Author: Taylor Warfield, Former Bain Manager and interviewer

Last Updated: April 30, 2026

 

Brainstorming in case interviews is a structured exercise where you generate and organize ideas to solve a specific business problem. Unlike the opening framework question, brainstorming questions usually appear mid-case and test whether you can think broadly, creatively, and in a MECE (Mutually Exclusive, Collectively Exhaustive) way under time pressure.

 

According to data from McKinsey, BCG, and Bain, brainstorming questions appear in roughly 70% of all case interviews. In my experience coaching over 5,000 candidates, brainstorming is one of the top three areas where candidates lose points, alongside structuring and math. The good news is that brainstorming is also one of the easiest skills to improve with the right approach and practice.

 

But first, a quick heads up:

 

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What Is Brainstorming in a Case Interview?

 

Brainstorming in a case interview is a question type where the interviewer asks you to generate a list of ideas, reasons, or solutions related to a specific business problem. Your job is to come up with as many relevant ideas as possible and organize them into a clear, logical structure.

 

Brainstorming questions typically sound like: "What are all the ways our client could increase revenue?" or "What factors might explain why our client's costs have risen 20% in the past year?" You are expected to take a moment to organize your thinking, then walk the interviewer through your ideas in a structured, top-down manner.

 

Brainstorming is common across all types of case interviews, from profitability cases to market entry to operations. Whether you are interviewing at McKinsey, BCG, Bain, Deloitte, or any other consulting firm, you will almost certainly face at least one brainstorming question per case.

 

How Is Brainstorming Different from Building a Framework?

 

The biggest difference is timing and scope. A case interview framework is your opening structure that lays out the major areas you need to investigate to solve the entire case. It is broad and strategic. Brainstorming questions come later in the case and are narrower. They ask you to generate specific ideas within a focused topic area.

 

For example, your framework might include "revenue growth" as one of four major buckets. A brainstorming question might then ask: "What specific strategies could our client use to grow revenue by 15% in the next two years?" The framework identifies the area. Brainstorming fills it with concrete ideas.

 

Both skills require MECE thinking, but brainstorming demands more creativity and depth. According to former McKinsey interviewers, candidates who can generate 8 to 12 structured ideas on a brainstorming question consistently score in the top 20% of all candidates.

 

When Do Brainstorming Questions Come Up During a Case?

 

Brainstorming questions most often appear in the middle of a case, after you have set up your framework and started investigating. The interviewer might ask you to brainstorm after you have analyzed some data or identified a key issue.

 

There are two common types of brainstorming questions. Investigative brainstorming asks you to explore causes or drivers: "What could explain why our client is losing market share?" Prescriptive brainstorming asks you to recommend actions: "What could our client do to improve customer retention?"

 

In McKinsey-style interviewer-led cases, the interviewer will directly prompt you with a brainstorming question. In candidate-led cases at firms like BCG and Bain, you may need to initiate brainstorming yourself as part of your analysis. Either way, you need to be ready to generate ideas on command.

 

What Are the Most Common Types of Brainstorming Questions?

 

Brainstorming questions in case interviews fall into seven main categories. Knowing these categories in advance lets you recognize the question type instantly and structure your answer faster. Based on analysis of hundreds of real case interviews across MBB firms, these are the most common brainstorming prompts you will encounter.

 

Question Type	What It Asks You to Do	Example Question
Revenue Growth	Generate ideas for increasing top-line revenue	"What are all the ways our airline client could grow revenue?"
Cost Reduction	Identify ways to lower costs or improve efficiency	"How could our manufacturing client reduce production costs by 10%?"
Root Cause Analysis	List potential reasons behind a problem or trend	"What factors could explain why our client's customer satisfaction scores dropped?"
New Product or Service Ideas	Brainstorm product concepts or extensions	"What new products could a snack company launch to reach health-conscious consumers?"
Risk Identification	Identify risks, threats, or challenges to a plan	"What risks should our client consider before acquiring this competitor?"
Customer Retention	Suggest strategies to reduce churn or increase loyalty	"What could a subscription software company do to reduce its 25% annual churn rate?"
Market Entry Strategies	Propose specific approaches to entering a new market	"How could our client enter the Southeast Asian market for electric vehicles?"

 

For a deeper look at how each of these question types fits into different case types, see our complete guide to case interview types.

 

What Does a Great Brainstorming Answer Look Like?

