- A case interview observes how you lead a problem from start to finish: structure, maths, reading charts and a clear recommendation. Knowing many frameworks is not the point, and applying one without adapting it to the problem weakens your answer.
- McKinsey, BCG and Bain have different habits (who leads the case, how fit is tested), but offices and interviewers vary a lot. Your recruiter is the best source for your own process.
- Fit and the McKinsey PEI deserve the same effort as the case. Choose your own stories early and rehearse them aloud.
- The number of cases you have done matters less than the quality of the feedback you get and how quickly you fix recurring errors.
- Start with a diagnosis of where you stand, then follow a plan by weeks. If time is short, focus on the few things interviewers notice first.
Case interview preparation is easier when you see the interview from the other side of the table. The interviewer is not checking whether you know the "right" framework. They are asking a simpler question: would I trust this person in front of a client next month? Everything in this guide is organised around that question.
If you are applying to McKinsey, the interviews usually come after the online test; the complete McKinsey Solve guide covers that step. This page covers the interviews themselves.
What a case interview tries to observe
A case is a short simulation of consulting work. You receive a business problem, often a real one simplified by the interviewer, and you have 25 to 35 minutes to understand it, organise it, analyse some data and say what the client should do. The interviewer plays the client, the manager and the source of data at the same time.
What they observe is not one skill but a sequence. Can you work out what the question really is? Can you build a plan for this specific problem? Are your numbers right, and do you say what they mean? Can you read a chart quickly? When you reach the end, do you give an answer, or a summary of what you did? And throughout, do you move the case forward yourself, or wait to be told what to do next?
Most firms condense this into a handful of dimensions. Our sample coaching report uses five, which map closely to what interviewers write down:
Structuring and prioritisation
A plan built for this problem, with a clear place to start and a reason for it.
Analytical and quantitative skills
Correct calculations, clean set-up, and charts read accurately.
Business judgement and insight
What the numbers mean for the client, and ideas that fit the situation.
Case leadership
Proposing the next step yourself, without waiting for prompts.
Communication and synthesis
Short, ordered answers, and a recommendation that starts with the answer.
How a typical interview runs
A first-round interview usually lasts about an hour and combines a fit or experience part with a case. The diagram below shows a common sequence. The order can change: some interviewers start with the case, and at Bain the behavioural part may be a separate interview.
Two moments carry more weight than candidates expect. The first is the minute after the prompt, when you decide what to ask and what to build; a weak start is hard to recover from because every later analysis depends on it. The second is the recommendation, which is the last thing the interviewer hears before writing their notes.
Why frameworks alone fall short
Standard frameworks are useful when you start, because they show you which areas a business problem can involve. The trouble begins when they replace thinking. A list of generic boxes such as "market, competitors, customers, company" could be used for almost any case, so it tells the interviewer nothing about how you understand this one. McKinsey's own interviewing page makes the same point: there is not one logical solution, and candidates should adapt their approach to the problem.
A strong structure uses the client's facts. If the client is a gym chain whose members are growing while profit falls, the structure should say where growth could hurt profit: discounts, crowding, acquisition costs. You will see exactly this in the mini-case below.
How McKinsey, BCG and Bain differ
The three firms test the same core abilities, but their habits differ. The table summarises what the firms publish and what candidates commonly report. Treat it as a starting point, because each office, role and interviewer can work differently, and processes are changing.
| Step | McKinsey | BCG | Bain |
|---|---|---|---|
| Before interviews | McKinsey Solve for most consulting roles (official) | Online case or numerical assessment, depending on office (official regional pages) | A digital assessment for consulting roles (official) |
| Case style | Often interviewer-led: you answer a series of set questions (reported) | Often candidate-led: you choose the path (reported) | Mixed; candidates report both styles and frequent market sizing |
| Fit part | Personal Experience Interview: two examples for each of four areas (official) | Free-form fit, often one experience in depth and "why BCG" (reported) | Behavioural questions; some roles have a separate interview (official) |
| Final round | Partners, more open cases, decision in a debrief (reported for all three firms) | Same | Same |
Ask your recruiter how many interviews you will have, whether the case is interviewer-led or candidate-led, how fit is tested, and whether there is a written or online part. Recruiters answer these questions routinely, and the answer for your office beats any general table, including this one. Some offices are also piloting interviews that involve AI tools, in different ways.
