How to Prepare for a Consulting Interview

When I interviewed at McKinsey, the partner across the table didn't want Porter's Five Forces. He wanted to watch me think about a business problem for 25 minutes without falling apart. Every piece of consulting interview prep either serves that goal or wastes your time.

Most candidates waste enormous time. They memorize twenty frameworks, skip mental math, treat behaviorals as an afterthought, and discover too late that an online assessment gates the whole process. Having been through MBB (McKinsey & Company, Boston Consulting Group (BCG), and Bain & Company)  recruiting myself and now coaching WSG students through it every cycle, here's the preparation plan I'd run today, organized around what interviewers actually score.

Case prep gets most of the attention, but recruiters weigh plenty else too, from the tips that actually move the needle in a case round, with the guide here, to what it takes to break into MBB in the first place, which we cover here.

How long does it take to prepare for a consulting interview?

Plan for 2–3 months of steady preparation. The WSG benchmark is roughly 30 live practice cases plus daily mental math before your first real interview, and cramming that into two weeks produces fluent-sounding candidates who collapse on follow-ups. Since recruiting timelines move quickly after you apply, do the bulk of your preparation before submitting applications.

What do consulting interviews actually consist of?

The recruiting process usually has three stages: an online assessment, one or more interview rounds, and a final round. The exact format varies by firm and office. McKinsey may use Solve before two consultant interviews and a Partner final round; BCG can include the CCA and online case before multiple case interviews; and Bain typically uses an online assessment followed by multiple case-based interview rounds.Cases and behaviorals carry roughly equal weight in the decision, whatever the folklore says. Firms explicitly evaluate candidates on problem-solving, communication, experience, motivation, and interpersonal skills, not just case performance.

1. The interview starts before any human meets you

The assessments are not formalities. McKinsey Solve is a gamified problem-solving test. BCG's online case runs as a chat with a bot named Casey, and candidates have reported invites landing within hours of applying, with 48 hours to complete. Bain screens with an online test in most offices.

The planning consequence is blunt: assessment prep has to be finished before you submit the application, because the assessment can arrive the same afternoon. Two timed practice runs in the right format, plus the mental math habit from section 4, covers it. Candidates who plan to "start prepping once I hear back" are describing a plan to fail a test they knew was coming.

2. Interviewers score structure, not framework recitation

The biggest misconception in consulting interview prep is that firms want you to memorize frameworks. They don’t. They want to see clear thinking: your ability to take a messy problem, break it into a few logical MECE areas meaning the categories don’t overlap and, together, cover the whole problem and tailor your approach to the specific business.

Here's the difference in practice. A framework answer to a declining-profits case recites "I'd look at the 4 Ps." A structured answer says: "Profit is price times volume minus cost, so I'd first find which of those three moved. Given this is an airline, I'd expect fuel or load factor, so let's start with cost." The second answer builds the tree from the business in front of you.

Memorize exactly one thing: profit equals revenue minus cost, revenue equals price times volume. Everything else you should be able to construct live, because interviewers steer cases away from memorized paths on purpose. They've heard every framework. They haven't heard you think.

3. Five case types are the entire syllabus

Every MBB and tier 2 case maps to one of five types, and preparing means running targeted reps on each, not collecting more frameworks.

• Profitability: profits are down, find out why. Drill: isolate revenue versus cost before proposing any fix, every time.

• Market entry: should the client enter a market. Drill: size the market, then ask whether the client can win it, then check the economics.

• M&A: should the client buy the target. Drill: always name the alternative use of the money before recommending the deal.

• Operations and cost reduction: margins lag peers, find the leak. Drill: walk the value chain and benchmark the biggest cost line first.

• Market sizing: how many gas stations in the US. Drill: one top-down and one bottom-up estimate of the same number, then reconcile.

Run two cases per type across your prep and the pattern recognition compounds fast. When a new case starts, your first silent question is "which of the five is this," and the structure follows from the answer.

4. Mental math is a separate muscle, and it fails first under pressure

No calculator, a partner watching, and a market-sizing multiplication standing between you and the next question. This is where prepared candidates crack, because case math is easy math performed under observation, and nobody practices performing.

Ten minutes daily fixes it. Percentages of large numbers, breakevens, growth rates compounding over three years, dividing anything by seven. Say the answers out loud, because the interview requires narrated math, not silent math. Two specific habits pay off disproportionately: round aggressively and announce the rounding ("call it 300 million"), and sanity-check every result against a known anchor before moving on.

When I ran cases at McKinsey as an interviewer-side observer, the tell for a shaky candidate was never a wrong number. It was the silence while they hid the calculation.

