The case interview, explained
How consulting case interviews work and how to prepare: what interviewers look for, how to structure a problem, the main case types, mental maths and market sizing, and four original practice cases you can work through.
The basics
What a case interview is
A case interview is a business problem you solve out loud with the interviewer, usually in twenty to forty minutes. You are given a situation, for example a company whose profits are falling, and you work towards a recommendation. It is a conversation, not a test with one right answer: the interviewer wants to see how you think.
Consulting firms use it because it mirrors the real work: taking an ambiguous problem, breaking it down, doing the maths, and giving advice a client can act on. You do not need prior business knowledge, but you do need a clear head and structure.
What they assess
Five things interviewers look for
The flow
How to work through a case
Case types
The main types of case
Most cases are a variation on a handful of types. Recognising the type quickly helps you structure, but always tailor your approach to the specific problem.
Numbers
Mental maths and market sizing
You will do arithmetic without a calculator: percentages, growth, breakeven, and multiplying large round numbers. Practise until it is quick and accurate, and always sanity-check the result against common sense.
A worked market-sizing example (illustrative)
Question: roughly how many takeaway coffees are sold in Amsterdam on a typical working day? There is no exact answer; the point is a clear structure and reasonable assumptions.
Assume about 900,000 residents, plus commuters and visitors, so treat the daytime population as roughly 1,000,000. Suppose one in three buys a takeaway coffee on a working day, giving about 330,000 coffees. Add a share for tourists and multiple-cup buyers, say 20 percent, and you land near 400,000 takeaway coffees a day. State the assumptions clearly, and note that the answer moves with them; that transparency is what the interviewer rewards.
The numbers above are illustrative assumptions to show the method, not researched figures.
Practice
Four practice cases
Work through each one out loud: clarify the goal, build a structure, reason through it, and finish with a recommendation. Try it before reading the approach.
Case 1: Profitability
Prompt: A city bike-sharing operator in the Netherlands has seen its profit fall for two years while the number of rides has grown. The client wants to know why, and what to do about it.
How to approach it: Split profit into revenue and cost. Revenue per ride may have dropped (discounts, subscriptions, pricing) even as volume rose; on the cost side, look at maintenance, redistribution of bikes, theft and damage, and staff. Find the branch driving the fall, quantify it, then propose targeted actions.
Case 2: Market entry
Prompt: A Scandinavian chain of premium coffee bars is considering entering the Dutch market. Should it, and if so, how?
How to approach it: Assess the market (size, growth, how crowded, customer habits), the company's fit and edge versus incumbents, and the economics of a single outlet (revenue, rent, staff, breakeven). Then choose an entry route: own stores, franchise, or partnership. Recommend only if the outlet economics and a credible edge both hold.
Case 3: Market sizing
Prompt: Estimate how many electric bicycles are sold in the Netherlands in a year.
How to approach it: Start from the population, convert to households or adults, estimate what share owns an e-bike, and divide by the average years a bike is kept to get annual replacement, then add first-time buyers. State each assumption and give a range, not a single false-precise number.
Case 4: M&A
Prompt: A large supermarket group is considering acquiring a fast-growing meal-kit delivery startup. Should it?
How to approach it: Look at the target on its own (growth, profitability, why it is for sale), the strategic fit and synergies (customers, logistics, buying power, brand), and the price and risks (integration, churn, whether growth is durable). Recommend based on whether the fit and a sensible price line up, not on growth alone.
Preparation
A simple prep plan
Further resources
Where to practise and go deeper
A curated set of well-known external resources for case practice, drills and staying current on the market. These are independent third-party sites; some are paid.
FAQ
Frequently asked questions
What is a case interview?
A case interview is a business problem the interviewer asks you to work through out loud, usually in 20 to 40 minutes. You clarify the question, structure your approach, analyse data and simple maths, and end with a clear recommendation. It mirrors the kind of problem a consultant faces on a real project.
What do interviewers actually assess?
Five things: how logically you structure an ambiguous problem, how well you analyse numbers and data, how clearly you communicate, whether you show practical business judgement, and how you stay composed under pressure. A wrong final number with strong reasoning usually beats a lucky answer with weak logic.
Should I memorise frameworks?
Know the classic structures, but do not force a memorised framework onto every case. Interviewers can tell instantly. Build a tailored structure for the specific problem in front of you; the frameworks are a toolkit, not a script.
How much maths is involved?
Enough to matter. You should be comfortable with percentages, growth, breakeven, and multiplying and dividing large numbers without a calculator. Practising mental maths until it is quick and accurate removes a common source of stress.
What is a market-sizing question?
An estimation question such as 'how many X are sold in the Netherlands per year'. There is no exact answer; the interviewer wants to see you break the problem into logical parts, use sensible assumptions, and reach a defensible number.
How should I structure my answer?
Take a moment to think, then lay out a small number of clear, distinct buckets that together cover the problem. Explain your structure before diving in, work through it one branch at a time, and keep linking back to the original question.
How many rounds of case interviews are there?
Usually several across two rounds: a first round with one or two cases, and a final round of three or more with more senior interviewers. The later cases test the same skills at a higher bar, plus more fit and judgement.
How do I prepare in a few weeks?
Learn the case types, drill mental maths daily, do practice cases out loud with a partner rather than in your head, and after each one write down two things to improve. Twenty to thirty live practice cases is a realistic target before first rounds.
Related
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