 

A great brainstorming answer is broad, deep, MECE, and insightful. It covers the problem from multiple angles, goes at least two levels deep under each angle, avoids overlaps, and includes at least one or two ideas that the interviewer would not expect. In my experience interviewing candidates at Bain, the best answers typically included 8 to 12 specific ideas organized under 3 to 4 top-level categories.

 

What Are the Four Qualities of a Strong Brainstorming Answer?

 

• Broad: Your answer covers the problem from multiple distinct angles, not just one or two. If the question is about revenue growth, you should cover pricing, volume, new products, new markets, and more.

 

• Deep: Each top-level category has 2 to 3 specific, concrete ideas underneath it. "Improve marketing" is not deep enough. "Run targeted digital ads to the 25 to 34 age group based on browsing behavior" is deep.

 

• MECE: Your categories do not overlap with each other, and together they cover all the important ground. MECE thinking is the gold standard for structured problem solving in consulting. For more on this principle, see our case interview frameworks guide.

 

• Insightful: Beyond the obvious ideas that any candidate would list, you include one or two creative, unexpected suggestions that show genuine business judgment. These are the ideas that make an interviewer write "strong" on the scorecard.

 

What Does a Bad Brainstorming Answer Look Like?

 

The most common mistake is blurting out a random list of ideas with no structure. A candidate who says "We could do more marketing, maybe lower prices, try social media, expand to new cities, improve the product..." has listed five ideas but demonstrated zero structured thinking. The interviewer cannot follow the logic because there is none.

 

The table below compares a weak answer and a strong answer to the same brainstorming question: "What are all the ways our restaurant client could increase revenue?"

 

Weak Answer (Unstructured)	Strong Answer (Structured)
"We could do more marketing, add new menu items, raise prices, offer delivery, do catering, improve the ambiance, partner with food bloggers, get on Uber Eats, open more locations."	"I see three main levers for revenue growth:   1. Increase visits per customer: loyalty program, targeted promotions, seasonal events   2. Increase spend per visit: upsell combos, premium menu tier, beverage pairings   3. Reach new customers: delivery via third-party apps, catering for corporate events, social media partnerships with local food influencers"
9 ideas, no structure, no prioritization, no depth	9 ideas, 3 clear categories, specific and actionable, easy for the interviewer to follow

 

Both answers contain roughly the same number of ideas. But the strong answer demonstrates structured thinking, business judgment, and clarity. That is what separates a "pass" from a "strong pass" in consulting interviews.

 

What Is the Best Step-by-Step Approach to Brainstorming?

 

Follow this four-step approach every time you get a brainstorming question. It works for every question type, in both interviewer-led and candidate-led cases. Having coached thousands of candidates, I can tell you that candidates who follow a consistent process outperform those who wing it every single time.

 

Step 1: Clarify the Question

 

Before you start brainstorming, make sure you understand exactly what the interviewer is asking. If the question is vague, paraphrase it back and ask for confirmation. This takes 10 to 15 seconds and prevents you from going down the wrong path.

 

For example, if the interviewer says "How can we improve this business?", you should clarify: "Just to confirm, are we looking specifically at ways to improve profitability, or growth more broadly?" According to Bain's interviewer training materials, candidates who clarify the question before brainstorming score higher on average because their answers are more focused and relevant.

 

Step 2: Take 60 to 90 Seconds to Structure Your Ideas

 

Ask the interviewer for a moment to organize your thoughts. In McKinsey interviews, you typically get around 2 minutes. In BCG and Bain candidate-led cases, 60 to 90 seconds is standard. This is your most important investment of time.

 

During this silent thinking time, your goal is to create 3 to 4 MECE categories (your top-level buckets) and list 2 to 3 specific ideas under each one. Write shorthand notes on your paper. Use abbreviations to save time. For instance, "Rev" for revenue, "Cust" for customer, "Mkt" for market.

 

Here is how to divide your thinking time effectively:

 

Time	Activity	Goal
First 15 seconds	Identify your top-level categories	Decide on 3 to 4 MECE buckets that cover the problem
Next 30 to 45 seconds	Fill in specific ideas	List 2 to 3 concrete ideas under each bucket
Final 15 seconds	Review and add creative ideas	Check for gaps and add 1 to 2 unexpected, creative ideas

 

If you want a step-by-step system for building these structures quickly, my case interview course walks you through proven techniques with 20 practice cases you can work through in as little as 7 days.

 

Step 3: Present Your Ideas Top-Down

 

Once your thinking time is up, present your answer using the Pyramid Principle: start with the big picture, then go deeper. Begin by telling the interviewer how many categories you have, then walk through each one with its supporting ideas.

