What Is a Case Interview? The Complete Undergrad Guide

"What is a case interview, and is it something you can actually prepare for?" That's the question, almost word for word, that a sophomore typed into a first message to WSG last fall after a Bain information session. She'd left the session knowing that the interview involved "a business problem" and nothing else, and she was trying to decide whether to spend her spring on it.

I'm Stephen Turban, founder of WSG. I went through McKinsey's case interviews as a candidate, then worked there, and I now coach undergrads through the process at all three MBB firms and the tier 2 shops. The short answer to her question is yes. A case interview is one of the most learnable interviews in professional recruiting, because the firms tell you exactly what they're testing and the format barely changes from year to year.

This guide explains what a case interview is, walks through one minute by minute with a full worked example, lists what interviewers score, and lays out how to prepare for it as an undergrad.

Once the format makes sense, the next step is getting practice cases in, and these free prep resources, along with how to actually use them, are collected here. When you start doing live cases with a partner, keep these tips for avoiding the most common first-timer mistakes here close by.

How long is a case interview?

A single case runs 25 to 35 minutes inside a 45-minute interview that also includes a fit or behavioral section. At McKinsey, BCG, and Bain, a first round typically consists of two back-to-back interviews (each featuring a separate case and fit question with a consultant or engagement manager). A final round involves two to three separate interviews led by Partners, followed by an immediate decision. A case interview is short, and the structure you build in the first two minutes decides most of it.

What are case interviewers actually looking for?

Five things: whether you can break a vague problem into a few clear pieces, whether you can do arithmetic under pressure without losing the thread, whether you find the non-obvious driver, whether you communicate in a way a partner could repeat to a client, and whether you stay composed when the interviewer pushes back. Interviewers aren't looking for the right answer, because most cases don't have one; they're looking for how you get to an answer.

1. A case interview is a simulation of the first two weeks of a consulting project

Here's what a case actually is. The interviewer plays a client, or a partner relaying a client's question. The question is a real business problem, usually simplified: "Our client is a regional grocery chain whose profits have fallen 15 percent in two years. What's going on and what should they do?" You have no slides, no laptop, and a piece of paper. Over the next half hour, you and the interviewer work the problem together, with the interviewer handing you data as you ask for it and occasionally steering.

Firms interview this way because the case reproduces the job. A first-year consultant spends their days taking a big, messy question from a client, splitting it into pieces a team can work on, running numbers on the pieces, and turning the result into a recommendation someone senior will present. The case is that loop compressed into thirty minutes.

Who uses it: McKinsey, BCG, and Bain, every tier 2 strategy firm (Oliver Wyman, L.E.K., Kearney, Roland Berger, Strategy&), the Big 4 strategy practices (Monitor Deloitte, EY-Parthenon), boutiques like ZS and Putnam, and, in a more quantitative form, the economic consulting firms. A few investment banks and private equity firms use short case studies in final rounds, but the format below is the consulting one.

A case interview is a working session, not a quiz, and the interviewer is scoring how you'd behave on a real project.

2. There are two formats, and knowing which one you're in changes what you do

Cases come in two styles, and the firms are open about which one they use.

Interviewer-led, which is McKinsey's format. The interviewer moves you through a pre-set sequence of questions: "How would you structure this?" then "Here's an exhibit, what do you see?" then "What would you estimate for X?" then "What would you recommend?" You still need to build a structure and drive within each question, but the interviewer controls the order. Interviewer-led cases reward precision on each step and a clear answer-first style.

Candidate-led, which remains the default BCG format, the final-round partner format at Bain, and the common standard across tier 2 firms. After the prompt and your structure, you drive: 'I'd like to start with revenue, specifically isolating same-store volume vs. price changes.' (Note: Bain has shifted many first-round cases toward standardized interviewer-directed questions, so candidates must be ready to drive or pivot when prompted).

The practical difference: in an interviewer-led case, when you're handed a question, answer it fully and stop, because the next one is coming. In a candidate-led case, every time you finish a piece of analysis you have to say what it means and where you're going next, or the case stalls and the interviewer marks you down for it.

