Case interview prep: frameworks and practice resources

What happens in a case interview

A typical case lasts 30 to 45 minutes. The interviewer presents a business scenario, such as a retailer whose profits have fallen or a hospital system deciding whether to expand. You are expected to ask clarifying questions, structure your approach out loud, work through quantitative analysis, and deliver a clear recommendation.

Most firms use one of two formats. Interviewer-led cases, common at McKinsey, let the interviewer steer you through specific questions. Candidate-led cases, more common at BCG and Bain, expect you to drive the entire structure yourself. Knowing which format a firm uses before you walk in matters.

• Interviewer-led: McKinsey, Oliver Wyman, Roland Berger
• Candidate-led: BCG, Bain, Deloitte Strategy, LEK
• Mixed formats: Accenture Strategy, Kearney, Strategy&

Core frameworks every candidate should know

Frameworks are not scripts. They are starting points that help you organize your thinking quickly. The goal is to adapt them to the specific case, not recite them verbatim. Interviewers penalize candidates who force a generic framework onto a problem it does not fit.

Learn these six structures well enough to modify them on the fly.

• Profitability tree: Revenue minus costs, then drill into each driver. Use this for any 'profits are down' prompt.
• Market entry: Market size, competitive landscape, company capabilities, financial viability, and risks.
• Pricing: Cost-based, value-based, and competitive benchmarking. Know when each applies.
• M&A and investment: Strategic fit, financial return, integration risk, and alternatives.
• Operations and process: Inputs, throughput, outputs, and bottlenecks. Common in supply chain and manufacturing cases.
• Growth strategy: Ansoff matrix (existing vs. new products, existing vs. new markets) as a quick organizer.

How to structure your math in cases

Quantitative sections trip up many candidates, not because the math is hard, but because they rush. Most case math involves market sizing, break-even analysis, or simple percentage changes. The arithmetic rarely goes beyond multiplication and division.

State your assumptions out loud before you calculate. For example: 'I will assume the US has 330 million people, roughly 130 million households, and an average household income of around $75,000.' Interviewers want to see your reasoning, not just your answer.

Round aggressively to keep numbers manageable. If a market is 127 million people, use 130 million. Precision is less important than a clean, auditable calculation you can walk back through if challenged.

1. Write down every number you use so you can reference it later.
2. Label units at each step (dollars, units, percentage) to avoid errors.
3. Sanity-check your answer against real-world intuition before presenting it.

Practice methods that actually build skill

Reading case books is not enough. Passive reading does not build the muscle memory you need to structure a problem under pressure in real time. Active, timed practice with a partner is the most effective method.

Aim for at least 30 to 50 full cases before your first interview. Candidates targeting MBB (McKinsey, BCG, Bain) typically practice 50 to 80 cases over six to twelve weeks. Space your practice sessions rather than cramming, because retrieval practice over time builds stronger recall.

• Peer practice: Find a partner through MBA programs, consulting clubs, or platforms like PrepLounge. Give each other feedback using a structured scorecard.
• Expert coaching: One or two sessions with a former consultant can identify blind spots that peers miss. Rates in 2026 range from roughly $150 to $500 per hour.
• Solo drills: Time yourself structuring a case prompt in two minutes, then record yourself presenting the structure. Watch it back.
• Case books: Victor Cheng's Case Interview Secrets, the Vault Guide to the Case Interview, and firm-specific prep guides from BCG and Bain's own websites are all free or low cost.
• Online platforms: PrepLounge, RocketBlocks, and IGotAnOffer offer structured drills and peer matching.

The fit interview runs alongside the case

Every consulting interview includes a fit or personal experience component, usually 10 to 15 minutes. Firms assess leadership, impact, and cultural alignment. McKinsey calls this the Personal Experience Interview (PEI) and weights it heavily alongside the case score.

Prepare three to five stories using the situation, task, action, result format. Each story should demonstrate a different competency: leading through ambiguity, driving results, working across disagreement, and showing personal development. Keep each story under two minutes when spoken aloud.

Avoid vague language. Instead of 'I helped improve team performance,' say 'I restructured our weekly check-in to a 15-minute standup, which cut meeting time by 40% and surfaced blockers two days earlier on average.'

Getting real-time support during practice and live interviews

Break-In Bad includes an on-screen interview assistant that listens to the interviewer's questions and surfaces relevant prompts only you can see, even on a shared screen. For case interview practice, this means you can run mock sessions and get structural cues in real time without a partner present.

The assistant does not replace deliberate practice, but it can help you catch moments where you skip a step, such as forgetting to ask a clarifying question or jumping to a recommendation before sizing the problem. Use it as a safety net while you build your own instincts.

Building a prep timeline

Six to eight weeks is a realistic preparation window for most candidates with full-time commitments. Compress or extend based on your starting point and target firms.

Spend the first two weeks on framework fundamentals and math drills. Weeks three and four should be full case practice with a partner, two to three sessions per week. In weeks five and six, add fit story refinement and firm-specific research. Use the final week for light review and rest, not cramming.

1. Weeks 1 to 2: Learn six core frameworks, practice market sizing daily, read one case book.
2. Weeks 3 to 4: Complete 15 to 20 full cases with a partner, record and review at least five.
3. Weeks 5 to 6: Refine fit stories, research each target firm's recent projects and values, do two expert coaching sessions if budget allows.
4. Week 7 to 8: Simulate full interview conditions, timed and uninterrupted, then rest before the real thing.