The practical difference is smaller than it looks. An interviewer-led case still rewards candidates who propose the next step, and a candidate-led case still expects you to answer each question precisely. Prepare for both styles, and adjust the balance once you know your process.
A mini-case from prompt to recommendation
The case below is fictional and built for this guide. It is short: a real case would have more back and forth. Read each question, try your own answer first, then compare it with the solution. At the key steps, a weaker and a stronger answer sit side by side.
Your client, Harbour Gyms, runs 20 gyms in the UK. Over the last three years its membership has grown strongly, yet its operating profit has fallen from £6m to £2m a year. The CEO asks: why has profit fallen, and what should we do about it?
Part 1: clarify the question
The question
You have the prompt. What do you ask before building anything?
Solution
Ask only what could change your plan. Three questions do most of the work here:
- Objective. What does success look like, and by when? The CEO wants profit back to around £6m within two years.
- Scope. Has the business changed shape? No: the same 20 gyms throughout, no new sites, no closures.
- Business model. How do members pay? A monthly fee, with promotional discounts for new members; there is some extra revenue from personal training.
"Can you tell me more about the gym industry in the UK, and who the main competitors are? Also, what is the company's mission?"
"Before I structure this, three quick questions. What profit level and timeline would count as success? Has the number of gyms changed over these three years? And how do members pay: a flat monthly fee, or different plans and discounts?"
The stronger version asks things that change the analysis. Knowing the gym count is unchanged tells you that growth came from existing sites, which points to crowding and pricing rather than expansion costs.
Part 2: build a structure for this problem
The question
Take a minute, then present how you would find out why profit fell.
Solution
Profit fell by £4m. Profit is revenue minus costs, so the structure splits that gap and, within each side, lists only the drivers that could plausibly move in this situation. It ends with a hypothesis and a place to start.
- Revenue: has it fallen, and why?
- Members: how many, and how many join and leave each year
- Average fee actually paid: list price, discounts, mix of plans
- Other revenue: personal training, classes, retail
- Costs: which have risen, and why?
- Fixed costs per gym: rent, staff, equipment (unchanged sites, so probably stable)
- Costs that grow with members: cleaning, maintenance, card fees
- Cost of winning members: marketing and promotions
- Market context: is this Harbour's problem or the whole market's?
- Low-cost competitors opening nearby, and their prices
- Changes in what members expect to pay
- Hypothesis and start: growth may have been bought with discounts, so revenue per member fell while costs per member rose. I would start with revenue per member.
"I would look at internal and external factors. Externally: the market, the competitors and the customers. Internally: revenue, costs and operations. Then I'd come up with recommendations."
"Profit is down £4m, so I want to know how much comes from revenue and how much from costs. On revenue: members, the fee they actually pay, and extra services. On costs: fixed costs per gym, which should be stable since the sites haven't changed; costs that grow with members; and the cost of acquiring them. I'd also check whether competitors explain it. My hypothesis is that growth came through discounts, so I'd like to start with revenue per member."
The weaker structure could fit any case, so it shows nothing about this one. The stronger one uses the facts already given (more members, same gyms), states a hypothesis and proposes where to begin, which is case leadership from minute three.
Part 3: read the exhibit
The question
The interviewer hands you Exhibit 1. "What do you take from this?"
Solution
First say what the chart shows, then check the scale, then draw the conclusion. Members grew by half, from 40,000 to 60,000. The average fee fell from £50 to £30, a drop of 40%. Since membership rose while fees fell, calculate the effect on revenue. For this simplified exercise, treat the year-end member counts as representative of each full year and assume that revenue from other services is unchanged:
2022: 40,000 members × £50 = £2.0m a month, or £24m a year
2025: 60,000 members × £30 = £1.8m a month, or £21.6m a year
Revenue change: £21.6m − £24m = −£2.4m a year
The implication: with 50% more members, Harbour earns 10% less from fees. Membership growth has been paid for with price. Revenue explains £2.4m of the £4m profit fall, so about £1.6m must come from higher costs.
"Members went up steadily every year, from 40 to 60 thousand, which is good news. The fee went down a bit. So the company is growing."
