Case Interview Prep Guide: The Confirmed Window Is 16 Days

Whether you need case interview prep, by country and role

Before building a plan, check the plan is needed. One firm's graduate process does not contain a case interview.

Deloitte's UK early careers page at deloitte.com publishes four stages plus the outcome: Apply Online, Immersive Online Assessment, Job Simulation, Final Stage Assessment, Outcome. It states: "Regardless of whether you're applying for a Summer Vacation Scheme, Industrial Placement, or one of our full-time Graduate or Brightstart programmes, our assessment process follows the same structure". The word case appears in none of the four.

What that process does require is different work entirely. The final stage has a discussion of about 30 to 40 minutes on a topic prepared in advance, plus a skills and motivation interview of about 50 minutes, and the preparation is compulsory: "Before you attend, we need you to complete some mandatory preparation which involves researching and conducting analysis on a topic." The same page publishes academic requirements: a 2:1 or better for graduate and work experience programmes, and 104 UCAS points across the three best A-Levels for BrightStart. The spellings of programmes and A-Levels are the firm's own.

Meanwhile the same firm publishes ten practice cases for US recruiting. Same employer, two countries, two exercises.

Three checks, in order, before you spend forty hours.

1. Read the invitation. Every firm in our corpus defers to it. McKinsey states that the recruiter confirms the interview details in advance.
2. Read the country page for the office you applied to. Not the global careers page, which generalizes.
3. Read the posting itself. Accenture's company-wide process page never mentions a case interview, and one of its own postings names case interviews twice.

Bain draws the line by role rather than geography, stating that case interviews are used for consulting roles only.

Sixteen days covers half the 43 cases five firms publish

Here is the calendar, from a Copenhagen posting read through Accenture's own Workday system at accenture.wd103.myworkdayjobs.com.

Recomputed by hand on 30 September 2026. From 18 October to 10 November is 13 days remaining in October plus 10 in November, so 23 days. From 18 October to 26 November is 13 plus 26, so 39 days. From 10 November to 26 November is 16 days.

Now put those against the work available. Firms publish 43 readable practice cases: Accenture 21, Deloitte 10, Oliver Wyman 6, McKinsey 4, Bain 2. At 45 minutes each that is 43 times 0.75, which is 32.25 hours.

• The confirmed window of 16 days, at an hour a day, gives 16 hours. That is 16 over 32.25, which is 49.6 percent of the published material.
• The full window of 39 days, at an hour a day, gives 39 hours, which covers all of it with slack.

So the decision is clear and it is the opposite of what most candidates do. Serious preparation starts when you apply rather than when you are invited, because the invited window buys you half the material. The posting says the same thing in its own words: "We therefore encourage you to familiarize yourself with consulting case interviews ahead of the bootcamp."

Deloitte publishes windows rather than dates, which point the same way: an initial interview "usually within one to two weeks" of selection, then "Expect two to three rounds of interviews", then an offer "in writing within one week of your final interview."

Two models of case interview prep, and where AI is allowed

Two firms publish preparation advice and the two models barely overlap.

L.E.K.'s page at lek.com gives four suggestions: attend campus case preparation workshops, read the business press regularly, practice with people who currently work in strategy consulting and understand the firm's type of work, and "Review the case studies and other content available throughout our website". Not one of the four names a timed exercise. It is a model of exposure.

Simon-Kucher's page at simon-kucher.com gives four of its own: discuss cases out loud, simulate interview conditions including time awareness, reflect on your approach and iterate, and build business acumen through the business press and the firm's publications. Two of those four are about deliberate practice, and one names the clock.

Both models are published by firms that hire. Our reading, and we label it as ours: the exposure model builds the vocabulary and the practice model builds the execution, and a candidate who does only the first meets a timer for the first time on the day.

McKinsey adds a boundary that matters for how you rehearse. Its interviewing page permits using AI to polish a resume, practice questions and explain a concept, and prohibits generating answers in real time during an interview or using AI during an assessment without explicit permission. So rehearsal assistance is explicitly allowed by one firm, and live assistance is explicitly not.

