Consulting Interviews: McKinsey, BCG, and Bain — What's Different

Consulting Interviews Are a Different Animal

If you're coming from tech or any other industry, consulting interviews will feel alien. There's no LeetCode. There's no system design whiteboard. Instead, you'll spend 30-45 minutes working through a business problem with your interviewer while they watch how your brain works.

I've coached a handful of people through MBB (McKinsey, BCG, Bain) interviews, and the number one mistake is treating the case interview like a test with a right answer. It's not. It's a conversation. And the sooner you understand that, the better you'll do.

The Case Interview: What's Actually Happening

A case interview goes something like this: "Your client is a regional airline that's been profitable for 10 years but has seen margins decline by 15% over the last two years. They've asked us to figure out why and what to do about it."

That's it. That's the prompt. Now you have to structure an approach, ask the right questions, analyze data they feed you, and arrive at a recommendation. In real time. While sounding composed and confident.

The four most common case types you'll see:

• Profitability cases — "Why are profits declining?" (Revenue side? Cost side? Both?)
• Market sizing — "How many electric vehicle charging stations will the US need by 2030?"
• Market entry — "Should this European bank expand into Southeast Asia?"
• M&A — "Our client wants to acquire a smaller competitor. Should they?"

Market sizing questions trip people up because they feel like math problems. They're not — they're logic problems. Nobody cares if your final number is exactly right. They care about whether your assumptions make sense and your structure is clean.

McKinsey's PEI Is Its Own Beast

McKinsey does something the other two don't: the Personal Experience Interview, or PEI. It takes up about half of each interview round, and it's where most people underestimate the difficulty.

PEI questions sound like standard behavioral questions. "Tell me about a time you led a team through a difficult situation." But McKinsey interviewers will drill down relentlessly. They don't want the polished STAR-method answer you rehearsed. They want to understand exactly what happened, what you specifically did, and what you were thinking at each decision point.

Here's the thing: they'll keep asking "why?" and "what happened next?" until they get past your prepared story and into the real, messy details. A friend of mine spent 25 minutes on a single PEI story because the interviewer kept pushing deeper. "But what did the other team members actually say when you proposed that? How did you handle the pushback? What would you have done differently?"

McKinsey evaluates PEI on three dimensions, and you'll get different ones in different rounds:

1. Leadership — Did you drive outcomes, not just participate?
2. Personal impact — Did you change someone's mind or behavior?
3. Entrepreneurial drive — Did you build something or take a risk?

Prepare 3-4 deep stories. I mean deep. You should be able to talk about any of them for 15-20 minutes without running out of real details.

BCG and Bain: The Fit Interview

BCG and Bain don't do PEI — they do "fit" interviews, which are shorter and less intense but still matter more than people think. These typically take 10-15 minutes at the start of each round.

"Why consulting?" and "Why BCG/Bain?" are guaranteed questions. Your answers need to be specific and genuine. "I want to solve business problems" is the consulting equivalent of "I'm passionate about technology" — it says nothing.

Better: "I spent two years in brand management at P&G and realized the problems I found most interesting were the cross-functional strategic ones, not the day-to-day marketing execution. Consulting gives me exposure to those problems across industries, and BCG's focus on digital transformation aligns with where I want to build expertise."

That's specific. It connects your past to your future. It mentions something real about the firm.

MBB vs. Tier-2: Does It Matter?

Let's be real: yes, it matters. McKinsey, BCG, and Bain have different exit opportunities than Deloitte, Accenture Strategy, or Oliver Wyman. MBB alumni networks are disproportionately powerful. A McKinsey stamp on your resume opens doors that other firms' stamps don't.

That said, the interview process at tier-2 firms is generally similar — case interviews plus behavioral. The cases tend to be slightly less abstract and more grounded in the firm's actual practice areas. And the competition is real but less insane. MBB acceptance rates hover around 1-2%. Tier-2 firms are closer to 5-10%.

If you're a career changer or coming from a non-target school, tier-2 firms can be a more realistic entry point. And plenty of people have built incredible careers at them.

The Hypothesis-Driven Approach

This is the single most important concept for case interviews, and most people don't learn it until they've already failed a few.

When you get a case, don't just start listing areas to explore. Form a hypothesis. "My initial hypothesis is that the airline's margin decline is driven by rising fuel costs and increased competition on their key routes, putting pressure on both the cost and revenue side."

Then test it. Ask for data. Confirm or refute each part. Adjust your hypothesis as new information comes in. This is exactly how consultants work on real engagements, and interviewers are specifically watching for it.

The opposite approach — "Let me look at revenues, then costs, then market trends, then competitive landscape" — is what they call "boiling the ocean." You're analyzing everything instead of thinking about what matters most. That's a fail signal.

Real Case Question Examples

Here are actual case prompts similar to what you'd see in MBB interviews:

Type	Prompt
Profitability	"A national grocery chain has seen same-store profits drop 20% despite revenue staying flat. What's going on?"
Market entry	"A German auto parts manufacturer wants to know if they should build a factory in Mexico. Advise them."
Market sizing	"Estimate the annual revenue of all food trucks in New York City."
M&A	"A private equity firm is considering acquiring a chain of urgent care clinics. Should they proceed?"

For the market sizing example, here's how you'd structure it: estimate the number of food trucks (population of NYC × percentage of blocks with food trucks, or work backwards from permits issued), multiply by average revenue per truck per day, multiply by operating days per year. Each assumption should be stated clearly so the interviewer can course-correct you if you're way off.

How to Actually Prepare

Case prep is like learning an instrument. Reading about it does almost nothing. You have to practice out loud, ideally with another person.

• Do 30-50 cases before your first real interview. Sounds like a lot. It is. But cases 1-10 will feel terrible, 10-20 you'll start finding your groove, and by 30+ you'll recognize patterns.
• Practice with partners — Find someone else prepping for consulting. Take turns being interviewer and interviewee.
• Use real casebooks — Harvard, Wharton, Kellogg, and INSEAD all publish free casebooks. Use them.
• Get comfortable with math — You'll need to do mental math and work with charts. Practice percentages, growth rates, and back-of-the-envelope calculations.
• Time yourself — Real cases run 30-40 minutes. Don't spend 15 minutes just on structuring.

If you can't find a case partner, Craqly's AI interview tool can run you through case-style interviews and give you feedback on your structure, hypothesis, and communication — it's not the same as a real person, but it's a lot better than practicing alone in front of a mirror.

Consulting interviews reward preparation more than almost any other type. The people who get offers aren't necessarily the smartest — they're the ones who practiced the most deliberately.