Interviewer-led cases score how well you answer the question in front of you; candidate-led cases score whether you know which question to ask next.

3. The anatomy of a case, minute by minute

Most cases follow the same sequence. Here it is with rough timing for a 30-minute case.

• Minutes 0 to 2, the prompt. The interviewer reads the situation and the question. Write down the key facts and the exact question. Repeat the question back in one sentence to confirm you understood it.

• Minutes 2 to 4, clarifying questions. Ask two or three clarifying questions, never ten. What does the client mean by "profit" (operating profit, margin, absolute dollars)? What's the time frame? Does the client have a preference or constraint you should know about? Then ask for a minute to structure.

• Minutes 4 to 7, the structure. Take about 60 to 90 seconds of silence to write your structure, then walk the interviewer through it. For example: "I'd split this into three areas. First, whether the decline is revenue or cost. Second, within whichever it is, which line moved. Third, what's driving that line, internal or external." Say where you'd start and why.

• Minutes 7 to 20, the analysis. You ask for data; the interviewer gives you an exhibit (a chart or table). You read it out loud, say what stands out, do the math, and state what it means for the question. Two or three exhibits is typical. Somewhere in here the interviewer will ask you to estimate something or brainstorm a list.

• Minutes 20 to 25, the twist. Many cases introduce a new fact late ("the client just learned a competitor is cutting prices 10 percent"). The test is whether you can fit it into your structure without starting over.

• Minutes 25 to 30, the recommendation. The interviewer says "the CEO just walked in, what do you tell her?" You give a one-minute answer: recommendation first, two or three reasons with numbers, the main risk, and the next step.

Every case has a prompt, a structure, two or three exhibits, one twist, and a recommendation, and rehearsing that shape is most of the preparation.

4. A full worked case, with the numbers

Here's a profitability case the way a strong undergraduate candidate would run it, in a candidate-led format. The client is a regional gym chain, 40 locations, and its profits fell from $20 million to $15 million over two years. The interviewer asks why and what to do.

Clarifying: "Is the $5 million decline in operating profit, and is it spread across locations or concentrated?" The interviewer says operating profit, and that the client doesn't know how it's distributed. "Has the number of locations changed?" Two new locations opened last year.

Structure: "Profit is revenue minus cost, so first I'd find out which one moved. On revenue, I'd look at members times average monthly fee, and I'd separate the 38 existing gyms from the two new ones. On cost, I'd look at the big lines: rent, staff, equipment, and marketing. Then I'd look at whether the cause is something the client did or something in the market. I'd like to start with revenue, since a member count drop would be the most common story in this industry."

The interviewer hands over an exhibit: total revenue was $100 million two years ago and $104 million last year. Members grew from 200,000 to 210,000 (+5%), while revenue grew from $100 million to $104 million (+4%). That implies average revenue per member edged down slightly from 500to~495, but top-line growth remains healthy. If profit fell by $5 million while revenue increased by $4 million, total costs must have surged by 9million(104M revenue – $15M profit = $89M cost, up from $80M). The problem is entirely on the cost side. Let's isolate which cost lines expanded.

Second exhibit: rent went from $30 million to $32 million, staff from $35 million to $40 million, marketing from $5 million to $7 million, everything else flat. "Staff is the biggest move, up $5 million, or about 14 percent, while members grew 5 percent. Marketing is up 40 percent. I'd want to know whether the staff increase is at the two new gyms or across the base." The interviewer says the two new gyms together cost $3 million of staff and $1.5 million of rent, and they generated $3 million of revenue combined.

Math: "So the two new gyms lost about $1.5 million on staff and rent alone before any other costs, and they explain part of the decline but not all of it. Excluding them, staff at the existing 38 gyms still rose about $2 million on flat membership per gym. That's either wage inflation or overstaffing." The interviewer says the client raised trainer wages 8 percent to retain staff.