 

A strong opening sounds like: "I have identified three main areas where our client could reduce costs. First, supply chain optimization. Second, labor efficiency. Third, overhead reduction. Let me walk through each one." Then dive into the specific ideas under each category, numbering them as you go.

 

This top-down approach is the same communication method used by consultants at McKinsey, BCG, and Bain when presenting findings to clients. According to a survey of over 200 former consulting interviewers, structured communication during brainstorming is the single most common differentiator between candidates who pass and those who do not.

 

Step 4: Prioritize and Connect Back to the Case

 

After presenting all of your ideas, do not just stop. Tell the interviewer which ideas you would prioritize and why. This shows business judgment, which is one of the key skills every consulting firm evaluates.

 

For example: "Based on what we know about the client's situation, I would prioritize supply chain optimization first because it has the highest potential impact and can be implemented within 6 months. I would explore labor efficiency second." Then connect your brainstorming back to the broader case by suggesting what data or analysis you would want to do next.

 

What Techniques Help You Generate More Ideas?

 

Even with a structured approach, many candidates struggle to fill their categories with enough specific ideas. Here are four proven techniques that will help you generate more ideas faster. In my coaching experience, candidates who practice these techniques for just one week typically double the number of ideas they can produce in a 90-second brainstorming window.

 

Top-Down Brainstorming

 

Start with your major categories first, then work downward into specific ideas. This is the most natural approach for candidates with strong structuring skills. You decide on your 3 to 4 buckets, then ask yourself: "What specific actions or factors fall under this bucket?"

 

Top-down brainstorming works best when you can immediately identify clear, MECE categories. For example, if asked about revenue growth, you might quickly land on: increase price, increase volume, and launch new products. Then you fill in concrete ideas under each one.

 

Bottom-Up Brainstorming

 

Start by listing every idea that comes to mind, then group them into categories afterward. This approach works well when the topic is unfamiliar or when you are having trouble finding clean categories.

 

Write down 6 to 8 ideas quickly, then look for patterns. You will usually notice that your ideas cluster into 3 to 4 natural groups. Label those groups, and you have your structure. This approach is slower than top-down, so use it as a backup when you cannot immediately see the right categories.

 

The Inversion Technique

 

Instead of asking "How can we solve this problem?", ask "What would make this problem worse?" Then flip each answer into a positive action. This technique is surprisingly effective because it helps you identify ideas you would never think of directly.

 

For example, if the question is "How can our client improve customer satisfaction?", invert it: "What would make customers unhappy?" Answers might include long wait times, rude staff, poor product quality, and confusing billing. Now flip each one into an improvement: reduce wait times, train staff on service, improve quality controls, simplify billing. You just generated four concrete ideas in seconds.

 

The Analogy Technique

 

Think about how a similar problem was solved in a different industry. This is one of the most powerful creativity tools in consulting. According to Harvard Business Review research, cross-industry analogies generate solutions that are rated 30% more creative than within-industry ideas.

 

If your client is a hotel chain trying to increase customer loyalty, think about what airlines do (frequent flyer programs), what coffee shops do (punch cards), or what software companies do (subscription models with increasing benefits). Pulling ideas from other industries shows the interviewer that you can think beyond the obvious.

 

How Do You Handle Brainstorming in McKinsey vs. BCG and Bain Interviews?

 

The core brainstorming skills are identical, but the format changes how you use them. Understanding these differences gives you a real edge. Based on interview data from recent MBB recruiting cycles, here is how brainstorming plays out differently depending on the firm.

 

Factor	McKinsey (Interviewer-Led)	BCG and Bain (Candidate-Led)
When brainstorming happens	The interviewer directly asks a brainstorming question at a specific point in the case	You may need to initiate brainstorming yourself when you identify a need for it
Time to think	Typically about 2 minutes of silence to structure your answer	About 60 to 90 seconds is standard before you start presenting
Depth expected	McKinsey values broad, deep structures with 3 levels of detail	BCG and Bain prioritize focused, actionable ideas with clear prioritization
Follow-up pressure	Expect "What else?" or "Can you think of anything else in that category?"	Less direct prompting, but you should proactively offer additional ideas
How to stand out	Show exhaustive coverage and creative depth within each category	Show strong prioritization and tie ideas directly to case data you have already seen

 

For a full breakdown of how McKinsey interviews differ from BCG and Bain, read our McKinsey-style case interview guide.

 

How Should You Communicate Your Brainstorming Answer?

 

A great brainstorming answer delivered poorly is still a mediocre answer. Communication quality accounts for roughly 30% of the overall evaluation in consulting case interviews, according to feedback from former MBB interviewers. Here is how to present your brainstorming effectively.

