Case Interview Frameworks 2026: A Complete Prep Guide

What a case interview framework is

A framework is a list of headings plus the order in which you open them. It earns its place when the headings between them account for the whole of the client's problem and each heading can be answered with a number, a fact, or a question to the interviewer.

Firms use the word themselves. Oliver Wyman asks candidates on its published water park case to "use creative problem-solving to develop a logical framework to estimate daily revenue", checked 30 September 2026 at oliverwyman.com. Deloitte publishes a five-step approach to apply during a case: "Understand the issue", "Identify the underlying assumptions", "Summarize specific issues and findings", "State your recommendations", "Outline next steps and expected results/impacts", checked 30 September 2026 at deloitte.com.

Two consequences come out of how firms write it. The first is that headings are scored on what they produce. Charles River Associates tells candidates to "be prepared to explain how you came to your answer and show your math", checked 30 September 2026 at crai.com. A heading that yields no number and no question produces nothing to show.

The second is that these seven frameworks overlap. Cost appears in the profit identity, in the supplier force, in the capacity decision and in the entry decision. The overlap is why three or four of them held well enough to be rebuilt from scratch beat a memorized library of fifteen. Issue trees covers the general case, where no named framework fits the prompt.

The seven frameworks, and what each one outputs

Each row names the categories, the output, and the prompt that calls it. The order runs from the identity every other framework lands on to the decisions that are built on top of it.

Three of the seven end on a single number, which makes them the fastest to defend: profitability, capacity change and market entry. Two end on a range: mergers and acquisitions, and the 4Ps, where a price band holds until the client picks a point in it. Two end on a judgment supported by facts: the business situation and the five forces.

Profitability, solved from one identity

The profitability framework splits profit into price, volume, variable cost and fixed cost, then asks which of the four moved. It is the framework every other one on this page eventually lands on, because a recommendation that changes nothing in those four terms changes nothing in the client's results.

Here is the whole chain on a worked case. A chain runs 34 gyms and is losing money. Average membership per site is 1,420. The monthly fee is 46 dollars. Variable cost per member is 9 dollars a month. Fixed cost per site is 58,000 dollars a month.

Contribution per member is 46 minus 9, so 37 dollars. Across the site, 1,420 times 37 is 52,540 dollars a month. Against 58,000 dollars of fixed cost that is a loss of 5,460 dollars a month. Over twelve months, 5,460 times 12 is 65,520 dollars per site, and 65,520 times 34 is 2,227,680 dollars a year.

Now solve it backwards, twice, because the identity has two levers.

1. Members. Fixed cost divided by contribution per member is 58,000 divided by 37, which is 1,567.6 rounded, so 1,568 members. The gap from 1,420 is 148 members per site, and 148 divided by 1,420 is 10.4 percent.
2. Price. Contribution per member has to reach 58,000 divided by 1,420, which is 40.85 dollars rounded. Adding back the 9 dollars of variable cost gives a fee of 49.85, so 3.85 dollars more, and 3.85 divided by 46 is 8.4 percent.

A 10.4 percent membership gain and an 8.4 percent price rise are different projects with different odds, and the conversation moves to which one the market allows. The profitability framework runs a second case end to end, exhibit included.

The business situation framework, three Cs and product

The business situation framework opens four headings: customer, company, competition and product. It answers the diagnostic prompt, where results moved and the cause is unknown, and its output is a shortlist of causes ranked by what each one would be worth.

Oliver Wyman's published dairy farm case shows the competition heading doing real work. A private equity client picks between two farms in one Illinois county. Farm one has 10,000 cows at 100 units of milk each. Farm two has 5,000 cows at 80 units each. The state sets the standard milk price at 20 dollars a unit and organic at 30. Feed costs 10 dollars a unit at farm one and 15 at farm two. Fixed costs are 5 million and 3 million dollars. Checked 30 September 2026 at oliverwyman.com.

Farm one: 10,000 times 100 is 1,000,000 units, times 20 dollars is 20 million of revenue, minus 10 million of feed and 5 million of fixed cost, so 5 million of profit at a 25 percent margin. Farm two: 5,000 times 80 is 400,000 units, times 30 dollars is 12 million, minus 6 million of feed and 3 million of fixed cost, so 3 million at a 25 percent margin. Identical margins from different structures.

The firm's published conclusion reads "Farm one has more than 70% of the market share in terms of the number of cows and milk production volume." On volume, 1,000,000 of 1,400,000 is 71.4 percent. On cows, 10,000 of 15,000 is 66.7 percent. One threshold, two bases, two answers, so the base belongs in the sentence. The 3Cs framework handles the version without product, and the 4Cs handles the version where cost gets its own heading.

The 4Ps, each one carrying a number

The 4Ps framework opens product, price, place and promotion. It answers the launch prompt and the pricing prompt, and its output is a commercial plan in which at least the price heading carries a figure.

