The McKinsey Case Interview: Format, PEI and How to Prepare

What is the McKinsey case interview?

The McKinsey case interview is a structured business problem that the interviewer walks you through, question by question, while you think out loud. It always sits alongside a Personal Experience Interview (PEI), so each round tests both how you solve problems and how you have behaved in real situations.

When I went through McKinsey's process, the experience part came first and set the tone for the whole conversation. A strong story earned goodwill before the case even started. A vague one meant the case had to do all the work.

How does McKinsey's case format differ from BCG and Bain?

McKinsey runs an interviewer-led format. The interviewer holds a script of three to five questions and decides when to move on, so you rarely choose the next branch yourself. BCG and Bain lean toward candidate-led cases, where you propose the structure and steer toward the data you need.

The practical consequence: in a McKinsey case, each question is graded on its own. A sloppy brainstorm or a wrong exhibit read costs you even if the overall case ends well. For the other two formats, see the BCG case interview and the Bain case interview.

The Personal Experience Interview: four dimensions

McKinsey states that it assesses connection, drive, leadership, growth and problem solving. The PEI covers the first four, and the case covers problem solving. Prep providers report that McKinsey renamed the PEI dimensions in summer 2025; they were previously called personal impact, entrepreneurial drive, inclusive leadership and courageous change. Each PEI targets one dimension, and the interviewer will keep asking follow-ups until the story runs out of detail.

1. Connection: a time you worked through a difficult situation with someone who held the opposite view, or changed someone's mind without formal authority.
2. Drive: a time you set an ambitious goal outside your comfort zone, hit obstacles and kept going.
3. Leadership: a time you brought together people with different views or backgrounds to reach a shared outcome.
4. Growth: a time you adapted to a major change or an unclear situation, or acted on tough feedback.

Prepare one rich story per dimension, plus a backup. For each, know the situation, your exact actions, what people said, what you would do differently and the measurable result. Interviewers can tell within two follow-ups whether a story is rehearsed or remembered.

Stephan's note: When I interviewed candidates myself, the weakest PEI answers described what "we" did. I wanted to hear "I". Name your own decisions, even small ones, and the interviewer can score you.

Worked example: sizing a replacement tire market

Market sizing remains a McKinsey staple, often as the first question of a larger case. Here is a fresh version of the kind of tire case I described back in 2011.

The prompt: a tire manufacturer wants to know how many replacement passenger-car tires are sold in the United States each year.

1. Clarify scope. Confirm passenger cars only, replacement tires only (new cars ship with tires already fitted).
2. Pick a driver. Number of cars on the road is the cleanest anchor. Assume about 280 million passenger vehicles.
3. Estimate replacement frequency. A tire lasts roughly 50,000 miles. At about 12,500 miles per car per year, a set lasts four years.
4. Calculate. 280 million cars x 4 tires / 4 years = 280 million tires per year.
5. Sanity check. Some drivers replace single tires after damage, others keep tires too long. These effects roughly offset, so 250-300 million is a defensible range.

A typical follow-up narrows the market to one metro area, then shifts to strategy: the client is considering buying a chain of tire and car-maintenance shops. You would then structure the acquisition question around market attractiveness, the target's position, synergies and price. Practice the arithmetic in our case interview math guide.

Why case topics vary by office

McKinsey cases often reflect the work an office actually does. Candidates in New York frequently report financial services cases, Houston leans toward oil, gas and energy, and offices in India's technology hubs see more IT and outsourcing problems. Interviewers tend to adapt cases from their own engagements because they know the details well.

Use this to your advantage. Before your interview, read up on the office's main industries and the partners' practice areas. You do not need sector expertise, though basic vocabulary (margins in banking, upstream versus downstream in oil) saves you time in the case.

Where Solve fits in the process

Before you reach any interview, McKinsey screens most applicants with Solve, a gamified digital assessment of problem solving. McKinsey states that candidates must work alone and may not use apps, websites, AI tools or prepared notes. Candidate reports describe games such as Redrock Study and Sea Wolf, with a newer version adding Sustainable Futures Lab from around March 2026.

The old paper Problem Solving Test (PST) is retired. Our McKinsey test guide covers Solve in detail. The skills the PST demanded, fast exhibit reading and clean math under time pressure, still carry straight into the case.

How I would prepare in six weeks

1. Weeks 1-2: learn three or four core frameworks and practice building MECE structures out loud.
2. Weeks 2-3: daily mental math drills, 15 minutes a day, with large round numbers.
3. Weeks 3-5: at least 15 live cases with a partner, half of them interviewer-led in the McKinsey style.
4. Weeks 4-6: write and rehearse your four PEI stories, then have a friend push you with follow-ups.
5. Final week: one mock with a former consultant, then rest.

If you want a structured plan, my book Cracking the Case covers the personal-fit interview, guesstimates and three fully worked candidate cases from start to finish.