How to Crack a Profitability Case (Step by Step)

A profitability case asks why a company's profit is falling, or how to grow it. You crack it with one equation and four moves: write Profit = Revenue minus Cost, split each side into its drivers, drill down to find which single driver moved, and quantify the fix. The trap candidates fall into is jumping to solutions before they have isolated the driver. Do not do that. Find the broken number first, then fix it.

I conducted over 100 interviews at McKinsey, and the profitability case is the one I saw most. It is also the one most candidates think they have mastered and most candidates fumble. They know the equation. What they cannot do under pressure is decompose it cleanly, ask for the right numbers, and isolate the one driver that explains the problem. That is the whole game, and this article walks you through it with real numbers.

The profitability equation is your entire framework

Forget memorized frameworks for a moment. The most powerful structure in consulting is an equation you learned in school: Profit = Revenue minus Cost. What I liked most when I evaluated frameworks was when a candidate built from an equation instead of reciting a list. An equation is mutually exclusive and collectively exhaustive by construction. It cannot leave gaps, and it cannot double-count.

From the top equation you expand both branches. Revenue = Sales Volume times Average Selling Price. Cost = Fixed Cost plus Variable Cost, where Variable Cost = Cost per Unit times Sales Volume. That is the skeleton of every profitability case. Once you have it on paper, you have a map of every place a problem could be hiding.

Here is the full tree, written out as plain branches:

If you want the deeper logic behind why an equation beats a memorized template, I unpack it in my guide on how to structure a case interview. Structure is not memorization. It is starting from something you know and building toward something you do not.

Step 1: Confirm the goal and the type of profit

Before you decompose anything, pin down what "profit" means in this case. In roughly 80 percent of cases, the relevant measure is plain accounting profit, which is Revenue minus Cost. You do not need anything fancier unless the case demands it. If the client is weighing a one-time investment like a new machine or a new factory, you may need a break-even period (Cost of Investment divided by Annual Increase in Profit) or a return on investment (Net Profit divided by Cost of Investment). Ask. Do not assume.

Then confirm the actual objective. "Profit is down 20 percent, and the CEO wants to know why and how to reverse it" is a different case from "profit is flat, and they want to double it in three years." Your clarifying questions should all serve that goal, which I call the North Star. Any question that does not help you answer the North Star is curiosity, not strategy, and it costs you time.

Step 2: Split revenue versus cost to find the side that moved

This is the move that separates strong candidates from the rest. Do not start guessing at causes. Ask which side of the equation changed. The single most useful question in a profitability case is: has revenue fallen, have costs risen, or both?

Suppose the interviewer tells you revenue is roughly flat year over year, but total cost is up 15 percent. You have just eliminated half the tree in one question. You do not need to talk about pricing or volume at all. The problem lives on the cost side, and you say so out loud: "Since revenue is stable and costs have risen 15 percent, I'd like to focus on the cost structure and come back to revenue only if the cost side doesn't explain the gap." That sentence is what an interviewer is listening for.

If instead both sides moved, prioritize. Quantify which one moved more in dollar terms, and attack the larger one first. Always reason in dollars, not percentages alone, because a 30 percent jump in a tiny cost line matters far less than a 5 percent slip in your largest revenue stream.

Step 3: Drill down to isolate the single driver

Now you go one layer deeper on the side that moved. Costs are up 15 percent: is that fixed cost or variable cost? Fixed costs like rent and salaries do not scale with volume, so a fixed-cost spike usually points to something structural, a new lease, a hiring wave, a depreciation charge. Variable costs scale with each unit, so a variable-cost spike points to inputs, raw materials, shipping, or a supplier price increase.

Keep asking "which part of this number changed" until you hit a single line item you can name. That line item is the driver. A profitability case is not solved when you have a nice framework. It is solved when you can point at one number and say "this is the thing that broke." Everything before that is setup. Everything after is the recommendation.