"Two lines move in opposite directions: members up 50%, average fee down 40%. Multiplying them, monthly fee revenue goes from £2.0m to £1.8m, so about £2.4m less a year. That explains a bit more than half of the £4m drop. The rest should be costs, so I'd like to look at those next."
The weaker answer describes the bars and stops. The stronger one connects the two series, does one simple calculation, ties the result to the £4m question and proposes the next step.
Read the title, the axes and the units before the data; on a two-axis chart, check which series belongs to which axis. Then describe the main movement in one sentence. Finally, say what it means for the question you are answering, and what you want to look at next.
Part 4: find the rest of the gap in costs
The question
You ask about costs. The interviewer tells you: rent and staff are unchanged. Costs that grow with members (cleaning, maintenance, card fees) are about £2.50 per member per month. Marketing spend went from £1m to £2m a year, mostly on the introductory discount campaign. Does this explain the gap?
Solution
Work out the cost of the extra members, then add the marketing increase.
Extra members: 60,000 − 40,000 = 20,000
Extra member costs: 20,000 × £2.50 = £50,000 a month, or £0.6m a year
Extra marketing: £2m − £1m = £1.0m a year
Higher costs: £0.6m + £1.0m = £1.6m a year
Together with the revenue effect, the gap closes: £6m − £2.4m − £0.6m − £1.0m = £2m, today's profit. The diagnosis is now complete. Harbour spent more to attract members who pay less, and each of them adds a running cost.
"Let me calculate... 2.50 times 60,000 is 150,000, times 12 is 1.8 million, plus 2 million marketing... that's 3.8 million, which is more than the gap. I'm not sure that works."
"Only the 20,000 extra members add cost, so 20,000 × £2.50 is £50,000 a month, about £0.6m a year. Marketing adds £1m. That's £1.6m, which is exactly the gap left after revenue. So the story holds: about 60% of the fall is lower fees, 40% the cost of growth."
The weaker answer uses total members and total marketing instead of the change, then notices the number does not fit but does not fix it. Stating what you are calculating before you calculate prevents most of these errors.
Case maths usually depends on choosing the right inputs, keeping units consistent and checking the result against the question. Practise explaining the set-up before doing the calculation.
Part 5: test one option
The question
The marketing director proposes ending the deep introductory discount. She expects to lose about 5,000 of the 60,000 members, while the average fee rises to £36. Is it worth it?
Solution
Compare monthly fee revenue before and after, then add the cost effect.
Today: 60,000 × £30 = £1.80m a month
After: 55,000 × £36 = £1.98m a month
Revenue gain: +£0.18m a month, about +£2.2m a year
Having fewer members also saves 5,000 × £2.50 × 12 = £0.15m a year in running costs, and part of the extra £1m of campaign marketing.
Yes, on these assumptions it pays: profit could rise by more than £2.3m a year before any marketing saving. The key risk is the assumption itself. If many more members leave, or competitors are cheaper, the gain shrinks. Before deciding, Harbour should test the change in a few gyms.
A good candidate also proposes other levers without being asked, grouped so the interviewer can follow: price (plans by time of day, fewer and shorter discounts), retention (keeping members who already pay full price), extra revenue (personal training, classes) and cost (acquisition spend targeted at gyms with spare capacity).
Part 6: give the recommendation
The question
"I have one minute. What should we do?"
Solution
Start with the answer, support it with two or three numbers, then give risks and next steps.
"So, we looked at revenue and costs. Members went up from 40 to 60 thousand but the fee went down. Then we looked at costs, and marketing doubled. We also looked at the discount. So overall I think there are several things the company could consider, like pricing and marketing."
"Harbour should end the deep introductory discount and stop buying growth with price. Profit fell £4m for two reasons: fee revenue fell £2.4m because the average fee dropped from £50 to £30, and the cost of growth added £1.6m, including £1m more marketing. Ending the discount would add about £2.2m a year even if we lose 5,000 members. The risk is that more members leave than expected, so I'd test it in four or five gyms over the next quarter, and in parallel look at retention and off-peak plans."
The weaker answer retells the case in order. The stronger one gives a decision in the first sentence, backs it with the numbers the CEO will remember, and closes with a risk and a concrete next step.
Notice what made the difference across the six parts. It was never knowledge of the gym industry. It was asking useful questions, building the plan from the client's facts, connecting each number to the question, and saying where to go next.