Oliver Wyman's published pricing case prices a digital autism therapy before launch in India. Specialist doctors charge about 300,000 INR a year, the product "can reduce the need for in-person therapy by one-third", annual fixed costs run about 10 billion INR, and the firm's own answer sizes the reachable base at roughly 1 million users. Checked 30 September 2026 at oliverwyman.com.

Price gets three readings from those lines. Value: 300,000 divided by 3 is 100,000 INR, which the firm calls "the upper limit". Cost: 10 billion divided by 1 million is 10,000 INR per user, and at the published 50 percent markup, 10,000 times 1.5 is 15,000 INR. Competition: the firm lists rival products at 50,000, 60,000 and 75,000 INR. The published recommendation is "a subscription-based model priced between INR 15,000 and INR 30,000 annually".

Two of the four headings carry nothing in that case. Place and promotion are absent from the prompt, and writing them down anyway buys silence where a number should be. Bain's published fashion case has the same shape from the other side: both options it asks you to compare move price and promotion, and product and place are not variables of the case. The 4Ps framework prices each of the four on one launch.

Porter's five forces as a split of value

The five forces are threat of entry, supplier power, buyer power, substitutes and rivalry. The institution that hosts the author defines the model as "a framework for understanding the competitive forces at work in an industry, and which drive the way economic value is divided among industry actors", checked 30 September 2026 at isc.hbs.edu.

That definition is what makes the model calculable. Value divided among actors adds up to the end price, so each force is a claim on a share of it. The same page states the mechanisms: "The threat of entry, therefore, puts a cap on the profit potential of an industry", powerful suppliers "charge higher prices or demand more favorable terms", powerful customers "force prices down or demand more service at existing prices", a substitute "meets the same underlying need that the industry's product meets in a different way", and intense rivalry "drives down prices or dissipates profits by raising the cost of competing".

The dairy case above prices two of the five. Buyer power is at its limit, because the state sets the standard price at 20 dollars a unit and the farm has no pricing move at all. Supplier power is the live force: feed costs 10 dollars a unit at one farm and 15 at the other, and a 5 dollar move across 1,000,000 units is 5 million dollars, which is the whole of farm one's profit. The margin of that business sits entirely in a supplier negotiation.

The same page warns that "Industry structure changes over time, and is not static", which is the limit of a five-force sketch written in ninety seconds. Porter's five forces works a full split of a hundred dollars of end price.

Mergers and acquisitions, and the return equation

A merger and acquisition framework opens standalone value, synergies, price, risk and exit. Its output is a maximum price plus the share of promised synergies that has to be delivered for that price to hold, which is a different question from whether the target is a good business.

The dairy case is a private equity diligence with the price left out. Both farms clear their breakeven twice over: farm one needs 5 million divided by 10 dollars of unit contribution, so 500,000 units against 1,000,000 produced, and farm two needs 3 million divided by 15, so 200,000 units against 400,000. Neither number appears in the firm's published answer, and both come from lines it publishes. No asking price, no multiple and no holding period are given, so the candidate introduces them and states them out loud.

The published structure is worth copying for its third branch. The firm's three branches are farm profitability, local dairy market dynamics, and compatibility with the client's own firm and portfolio. Most candidate structures on an acquisition prompt stop at the asset, and the third branch is where the buyer's existing expertise, risk tolerance and portfolio fit get a heading.

The firm also prints its evaluation criteria under each question, and the criterion under the opening question is the "Ability to identify the key question and pertinent information". That is scored before any structure appears, which rules out a grid recalled in the first ten seconds. M&A cases work a deal where 85.4 percent of the savings have to land, and commercial due diligence separates bought growth from earned growth.

Capacity change, read line by line

A capacity change framework opens volume gained, the cost lines that scale with it, the marginal margin on the extra volume, and the risks outside the arithmetic. Its output is one annual profit swing, and the published example below produces a swing small enough to change the recommendation.

A US grocery distributor decides whether to move its leased fleet from 53-foot to 58-foot trailers. Longer trailers carry 10 percent more volume on the same number of trips. Fuel runs 700,000 dollars a year and rises 8 percent. Loaders run 500,000 and rise 10 percent with volume. Drivers run 900,000 and do not move, because the number of trips is unchanged. Extra leasing is 80,000, extra maintenance 15,000, and insurance of 60,000 rises 5 percent. The trucks deliver 8,000,000 dollars of revenue-generating product a year at a 30 percent marginal margin. Checked 30 September 2026 at oliverwyman.com.

Costs first: 700,000 times 8 percent is 56,000; 500,000 times 10 percent is 50,000; 80,000 plus 15,000 is 95,000; 60,000 times 5 percent is 3,000. Then 56,000 plus 50,000 plus 95,000 plus 3,000 is 204,000 dollars. Benefit next: 8,000,000 times 10 percent is 800,000 dollars of revenue, and 800,000 times 30 percent is 240,000 dollars of margin. Finally 240,000 minus 204,000 is 36,000 dollars a year.