The twist: "The client is considering closing the two new gyms. What do you think?" The candidate: "Not yet. They're a year old, and gyms typically take a couple of years to fill. I'd want their membership ramp versus the older gyms at the same age. If they're tracking to break even by year three, keep them and fix the base. If they're behind the historical ramp, closing them saves about $1.5 million a year immediately."

Recommendation: "The profit decline has two causes. About $1.5 million is the two new gyms running below scale, which is expected and should be judged against their ramp, and about $3.5 million is cost growth in the existing base, mainly an 8 percent wage increase and a 40 percent jump in marketing that didn't produce member growth beyond 5 percent. I'd cut marketing spend back toward the prior level unless the client can show it drove the new members, review staffing ratios at the base gyms since members per gym are flat, and give the new locations until their second anniversary before deciding. The risk is that cutting marketing slows the membership growth that is working, so I'd test it in a few markets first."

That's a case. The candidate found the branch (cost, not revenue), found the line (staff and marketing), separated two causes, sized each with the numbers given, handled the twist without abandoning the structure, and closed with a recommendation that had a number, a risk, and a next step. A strong candidate doesn't recite a framework, pretend to know the industry, or offer a solution before finding the cause.

A good case answer finds the branch, finds the line, sizes it, and recommends something specific with a risk attached.

5. The five case types, and why knowing them speeds everything up

Nearly every undergraduate case is one of five kinds, and recognizing which one you've been given in the first thirty seconds tells you which structure to start from.

• Profitability. "Profits are down, why?" Revenue minus cost, then drill.

• Market entry. "Should we enter this market?" Is the market attractive, can we win, does the math work.

• M&A. "Should we buy this company?" Why, what it's worth, synergies, risks, alternatives.

• Operations. "Our costs are above the industry's. Where?" Follow the product through the value chain.

• Market sizing. "How many X are there?" Top-down or bottom-up estimation with stated assumptions.

Interviewers mix the types: a market entry case often contains a market sizing step, and an M&A case contains a profitability analysis of the target. The type tells you where to start, and the case tells you where to go.

Identify the case type in the first thirty seconds, start from its structure, then rebuild the structure to fit the client.

6. Mental math and exhibits are where prepared candidates separate from unprepared ones

The math in a case is never hard; it's percentages, multiplication of round numbers, and breakevens. It feels hard because you're doing it out loud, in front of someone, while trying to remember what the number is for.

Two habits fix it. First, round before you calculate and say that you're rounding. "$104 million over 210,000 members, call it $100 million over 200,000, so about $500 per member." The interviewer wants the approach, and a rounded number that's clearly labeled beats an exact one you fumble. Second, always attach the result to the question. "$495 per member, down about 1 percent" is a number. "So revenue per member is essentially flat, so the problem isn't pricing" is an insight.

Exhibits follow a routine. Read the title and the axes out loud. State the one or two things that stand out ("the new gyms are one twentieth of revenue and one eighth of staff cost"). Then say what it means for your structure. Candidates who describe every bar on the chart run out of time; candidates who name the one thing that matters move the case forward.

Round the numbers, label what you're doing, and end every calculation with what it means for the client.

7. The recommendation is graded on its first sentence

The end of a case is a compressed version of what a partner does in a client's office: answer the question in the first sentence, then support it. The format that works, in about 60 seconds:

• The recommendation. "I'd recommend the client keep the new gyms for now and cut base costs."

• Two or three reasons, with numbers. "First, $3.5 million of the decline is cost growth in the existing gyms. Second, the new gyms are on a normal ramp."

• The main risk. "The risk is that marketing cuts slow growth."

• The next step. "I'd test the marketing cut in a few markets and pull the new gyms' ramp data."

The failure I see most often is a recommendation that arrives after a minute of summary. "So, we looked at revenue, and revenue was up, then we looked at cost..." The interviewer knows what you looked at; they were there. Start with the answer.

Say the recommendation first, support it with two numbers, name one risk, and stop.