The skills behind a strong case
The mini-case shows six skills at work. You can train each one separately before you put them together in full cases.
Structuring
A structure is a plan to answer a question, not a list of topics. Build it from the client's objective, split it into parts that do not overlap and together cover the problem, and go one level deeper only where it matters. Close with a hypothesis and where you would start.
Short example. For "should a hospital buy a second MRI scanner?", a weaker opening lists "market, costs, competition". A stronger one asks whether the extra scans would pay for the scanner: demand that is lost today (waiting lists, referrals elsewhere), revenue per scan, and the full cost of the machine and its staff.
Maths
Case maths is arithmetic under mild pressure: percentages, growth, break-evens, simple multiplications with large numbers. The common errors are choosing the wrong input, losing a zero and forgetting units. Say the formula before the numbers, round sensibly and check whether the result is plausible.
Short example. "Revenue grew from £80m to £100m. What is the growth?" Saying 20% is the classic slip; the growth is £20m on a base of £80m, so 25%.
Reading charts
Interviewers often hand over a chart instead of a table to see whether you can find the point quickly. Read the title, axes and units first, find the one or two movements that matter, and say what they mean for the question. Charts with two axes, like Exhibit 1, are popular precisely because the story only appears when you combine the two series.
Communication
Lead with the conclusion, then the reasons. Number your points when there are more than two, so the interviewer can follow ("three reasons: first..."). Keep answers short and let the interviewer pull more detail if they want it.
Synthesis
At the end, and whenever you finish an analysis, summarise in terms of the question: what we now know, and what it means for the decision. A summary of what you did ("we looked at revenue, then at costs") is not a synthesis.
Leading the case
Even in an interviewer-led case, propose the next step after each analysis and explain why. "This explains about half the drop; I'd like to look at costs next" shows that you know where you are in the problem and where you are going.
Fit and the McKinsey PEI
Candidates often prepare the case for weeks and the fit part for an evening. That is a mistake, because the fit part is scored too and it is the part you can prepare most precisely. Interviewers want to understand who you are, why you want this job and how you behave in real situations.
Three kinds of questions come up almost everywhere: your background ("walk me through your CV"), your motivation ("why consulting, why this firm") and your experiences ("tell me about a time you..."). At McKinsey, the Personal Experience Interview goes deep on one story at a time; McKinsey asks candidates to prepare two examples for each of the four areas it assesses, and expects a conversation rather than a recited script. At BCG and Bain, fit questions are often broader, but follow-up questions can still go deep.
How to prepare:
- List eight to ten real situations from your studies, work and life where you led, influenced someone, overcame difficulty or achieved something hard.
- For each, write down what you personally decided and did, why, and what changed as a result. Use "I" for your own actions, not "we".
- Match stories to the areas your target firm assesses, with a backup for each, so you never have to reuse a story within the same round.
- Tell each story aloud in about two minutes, then let someone ask "why?" and "what would you do differently?" at least three times. That is where generic answers break down.
- Write your "why consulting" and "why this firm" answers with reasons that are specific to you, backed by a conversation you had or something you did.
Long context and short action. If two thirds of the story is background and the decisions you made take thirty seconds, the interviewer learns little about you. Spend most of the time on what you did and why.
How interviewers decide
Understanding how a decision is made changes how you prepare. The process below is the general practice at large consulting firms; scales, forms and the weight of each part differ by firm and are not published.
What the interviewer writes down
During the case, interviewers take notes on evidence, not impressions: the structure you proposed, whether a calculation was right the first time, how many prompts you needed, the exact words of your recommendation. After the interview, they rate each dimension on the firm's scale, write a short justification and give an overall recommendation, usually within the same day.
The justification matters because others will read it. "Needed two prompts to set up the break-even, then got it right" is a different signal from "set up the break-even unprompted and checked it against current volumes". This is why small habits, such as saying the formula first or proposing the next step, show up in decisions.
How the debrief works
After a round, interviewers discuss each candidate together. They compare notes across interviews and look for consistency: one average case among strong ones is usually discussed differently from the same weakness appearing in every interview. A clear strength helps when someone in the room is ready to argue for you; a dimension rated well below the bar is hard to offset, even with good scores elsewhere.