Forty hours of case interview prep, block by block

Forty hours is a realistic total for someone working or studying full time, spread over six weeks. Here is an allocation, and the allocation logic is ours.

Eighteen plus nine plus six plus four plus three is 40, checked by addition.

The structure share is 45 percent of the total, which is 18 over 40. That number is taken from our own structuring rubric, where Coverage carries 45 of 100. It is our weight rather than any firm's, and the allocation follows from it directly: the largest scored line gets the largest block.

Read that against what firms publish and it holds up. Every one of the four published in-case sequences opens on comprehension and structure, and none opens on arithmetic. Deloitte's five steps put "Understand the issue" first. L.E.K.'s seven put Take your time first. Accenture's six put Listen to case first. Oliver Wyman's six put pinpoint the issue first.

The fit block looks small at three hours, and it is enough for the published requirement. McKinsey asks for "two personal examples that demonstrate how you've made an impact in each of the four areas below", which is eight stories. Three hours writes eight stories and says each one out loud twice.

The arithmetic and exhibit blocks are the two that reward raw repetition most, and a subscription aimed at exactly those exists. Our RocketBlocks review reads its published prices and quotes the help center entry where it explains why it drills components and leaves whole cases to people.

What to do in the first six hours

Order matters more than volume at the start, because the wrong first move wastes the next ten hours.

1. Read four firms' published instruction sets. L.E.K.'s seven steps, Deloitte's five, Oliver Wyman's six, Accenture's six. Ninety minutes, and they disagree in four places you should notice.
2. Read one worked case as a reader. One of McKinsey's four, which the firm says contain "logic, thought processes, and suggested answers". Thirty minutes.
3. Do one case badly, out loud, timed at 30 minutes. The published lower bound for a case portion. Doing it badly is the point.
4. Write your first opening and time it. Restate, assumptions, structure, justification. Ninety seconds, twenty attempts. That is ninety minutes and it is the single highest-return block in the forty.
5. Write the eight fit stories as titles only. Thirty minutes, so the bank exists before you need it.

Six hours, and at the end of them you can open a case competently. That is a better state than having read twenty cases silently.

What to do in the last six hours

The last six hours before an interview should contain no new material.

1. Four cases in one sitting. Two firms publish four-case rounds, so this is the realistic load, and you will find out what case four feels like.
2. Twenty calculation chains, timed at three minutes each. One hour, and it resets your error rate.
3. Say your close ten times. Call, two figures, risk with direction, next step with timeframe. Deloitte's fifth published step is the one most closes omit.
4. Reread the four contradictions and pick your side. Questions against crutch, framework against no framework, hold against adapt, coachable against firm. Decide in advance rather than under time.
5. Check the mechanics. One firm's remote instruction is to disable previously installed AI note-taking software, which is the item nobody remembers.
6. Copy the equations out by hand. Profit, contribution, breakeven, margin, markup, compound growth, payback. Copying is the last rehearsal.

Nothing in that list is new learning, which is deliberate. The last six hours are for retrieval speed.

The weights that decide the allocation

The four numbers below are ours, read from the grading code in src/lib/grading. No consulting firm publishes a marking scheme, which is why an allocation has to be justified rather than asserted.

What this guide will not tell you

Four things, and each is an absence in the public record rather than something we are withholding.

How many rounds you will have. Published in three places only: Deloitte says two to three, Oliver Wyman's Brazil and Mexico page says two rounds of two, BCG Switzerland says one plus three. McKinsey, Bain, Kearney, L.E.K. and Simon-Kucher publish nothing.

How long your interview will be. Two published clocks exist, one from a 2018 document and one from a single country page.

What score you need. Nobody publishes a threshold, a weight or an aggregation rule. Bain refers to "an objective scoring system" and describes none of it.

Whether more cases beats fewer. We have not measured it, and no firm publishes anything on it. What is measurable is the material: 43 published cases, 32.25 hours to work them once.

For the day-of version of this plan, see the case interview checklist. For the cases to work, see case interview examples. For MBB specifics, see MBB case interview prep.