8. What's on the interviewer's scoring sheet

After the case, the interviewer fills out a form, and the categories are close to the same at every firm. Knowing them tells you what "good" looks like from the other side of the table.

1. Problem Solving & Structuring: Did you build a tailored, MECE issue tree from first principles, or recite a canned mnemonic? 

2. Quantitative Numeracy: Were calculations fast, error-free, articulated out loud, and tied back to a business takeaway? 

3. Commercial Judgment & Practical Insight: Did you spot the operational reality behind the numbers (e.g., distinguishing between new-store ramp vs. core-store wage bloat)? 

4. Executive Communication: Was your style hypothesis-driven and answer-first (Pyramid Principle), suitable for a C-suite presentation? 

5. Coachability & Presence: Did you incorporate steering cues gracefully, or become defensive under pressure?"

At the final round, the partner interview adds judgment and fit: would this person be credible with a client, and do they want to work with them. That's why the fit interview and the case carry similar weight at the end.

The scoring sheet has five lines, and the case is designed so that each of the five gets tested at least once.

9. Where the case sits in the full process

For an undergraduate applying to MBB, the sequence is: online application (opening January–March for sophomore-spring cycles, or late summer for junior cycles), followed by an automated digital assessment within 1–3 weeks, a two-interview first round, and a partner-led final round. 

The online assessments are the gate before any human interview. McKinsey Solve is an ~80-minute gamified assessment testing cognitive process and systems modeling across rotating modules like Redrock Study, Sea Wolf (Ocean Cleanup), and Sustainable Futures Lab. BCG uses the Casey Chatbot Assessment—a 25- to 30-minute interactive case simulation ending in a recorded 1-minute video synthesis. Bain screens via platforms like Sova or TestGorilla, featuring timed numerical, verbal, and logical reasoning modules, often paired with recorded video situational responses. They're pass/fail, they're different from a live case, and each one has its own preparation, which the firms describe on their careers sites.

The first round is typically one case and one fit interview, with a consultant or manager. The final round is two or three cases and a partner conversation, often on the same day. Some firms run the whole thing in a few weeks; others spread the rounds across a semester.

The live case is the middle of a four-stage process, and the assessment before it cuts more candidates than the case does.

10. How to prepare as an undergrad: partners, a schedule, and the firms' own materials

Three months before your first interview is the right time to start seriously. Here's the plan that works for the students I coach.

Learn the format first. Read the case preparation pages the firms publish, because they describe what their interviewers score and include practice cases: McKinsey's official “Interviewing with Us” page, BCG's case interview preparation, and Bain's case interview guidance.  Case in Point by Marc Cosentino is the standard book for structure; Victor Cheng's Case Interview Secrets is useful for the mindset of thinking rather than reciting, though some of its material is dated.

Then practice live. Two to three cases a week with a partner, alternating who plays the interviewer, for two to three months. A consulting club is the easiest place to find partners. Use your campus consulting club or platforms like PrepLounge for live peer-to-peer mocking. The firms' own published cases and platforms like Crafting Cases or RocketBlocks provide clean prompts for partners to administer. 

Drill math on your own. Ten minutes a day of percentages, large multiplications, and breakeven calculations. Ten minutes of daily math is the highest-return ten minutes in the plan.

Record one case a week and watch it. Most candidates discover that they talk for too long before structuring, or that they read exhibits without concluding anything, and both are fixable once you've seen yourself do it.

Finally, do the fit interview prep alongside the cases. Three stories with situation, action, and measurable result, and a two-sentence "why consulting" and "why this firm." The final round weighs these as heavily as the case.

The sophomore who typed the question at the top of this guide spent her spring doing exactly that: a semester of cases with two partners from her consulting club, math every morning, and the firms' own materials as the spine. She had a Bain first round in April and a final round in May, and she'll be an Associate Consultant Intern next summer. A case interview is a learnable format with a known structure and a public scoring sheet, and an undergrad who practices it live for three months walks in knowing what's about to happen.