What counts as a red flag
- A calculation error that leads to a wrong conclusion and is never noticed or corrected.
- Answering a different question from the one asked, or never giving an answer at all.
- A structure that could fit any case and is not used afterwards.
- Needing the interviewer to tell you what to do at every step.
- Becoming defensive when challenged, instead of reconsidering.
- Fit stories that stay vague under follow-up questions, or claims on the CV that do not hold up.
Mistakes on their own are rarely decisive. Interviewers expect some, and a candidate who notices an error, says so and fixes it often leaves a better impression than one who was never tested. What hurts is an error that is not noticed, or a pattern that repeats.
How to organise your preparation
Good preparation alternates three activities: learning how cases work, drilling single skills on your own, and practising full cases with other people. The proportion changes as you progress.
Study and solo practice
Start by understanding the format: read a few complete cases with solutions, and watch or read how strong candidates handle them. Then drill skills on your own, because live partners are scarce and drills are fast. Ten minutes of mental maths a day, two structures written for unfamiliar prompts, and one chart summarised in two sentences build more skill than reading another case book.
Practice with other people
Live cases with other candidates are where you learn to think aloud, handle interruptions and manage time. They are essential, and they have a limit: another candidate sees whether you reached the answer but rarely sees why an interviewer would hesitate. They tend to miss a structure that sounds plausible but is generic, a recommendation that is really a summary, or a habit of waiting for prompts.
That is why the number of cases you have done matters less than the quality of feedback you get and the speed at which you fix recurring errors. A smaller number of cases with precise feedback and targeted drills is more useful than repeatedly making the same mistakes. After every case, write down one thing to keep and one thing to change, and check whether the same item appears again.
A plan by starting level
The table gives an eight-week plan for beginners and a four-week plan for candidates with some practice. Adapt it to your starting point, available time and interview dates, using the final column to check your progress.
| Phase | Starting from zero | Some practice already | What to check |
|---|---|---|---|
| Understand the format | Weeks 1 to 2: read cases, start daily maths | A few days: refresh the format | You can describe each phase |
| Drill single skills | Weeks 2 to 4: structures, charts, maths | Week 1: drill your weakest skill | Fewer repeated errors |
| Full live cases | Weeks 3 to 7: two to four a week, with feedback | Weeks 1 to 3: three to five a week | Recommendation in under a minute |
| Fit and PEI | From week 2: stories written, then told aloud | From week 1 | Each story survives three "why?" |
| Final polish | Week 8: cases in your target firm's style | Week 4: same | Same quality on a tired day |
If you have little time, or a final round is coming
When the interview is days away, do not try to cover everything. Focus on what interviewers notice first:
- Ask your recruiter about the format, so you practise the right style of case and fit.
- Do two or three full cases with the best partner you can find, and note your two recurring errors.
- Drill those two errors only, every day.
- Rehearse your "why consulting", "why this firm" and your strongest stories aloud.
- Practise the opening (clarifying questions and structure) and the recommendation on extra prompts; they frame everything else.
- For a final round, expect more open cases and deeper follow-up on your weakest point; prepare to discuss business judgement, not only analysis.
A scorecard to identify what to improve
It is hard to judge your own case, especially right after it. Use this scorecard after every practice case, ideally together with your partner's notes. Mark where you stand on each row, and pick the row furthest from the right-hand column as your next drill.
| Dimension | Below the bar | At the bar | Above the bar |
|---|---|---|---|
| Structuring | Generic list, not used later | Covers the problem, no overlaps | Built on the facts, with a hypothesis and a start |
| Maths | Errors not noticed | Correct, after a restart | Formula first, checked against the question |
| Charts | Describes the data | Finds the main movement | Explains the implication and the next step |
| Judgement | Ideas unrelated to the client | Sensible ideas | Prioritised ideas tied to the numbers |
| Case leadership | Waits for prompts | Proposes a step when asked | Proposes the next step after each analysis |
| Synthesis | Retells the case | Answer, then reasons | Answer, two numbers, risk, next step |
| Fit and PEI | Vague, "we" stories | Clear stories with a result | Personal decisions that survive follow-ups |
Score what happened, not what you meant. If you needed a prompt, it was a prompt, even if you would have got there. Patterns across five or six cases are more informative than any single score.
