Many consulting candidates prepare for case interviews like a written exam: they read casebooks, learn structures, redo calculations on their own. Then, on the day of the interview, they discover a very different exercise: speaking out loud, thinking while being watched, being interrupted, prompted, contradicted. Progress comes from cases played with a partner, and the quality of that partner matters a lot. This article explains why solo practice is not enough, where to find a partner, how to play the interviewer, what to note in the feedback and how to know you are ready.
Why practising alone is not enough
Reading a solved case gives the illusion of mastering it. You follow the reasoning, understand the structure, check the calculations. But a case interview draws on skills that reading does not train.
Talking while thinking. You have to structure your thoughts out loud, clearly, without losing the thread. It is a skill to be worked on, like a foreign language.
Managing the interaction. The interviewer asks questions, gives information drop by drop, redirects, contradicts. BCG describes the case interview, on its preparation page 🔗, as an exchange in which the candidate must ask thoughtful questions and communicate their reasoning clearly.
Calculating under pressure. A calculation done alone on paper has nothing to do with the same calculation done out loud in front of someone who is waiting.
Getting an outside view. Alone, you do not see your verbal tics, your overlong structures, your silences. A partner spots them in one session.
Firms themselves push in this direction. BCG recommends to its candidates, on its school pages 🔗, to attend its preparation workshops, to contact alumni of their school at the firm and to practise alone or in groups with the resources it provides.
Finding a partner
A good partner is someone motivated, regularly available and able to play the interviewer seriously. Several pools exist.
School consulting clubs. Most grandes écoles have a club or association dedicated to consulting, which organises practice sessions, partnerships with firms and introductions between students. It is the most natural source.
Junior-Entreprises. Their members often prepare for the same processes and are used to teamwork.
Firms’ workshops. Firms organise case preparation workshops on campus and online. They let you play cases with consultants, and meet other candidates.
Alumni of your school. A former student who has become a consultant may agree to give you a case, especially if you ask politely and precisely. These sessions are worth their weight in gold, because they reproduce real conditions.
Online platforms and communities. They let you find partners from other schools and cities, and vary styles.
The ideal is to have two or three regular partners at different levels: a partner at the same level for frequent practice, a more advanced partner or a consultant for check sessions.
Playing the interviewer
Playing the interviewer is as formative as playing the candidate. You understand what the interviewer sees, and you learn from other people’s mistakes.
To play this role well:
- prepare the case in advance: read the prompt, the data, the questions and the solution, so you can answer the candidate’s questions without hesitating;
- do not give everything at once: reveal data only when the candidate asks for it or at the point the case provides;
- play the style of the target firm: more guided, with a succession of questions, as in the sample cases McKinsey publishes on its interviewing page 🔗; more open, letting the candidate drive, as in the cases often described at BCG;
- prompt and contradict: “Why are you starting there?”, “Are you sure about that figure?”, “What would you recommend to the chief executive tomorrow morning?”;
- keep time: a case generally lasts twenty to thirty minutes; stop it at the planned time, even if it is not finished;
- take notes during the case, on what works and what does not.
Giving useful feedback
Feedback is the most valuable part of the session, and often the most rushed. Good feedback is precise, structured and action-oriented.
A simple grid helps structure it:
| Criterion | Questions to ask | |---|---| | Structure | Was the structure built for the case? MECE? Prioritised? | | Analysis | Were the right data requested? Are the conclusions drawn correct? | | Calculations | Correct? Talked through? Interpreted? | | Synthesis | Did the conclusion answer the question? Was it quantified? | | Communication | Clear, calm, listening? Any verbal tics? | | Time management | Did the case progress at the right pace? |
For each criterion, give an example from the session: “When sizing the market, you forgot to convert months into years; you noticed it yourself, which is good.” End with two points to work on as a priority, not ten.
The candidate, for their part, should note this feedback in a log, to measure their progress from one session to the next.
Varying the types of case
Effective practice covers the main families of cases, not only those you are comfortable with.
- Profitability, the great classic, developed in our article on the profitability case.
- Market sizing, which tests assumptions and calculation.
- Market entry or product launch.
- Merger or acquisition, with a valuation and synergies component.
- Growth, organic or external.
- Operations cases, on a plant, a supply chain or a process.
- Public sector or non-profit cases, which change the objectives.
Also vary industries and formats: guided cases, open cases, written cases, data-heavy cases. And work separately on the cross-cutting skills: structure (our article on case interview frameworks) and calculation (the article on mental arithmetic in interviews).
Knowing when you are ready
There is no magic number of cases to do. A few signs show that you are approaching the expected level:
- you build a case-specific structure in two minutes, without reciting;
- your calculations are correct and talked through, even under pressure;
- you always conclude with a quantified recommendation, even when time is short;
- your partners no longer find major errors, only details;
- a consultant or an alumnus gives you a case and tells you that you would get through.
Conversely, if you keep making the same mistakes after several sessions, change method: a new partner, another type of case, feedback from a consultant.
Do not forget the other half of the interview: questions about your background and motivation, detailed in our article on the fit interview. Your partners can also make you practise them, using your CV. The strategy consulting intern CV template in fact shows how a responsibility in a case club can appear on a CV. To format yours quickly, the ConseilCV editor takes care of the layout and produces a PDF that screening software can read.
Frequently asked questions
How many cases should you do before an interview?
It depends on your starting point and regularity. What matters is measurable progress from one session to the next, and feedback from an experienced partner, more than the number.
Should you practise in English?
Yes, if part of the interviews may take place in English. Do at least a few complete cases in English, because vocabulary and fluency need their own practice.
Is a less advanced partner useful?
Yes, especially when you play the interviewer: explaining and correcting help you progress. But also keep sessions with more advanced partners to be pushed.
Can you practise usefully on your own?
Yes, as a complement: reading cases, mental arithmetic, written structures, recording yourself solving a case out loud. But nothing replaces the exchange with an interviewer.
Sources
- Boston Consulting Group, Case interview preparation 🔗
- Boston Consulting Group, HEC Paris school page, interview preparation 🔗
- McKinsey & Company, Interviewing at McKinsey 🔗