 

How Do You Use the Pyramid Principle for Brainstorming?

 

The Pyramid Principle, developed at McKinsey, says you should always present information from the top down: start with the conclusion or summary, then provide supporting details. For brainstorming, this means:

 

• State the number of categories: "I have identified four main areas."

 

• Name all categories first: "These are: pricing changes, operational efficiency, product expansion, and customer acquisition."

 

• Dive into each one: Walk through the specific ideas under the first category, then move to the second, and so on.

 

• Number your ideas: "Under pricing, I see three options. First... Second... Third..." This makes it easy for the interviewer to follow and refer back to specific ideas.

 

This approach mirrors how consultants present findings in real client meetings. Practicing it during brainstorming will help you build a skill that matters far beyond the interview.

 

How Do You Handle "What Else?" Follow-Up Questions?

 

"What else?" is one of the most common follow-ups in case interviews. The interviewer is testing two things: how deep your thinking goes and how well you perform under pressure. Based on data from McKinsey's interview process, interviewers are trained to push candidates with "What else?" at least two to three times during brainstorming.

 

When you hear "What else?", do not panic. Use these three strategies:

 

• Go deeper in an existing category: Take one of your top-level buckets and add another layer of specificity. If you said "improve marketing," now add "specifically, run A/B tests on email subject lines to increase open rates by 15%."

 

• Use inversion: Quickly flip the problem to find ideas you missed. Ask yourself what would make the situation worse, then reverse it.

 

• Borrow from another industry: Think about how a completely different company or industry solves a similar problem. This often surfaces creative ideas that impress the interviewer.

 

If you truly cannot think of anything else, it is okay to say: "Those are the main ideas I have. Is there a specific area you would like me to explore further?" This is better than guessing or repeating ideas you already shared.

 

What Are the Biggest Brainstorming Mistakes to Avoid?

 

In my experience coaching over 5,000 candidates, these are the mistakes that come up again and again. Avoiding them will immediately put you ahead of most candidates. According to feedback from consulting interviewers, the first two mistakes on this list are the most common reasons candidates fail brainstorming questions.

 

Common Mistake	Why It Hurts You
Listing ideas with no structure	The interviewer sees unorganized thinking, which signals you would struggle on real consulting projects where structured communication is essential
Staying too surface-level	Saying "improve marketing" without specifying how shows you cannot move from strategy to execution. Interviewers want to see concrete, actionable ideas.
Not asking for thinking time	Jumping straight into brainstorming without pausing leads to disorganized answers. Every interviewer expects you to take 60 to 90 seconds to think.
Overlapping categories	Having a "marketing" bucket and a "customer acquisition" bucket creates overlap. This violates the MECE principle and suggests sloppy logic.
Ignoring the case context	Generic ideas that could apply to any company show you are not connecting your brainstorming to the specific facts of the case
Not prioritizing	Treating all ideas as equally important misses the chance to show business judgment. Always tell the interviewer which ideas you think matter most and why.
Giving up after "What else?"	Saying "That is all I have" too early signals limited thinking depth. Use inversion or cross-industry analogies to push yourself further.

 

How Do You Practice Brainstorming for Case Interviews?

 

Brainstorming is a skill you can improve rapidly with focused practice. Candidates who spend just 15 minutes a day on brainstorming drills for two weeks typically see significant improvement. Here is how to practice effectively, whether you are preparing solo or with a partner.

 

What Are the Best Solo Practice Drills?

 

• Timed brainstorming sprints: Pick a brainstorming prompt from the table earlier in this article. Set a timer for 90 seconds. Write down as many structured ideas as you can. Review your answer for MECE coverage, depth, and creativity. Then do another one. Aim for 5 to 10 prompts per session.

 

• Industry immersion: Read one business news article per day. After reading, brainstorm 3 to 4 ways the company in the article could solve the problem described. This builds your business intuition and makes brainstorming feel more natural.

 

• Build a brainstorming idea bank: Keep a running list of ideas organized by topic: customer retention strategies, cost reduction tactics, revenue growth ideas, and so on. Over time, you will build a mental library you can draw from instantly during interviews.

 

• Practice the communication: Recording yourself presenting a brainstorming answer out loud is one of the most effective solo drills. Listen to the recording and check whether your answer flows logically from top-level to detail.

 

How Should You Practice with a Partner?