The hardest rows to score yourself are judgement, leadership and synthesis, because they depend on how an experienced interviewer perceives you. They are also the rows where outside feedback changes the most.
When coaching helps
Many candidates prepare well with partners and self-study alone. Coaching with a former interviewer is useful at three specific moments: at the start, to get a precise diagnosis and set an effective plan; when you are stuck and no longer know what to change; and before an important round, to rehearse under realistic conditions.
What changes compared with practice among candidates is the judgement behind the feedback. An experienced interviewer can tell you which errors would actually weigh in a debrief, which ones nobody would notice, and what to work on first. With 1:1 coaching with Franco, every session is a realistic interview, followed by a debrief and a written report.
This is what that report looks like. The examples below come from a sample report for a fictional candidate; the full version is available to read.
The scores matter less than the explanation beside them. In the sample, the candidate's structure was good, but the break-even calculation needed two prompts. The report names the exact slip (dividing cost by seats instead of by the fare) and shows the correct path, so the next practice can target it.
The priorities turn feedback into a plan: state the formula before the numbers, compare the result with today's figure, and propose the next step yourself. Those are the same habits that separated the weaker and stronger answers in the mini-case above.
"The way you pushed me on structuring and, especially, on communication made a huge difference in the final rounds."
P., after 7+ sessions, with McKinsey and Bain New York offers. One candidate's experience; results depend on each candidate and process.
1:1 interview coaching
Practise with a former BCG Principal and know exactly what to fix next
Franco Borgonovo spent ten years at BCG and has conducted more than 1,500 interviews, over 800 of them for MBB firms. Every session is with him, and is followed by a written report with your scores and priorities.
- Start with one session for a diagnosis and a plan
- Packages of 3, 5 or 10 sessions add a progress dashboard, practice materials and email support
- Money-back guarantee if the coaching does not meet your expectations
Not sure which option fits? The free call is for exactly that: tell Franco your target firms, dates and where you feel stuck.
Frequently asked questions
How long does case interview preparation take?
It depends on your starting point and on your interview dates. Use six to eight weeks as a planning reference if you are starting from zero, or three to four weeks if you already have some practice. Measure progress by repeated errors disappearing, not by the number of cases completed.
How many practice cases should I do?
There is no reliable number. Focus on cases followed by precise feedback and targeted drills. Track whether recurring errors disappear rather than aiming for an arbitrary case count.
Do I need business knowledge?
Not much. Interviewers expect you to understand how a business makes money (revenue, costs, customers, competitors) and to reason sensibly about the industry in the case. Specialist knowledge is rarely required, and when it is, the interviewer gives you the facts.
Can I use a calculator or prepared notes?
Usually not. In most case interviews you work with pen and paper, and online or AI-assisted formats have their own rules. Check the instructions for your interview, and ask your recruiter if they are unclear.
Are case interviews different for experienced hires?
The format is similar, but the bar on judgement is higher. Interviewers expect you to bring business sense from your own field, lead the case with less help and tell fit stories with real responsibility and impact.
What should I do if I make a mistake during the case?
Say so as soon as you notice, correct it and state what changes in the conclusion. Interviewers expect some mistakes; an error you catch and fix calmly is very different from one that silently drives a wrong answer.
Final checklist
Your next step
Pick your starting row in the plan, run one full case this week and score it honestly with the scorecard. If you want an experienced interviewer's view of where you stand and what to fix first, a single session gives you a diagnosis and a written plan to follow on your own.
Coaching with Franco
Get a precise diagnosis before your next round
A realistic interview, a debrief and a written report with your priorities. Start with one session, or talk it through for free first.
About Franco
Franco Borgonovo
Former BCG Principal · 10-year tenure · Official BCG coachFranco spent ten years at BCG, from intern to Principal, interviewing and selecting candidates as a global lead recruiter. He is still an official BCG coach for new hires, and today works one to one with candidates on applications, McKinsey Solve and interviews.
More about Franco →- BCG: Associate recruitment in the United States, United Kingdom, Australia and New Zealand · official office-specific online case and numerical assessment process
- McKinsey: Interviewing (careers page) · Problem Solving Interview and Personal Experience Interview; read 2 November 2026
- Bain & Company: Interviewing (careers page) · interview types by role, digital assessment for consulting roles; read 2 November 2026