5. Behaviorals are half the decision, and McKinsey grades them like cases

The behavioral interview is where firms decide whether they'd put you in front of a client, and at McKinsey it's formalized as the Personal Experience Interview. The PEI probes three dimensions: personal impact, entrepreneurial drive, and inclusive leadership, and expects one deep story per dimension, told for several minutes with follow-ups drilling into exactly what you said, did, and felt at each step.

Prepare six stories total: one primary and one backup per dimension. Real ones, with named stakes, where you can answer "what did the other person say next" without inventing. The follow-ups are the test. A story that survives five layers of "and then what did you do" is worth ten polished surface anecdotes.

Bain and BCG run less formalized behaviorals that test the same things, with Bain leaning hardest on team-fit. The preparation is identical: six stories, told out loud until the details are reflexive, never scripted word-for-word.

6. Know your firm's case style, because the same skill shows differently

McKinsey runs interviewer-led cases: the interviewer walks you through preset questions, and the skill on display is crisp, complete answers to each. BCG and Bain run candidate-led cases: you drive the structure, choose what to analyze next, and the skill on display is steering the case yourself. Same underlying ability, different performance.

Practice both modes. Candidates who only trained candidate-led ramble through McKinsey's structured questions; candidates who only trained interviewer-led freeze when a Bain interviewer says "so, where do you want to go next?" One habit transfers everywhere: end every case with a 30-second synthesis, recommendation first, two supporting reasons, one risk. Bain interviewers in particular listen for that closing "so what," and it's the easiest scoring moment in the entire process to rehearse.

7. Live reps beat solo reading by an embarrassing margin

Reading case books feels like preparation and mostly isn't. The interview is a live performance with another human generating pushback, and only live practice builds that.

The progression that works: read one book for orientation (Case in Point by Marc Cosentino for breadth, or Case Interview Secrets by Victor Cheng for the no-frameworks mindset), then move to the firms' own materials, which are free and closest to the real thing. BCG publishes an interactive practice case and McKinsey posts Solve guidance and sample cases on its careers site. Then get live: PrepLounge for partner matching, your school's consulting club for weekly cases, and case walkthroughs from IGotAnOffer or Crafting Cases to study what good sounds like.

Log every case with one line: the type, what broke, what to fix next rep. Thirty logged live cases with deliberate fixes beat eighty casual ones, and both beat three hundred pages of reading.

8. The last two weeks are for sharpening, not learning

Fourteen days out, stop adding and start polishing. Two live cases per week, mental math daily, and your six behavioral stories rehearsed to a friend who interrupts. Re-read your case log and drill only the recurring breaks. The night before: logistics, one easy case for confidence, sleep. Nobody works well for five hours.

9. The four-week version, if you're starting late

Sometimes the invite arrives and the runway is gone. A compressed plan salvages more than panic does, so here's how WSG students triage a four-week window.

Week one: learn the five case types from one book, run your first four live cases badly, and start daily math. The early cases will hurt. That's the point of doing them first.

Week two: six live cases, two per weakest type, plus your six behavioral stories drafted and told out loud once each.

Week three: six more cases including two in your target firm's style, one full mock interview with case plus behavioral back to back, and the assessment practice runs.

Week four: taper. Four cases, daily math, stories to a friend who interrupts, logistics, and sleep.

That's 20 live cases in a month, which is below the 30-case benchmark and above what most of your competition does. The honest trade: a four-week candidate can reach solid on structure and math, but polish under pressure comes only from volume, so book the earliest interview slot you can defend, not the earliest one offered.

A late start is recoverable at 20 focused cases; an unfocused sprint through framework videos is not.

Say this, don't say that

Opening a case.

Don't say: "I'd like to use the profitability framework here."

Say: "Profits are down, so I want to find whether it's revenue or cost. Given this is a subscription business, my hypothesis is churn. Can I see how revenue has moved?"

Why consulting?

Don't say: "I love solving problems and working with smart people."

Say: "I ran a pricing project for my campus coffee shop and enjoyed the diagnosis more than the result. Consulting is the job where diagnosis is the work, and McKinsey's healthcare practice is where I'd want reps."

A PEI story.

Don't say: "My team had conflict, but I brought everyone together and we succeeded."

Say: "Two of our four members stopped attending in week three. I met each alone, learned one felt steamrolled in meetings, changed how we ran them, and both came back. We shipped two weeks late, and the professor told us the recovery was the best part of the project."

The plan compresses to one sentence: two or three months, five case types twice each and then live reps to 30, math every morning, six stories that survive follow-ups, both case styles, synthesis at the end of everything. Start counting reps this week, because at the top firms the deadline calendar has moved into sophomore spring , and the candidates you're competing against started counting last semester.