The firm's own conclusion is that Urban Grocers "should probably not take this route given the risks and costs that were not yet studied", and it names the risk that decides: grocery margins are thin, shelf space and warehouse space are unchanged, so the extra product spoils before it sells. Operations cases cover the version where the constraint is a station on a line.

Market entry against three breakeven bars

A market entry framework opens market size, breakeven volume, the route in, and the economics after entry. Its output is a yes or no against a bar, and three firms publish three different bars for the same kind of question.

Bain's published coffee shop case charges the full opening cost against the first year: 3 pounds a cup, 1 pound of variable cost, 163,740 pounds to run the shop for a year, 245,610 pounds to open it. Unit contribution is 2 pounds, 163,740 plus 245,610 is 409,350, and 409,350 divided by 2 is 204,675 cups. The firm's answer calls that achievable at about 3 percent of a 7,000,000 cup market, and adds that "A better answer would take into account how long it would take for her to recoup the cost to open the store". Checked 29 September 2026 at bain.com.

McKinsey's published drinks launch leaves capital out of the bar. Fixed costs are "$40 million in total", each bottle costs 1.90 dollars to produce and deliver, and the price to retailers is 2 dollars. Unit contribution is 0.10 dollars, and 40 million divided by 0.10 is 400 million bottles. Checked 29 September 2026 at mckinsey.com.

Oliver Wyman's water distribution case refuses a profitable business on time. Volume is 250,000 kL a day over 300 days, so 75 million kL; at 10 rupees that is 750 million of revenue; variable cost of 5 rupees is 375 million, plus 200 million of fixed cost gives 575 million; so 175 million rupees of profit before tax. The published conclusion is that entry "does not align with the client's investment criteria for a five-year payback period". Ask which bar applies before computing one. The market entry framework runs the full comparison.

Where firms disagree about frameworks

Firms publish opposite instructions on framework use, and a candidate who carries one firm's rule into another firm's room is following the wrong one. Three disagreements are on the record.

Kearney, under the tip it calls thinking top down, writes: "Try to avoid forcing your solution to fit a standard framework. The only things it needs to fit are the problem, the business, and the objectives", checked 30 September 2026 at kearney.com. Simon-Kucher's Frankfurt junior recruiting lead writes the other way: "A solid understanding of economic principles and frameworks can also be beneficial, especially in our core focus areas such as pricing, marketing, digitalization, and sales", checked 30 September 2026 at simon-kucher.com. One sentence governs what you do with a live problem. The other governs what you understand before you walk in.

L.E.K. publishes seven numbered steps that pull against each other. Step three, "Stick to your approach", reads "Outline how you are thinking and move methodically to address each issue, point-by-point". Step six, "Come up with an answer", reads "Commit yourself to a course of action, but show flexibility and a willingness to rethink in the face of new data", checked 30 September 2026 at lek.com. The firm publishes both instructions and no signal for switching between them.

Deloitte and Kearney disagree on vocabulary. Deloitte's own LeadAuto answer key names MECE and places a MECE internal and external split in the upper tier of its two tiers, "In addition to the above, a great answer may also include", checked 30 September 2026 at usrecruiting.deloitte.com. Kearney names no framework anywhere on its page. MECE covers the property itself, and when to use a framework sets out the switching signal.

Choosing a case interview framework in five steps

The selection rule is five reads of the prompt, in order, and it takes under a minute. It satisfies both published positions above, because knowing a category's economics is preparation and imposing a category grid on a live problem is process.

1. Read the prompt for a quantity. A requested number means writing the identity for that number first: profit, revenue, capacity, breakeven. Nothing else outranks this.
2. Read it for a decision with a price. Buy, enter, expand and launch each have their own framework above, and each ends on a bar. Ask what the bar is before computing against it.
3. Read it for a diagnosis. A result that moved for unknown reasons calls the business situation headings, and the first branch to open is the one worth the most if it is the cause.
4. Read it for scope. When none of the above fits, decompose from the client's decision and say out loud which branch you will open first and why. First principles structuring works a parking garage this way, restating it in space-hours before any heading exists.
5. Run the named frameworks over your structure at the end. The five forces and the 4Ps work as a checklist for the heading you forgot, after your own structure exists.

Bain describes what the five steps are serving. It writes that it is "not looking for a single right answer" and that it watches "how you think, structure problems, and build on ideas as the conversation evolves", checked 29 September 2026 at bain.com. A structure that evolves is one whose branches were chosen after the prompt was read.

Where a borrowed structure loses points

The weights below are ours, read from the rubric code our own grader runs. No consulting firm publishes a marking scheme, so none of what follows is any firm's view.