second, which customer segments are affected, and third, what competitors are doing differently.

Top candidates create a bespoke structure for each case by asking: What are the 3-4 key questions I need to answer to solve this problem? This produces a tailored, MECE (mutually exclusive, collectively exhaustive) framework that impresses interviewers. Example for a restaurant chain profitability case: (1) Revenue analysis: traffic versus check size, by location and daypart, (2) Cost analysis: food costs, labor, rent, comparing underperforming vs. performing locations, (3) External factors: competition, market trends, economic conditions, (4) Operational efficiency: menu optimization, waste reduction, staffing models. This demonstrates thinking from first principles rather than memorization.

Case interviews require real-time calculations without a calculator. Essential skills: percentage calculations (15% of 840 million), division of large numbers (3.2 billion divided by 400,000), compound growth (grow 10% annually for 5 years), and break-even analysis (fixed costs divided by contribution margin). Practice with flash cards or math apps (Magoosh, Victor Cheng's math drill) for 15-20 minutes daily. Common mistakes: calculation errors under pressure and spending too long on arithmetic. Round aggressively: 3.2 billion divided by 47 becomes 3.2 billion divided by 50 equals 64 million. Interviewers value speed and accuracy over false precision.

Estimation questions: How many gas stations are in the US? How much revenue does a Starbucks location generate per year? How many tennis balls fit in this room? Approach: break the question into component parts, state your assumptions clearly, calculate step by step, and sanity-check the final number. Example: US gas stations. 330 million people, roughly 220 million cars, each fills up once per week. A gas station serves approximately 250 cars per day. 220 million weekly fills divided by 7 days divided by 250 cars per station equals approximately 125,000 stations. Actual: 145,000. Close enough for an estimation question. Interviewers evaluate your structure and logic, not your answer's decimal precision.

Case practice must be done with a live partner (not alone reading case books). Find practice partners through: your university's consulting club, PrepLounge (free case matching with other candidates), and friends who are also preparing. Practice 4-6 cases per week, alternating as interviewer and candidate. After each case, get 5 minutes of honest feedback on your structure, communication, math, and recommendation. Recording sessions and reviewing them reveals habits you do not notice in the moment (filler words, disorganized structures, slow math). The optimal preparation range is 40-60 cases. Below 30 is insufficient; above 80 produces diminishing returns.

McKinsey: McKinsey case collection (mckinsey.com/careers), interviewer-led format with specific questions about charts and data interpretation. Bain: candidate-led cases, emphasis on structured thinking and actionable recommendations. BCG: candidate-led, often includes creative or outside-the-box thinking. Deloitte and Accenture: may include group case discussions and written case exercises. Case in Point by Marc Cosentino (30 USD) is the most popular case book. Victor Cheng's LOMS program (free videos online) is excellent for McKinsey-style prep. Each firm's website has practice cases that reveal their specific style and expectations.

These three questions appear in every consulting interview. Why consulting: connect your specific experiences to the consulting model (working on diverse problems, rapid learning, high-impact client work). Avoid generic answers about wanting to learn. Why this firm: reference specific aspects that differentiate this firm (McKinsey's structured problem-solving, Bain's results orientation, BCG's creative strategy approach) and connect them to your values. Ideally reference a conversation with someone at the firm. Tell me about yourself: 90-second structured summary covering your background, 2-3 key experiences, and why you are here today. Practice these until they sound natural, not rehearsed.

Consulting firms assess personal experience fit through behavioral questions: Tell me about a time you led a team through a difficult situation. Describe an impact you are most proud of. Tell me about a time you failed. Prepare 6-8 diverse stories using the STAR format (Situation, Task, Action, Result). Each story should be 90-120 seconds. Include stories that demonstrate: leadership in ambiguous situations, influence without authority, analytical thinking applied to real problems, resilience under pressure, and teamwork across diverse groups. McKinsey's PEI (Personal Experience Interview) requires particularly detailed, drill-down-ready stories about specific leadership and impact moments. This guide is informational only, not career advice.