 

Partner practice is the fastest way to improve because you get real-time feedback. According to data from successful MBB applicants, candidates who practiced 30 to 50 cases with a partner passed at 3x the rate of those who prepared solo. Even if you cannot do full cases, isolated brainstorming drills with a partner are extremely valuable.

 

Have your partner give you a brainstorming prompt, then present your answer as if it were a real interview. Ask them to push back with "What else?" at least twice. After each drill, get specific feedback: Was your structure clear? Were your ideas specific enough? Did you prioritize? Were any ideas surprising or creative?

 

If you want expert feedback on your brainstorming skills, interview coaching provides 1-on-1 sessions where you can practice brainstorming and other case skills with personalized guidance.

 

Brainstorming Case Interview Example (Worked Through)

 

Let's walk through a complete brainstorming example so you can see the four-step approach in action. This example is based on a real case I have used in interviews.

 

Prompt: "Our client is a national gym chain that has seen a 15% decline in membership renewals over the past 18 months. What are all the potential reasons for this decline?"

 

Step 1 (Clarify): "Just to confirm, we are looking at reasons for the decline in renewals specifically, not new sign-ups? And this is across all locations nationally, not just specific regions?"

 

Step 2 (Structure): You take 90 seconds to think and organize your ideas on paper.

 

Step 3 (Present top-down): "I see four main categories of reasons the client may be losing renewals."

 

• Category 1: Competition. New competitors may have entered the market with lower prices, better facilities, or more convenient locations. Boutique fitness studios like cycling and yoga studios have been growing at roughly 15% annually according to IBIS World data, which could be pulling members away.

 

• Category 2: Service or facility quality. Equipment may be outdated or frequently broken. Cleanliness or maintenance standards may have slipped. Staff quality or friendliness may have declined. Class schedules may not match what members want.

 

• Category 3: Pricing and value perception. Membership fees may have increased without a corresponding increase in value. Competitors may be offering similar facilities at 20 to 30% lower prices. Free or low-cost alternatives like outdoor fitness groups and home workout apps have grown significantly since 2020.

 

• Category 4: External factors. Economic slowdown may be causing consumers to cut discretionary spending. Remote work trends may have changed where people live and commute, making current gym locations less convenient. Demographic shifts in the client's core market could also be a factor.

 

Step 4 (Prioritize): "Given the 18-month timeframe, I would prioritize investigating competition first, since the timing aligns with the rapid growth of boutique fitness studios. I would also want to look at any recent price increases to see if there is a correlation with the decline in renewals. As a next step, I would ask if we have any exit survey data from members who chose not to renew."

 

This answer demonstrates all four qualities: it is broad (4 categories), deep (multiple specific ideas per category), MECE (the categories do not overlap), and insightful (the boutique fitness trend and exit survey suggestion show business awareness). For more examples of how cases are solved step by step, check out our complete case interview guide.

 

Frequently Asked Questions

 

How many ideas should you give in a brainstorming question?

 

Aim for 8 to 12 specific ideas organized under 3 to 4 top-level categories. Based on scoring rubrics from major consulting firms, fewer than 5 ideas is considered weak, while 8 or more ideas with clear structure is rated strong. Quality matters more than quantity, so make sure each idea is specific and relevant to the case context.

 

How long should you take to brainstorm?

 

Take 60 to 90 seconds of silent thinking time in most cases. McKinsey interviews typically allow up to 2 minutes. Taking less than 30 seconds usually results in shallow, disorganized answers. Taking more than 2 minutes can signal that you struggle to think quickly under pressure. The sweet spot is about 90 seconds for most candidates.

 

Can you ask for time to think during a brainstorming question?

 

Yes, and you should. Simply say: "Can I take a moment to organize my thoughts?" Every consulting interviewer expects this request and will say yes. Not asking for thinking time is actually a negative signal because it suggests you do not value structure. The only exception is if the interviewer specifically tells you to brainstorm on the fly, which is rare.

 

What if you run out of ideas during brainstorming?

 

Use the inversion technique or the analogy technique to generate additional ideas. Flip the problem upside down or think about how a different industry solves it. If you are truly stuck, ask the interviewer: "Is there a specific area you would like me to explore further?" This is better than repeating ideas or sitting in silence. For a full toolkit of case interview strategies, see our case interview cheat sheet.

 

Do you need industry knowledge to brainstorm well?

 

No. Industry knowledge helps you add creative, specific ideas, but the core skill is structured thinking. A candidate with no healthcare experience can still brainstorm effectively about hospital efficiency if they use a strong structure and logical reasoning. That said, reading business news regularly will naturally build the kind of industry intuition that makes your brainstorming answers stronger over time.

 

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