A clean drill-down sounds like this. Costs up 15 percent. Of that, fixed costs are flat and variable costs are up. Within variable costs, raw materials are the same per unit, but freight cost per unit has roughly doubled. The driver is freight. Now you have something a recommendation can act on.

The drill-down works exactly the same way on the revenue side. If revenue is the side that fell, ask whether volume dropped or price dropped, because the fixes are completely different. A volume problem might be lost customers, fewer purchases per customer, or a shrinking market, and the response is demand-side: marketing, retention, new segments. A price problem might be heavier discounting, a worse product mix, or competitive price pressure, and the response is pricing strategy. One more split that earns points: separate whether the issue is the whole market shrinking, which hits everyone, or your client losing share, which is a company-specific problem. Ask whether competitors are seeing the same trend. If the whole industry is down, you have a market story; if only your client is down, you have a competitive story, and they call for different recommendations.

A worked example with real numbers

Let me run a full case the way I would want to see it in the room.

Our client is a regional coffee roaster. Last year they made 2 million dollars in profit. This year profit is 1.2 million, a drop of 800 thousand dollars, about 40 percent. They want to know why and how to get back.

Start with the equation. I ask for revenue and cost both years. Revenue held steady at 10 million dollars. Cost rose from 8 million to 8.8 million, an increase of 800 thousand dollars. Notice that the entire profit drop is explained by the cost side. Revenue is a dead end here, so I set it aside and say so.

Now I split cost. Fixed costs (rent, salaried staff, equipment) went from 3 million to 3 million, unchanged. Variable costs went from 5 million to 5.8 million. The whole increase is variable. So I drill into variable cost. They sold the same volume both years, 2 million pounds of coffee. So variable cost per pound went from 2.50 dollars to 2.90 dollars, up 40 cents per pound.

What is in that 40 cents? I ask for the variable cost breakdown. Green coffee beans were 1.80 dollars per pound last year and 2.20 dollars this year, up 40 cents. Packaging and labor per pound were unchanged. The entire driver is the price of green beans, which rose because of a poor harvest in their main sourcing region.

Now the math closes perfectly: 40 cents per pound times 2 million pounds equals 800 thousand dollars, which is exactly the profit drop. I have isolated the driver and proven it accounts for 100 percent of the problem. If you want more practice running the arithmetic cleanly under time pressure, my case interview math guide drills exactly this kind of layered calculation.

The recommendation follows from the driver. Bean prices, not the client's own operations, caused the problem. So the fix is on sourcing and pricing: hedge or lock in bean contracts to stop the bleeding, diversify sourcing regions to reduce harvest risk, and pass through part of the increase by raising the average selling price, since a 40 cent per pound cost rise on a product they likely sell for far more than 5 dollars a pound is recoverable. I would also flag the risk that competitors face the same bean prices, so a modest price increase is unlikely to lose much share.

How to communicate the answer

When you deliver the recommendation, lead with the answer. Do not narrate your journey. The first words out of your mouth are "Our recommendation is to lock in bean supply contracts and raise prices modestly, because a 40 cent per pound increase in green coffee accounts for the entire 800 thousand dollar profit drop." Then give your two or three reasons, then name the risks. Then stop talking. Executives want the conclusion first and the discipline to know when you are done.

The bottom line

A profitability case is solved with one equation and one habit. Write Profit = Revenue minus Cost, split each side, and drill until you can point at a single line item that explains the gap in dollars. Isolate the driver before you propose anything. The candidates who pass are not the ones with the fanciest framework. They are the ones who find the broken number fast and quantify the fix.

If you want to see this method run end to end alongside other case types, work through my case interview examples, each one fully worked with the back-and-forth and the math.

Go deeper

The profitability case is the backbone of the CaseMap business-concept system inside Cut to the Case, where I teach the full issue tree, the pricing and cost levers, and how to run the Interview Dance from opening to recommendation.

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