Case interview overview: everything you need to know
A deep dive on the interview format popularized by McKinsey, BCG and Bain
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Case interview fundamentals | Four core skills | How to prepare
In this deep dive, we're going to give you a crash course of the vaunted case interview. If you're already deep into your interview prep process, we recommend you check out our more advanced posts on things like the future of the consulting industry and the importance of being authentic in case interviews. However, if you're just ramping up or looking for a primer on the case interview, you're in the right spot. Let's jump in!
A case interview is an interview type which focuses on a challenging and relevant business scenario that the candidate must navigate through. In this post, we'll get you up to speed on case interviews by covering the fundamentals, four core skills and how to prepare.
Part I: The fundamental facts about case interviews
We're going to start by setting the fundamental context on case interviews. Understanding who uses case interviews, what exactly the format of a case interview looks like and why they've become so popular will give you important context.
Which companies use case interviews?
Initially, companies like McKinsey & Co., The Boston Consulting Group and Bain & Co. popularized the use of case interiews. This helped these firms find and attract the best talent and there techniques caught on and spread like wildfire. Today, every single consulting firm, from Deloitte, Accenture, Strategy& to smaller firms like LEK, OC&C use case interviews.
The spread of case interviews to new companies
Given the success that firms like McKinsey, BCG and Bain have had with case interviews, other world class firms are starting to use case interviews as well. Specifically, the big tech firms that have achieved mega-scale in the last few decades, Amazon, Google, Facebook, Microsoft, Salesforce, et al, are using case interviews for their product management, product marketing management and strategy roles. While these companies don't use case interviews exclusively, the case interview is quickly becoming the dominant interview type for business roles (eg non engineering roles).
The anatomy of a case interview
While every case interview is a different - one might be about a medical device firm entering the Chinese market for the first time versus an entertainment company looking to price movies for digital platforms - the key components of a case interview are remarkably consistent from topic to topic and firm to firm. That's good news because it means you can anchor yourself on the key traits of the case interview and it will help navigate through any case you end up facing.
| Phase | Length | Key components |
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| Case introduction & structuring | ~5 minutes |
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| Problem analysis & discussion | ~20 minutes |
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| Conclusion & next steps | ~5 minutes |
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The game is changing: new ways to prepare for case interviews
In the past decades, it used to be that candidates could successfully prepare for case interviews through a combination of natural talent plus preparation that included things like:
- Reading a book about case interviews
- Watching a video about cases
- Memorizing some canned frameworks (eg Porter's 5 forces)
But, those tactics don't cut it today. In 2017, it's estimated that 700,000+ people applied to the top consulting firms and firms like McKinsey, BCG and Bain will hire on the order of 1% of them. To land an offer, you need to do more.
The best candidates focus on skill building
Today, the best candidates are actively preparing for case interviews by building the core skills that are tested. Candidates do this through a mix of:
- Interactive drills (eg, RocketBlocks charts drills)
- Targeted skill building (eg, practicing case starts)
- Mock interviews (eg, 1-on-1 mock interview with a coach)
In Part III, we'll go into detailed recommendations for how to best prepare for cases. For now, set aside the question of how to build the necessary skills and let's first make sure your understanding of what core skills are needed and why is solid.
Part II: The four core skills tested in case interviews
While case interviews are intimidating and very widely in the content they cover, everything from a healthcare pricing case to a Chinese market entry for an entertainment firm, they do consistently test the same set of core skills. This is great! It means that despite the incredible variety, someone who has mastered the core skills will be well suited to solve any case thrown at him/her.
To understand exactly how these skills are tested, we're going to use a sample case prompt:
"Ok, your client is a quick service restaurant, traditionally called "fast food" in the US, that serves sub style sandwiches across 2,000+ US locations. It's considering moving into the breakfast market for the first time and they've engaged us to help analyze the opportunity and make a recommendation."
Case Skill #1: Problem structuring
Problem structuring is the art of taking a massive, nebulous problem and breaking it down into a core set of components which can then be logically and methodically covered by a consulting case team. Often, you'll hear consultants talk about formulating a MECE framework, which stands for a problem structure that is collectively exhaustive and mutually exclusive. What does that mean? Essentially, it means that 1) the framework covers all the critical potential issues that could influence the answer and 2) that each component is independent and can be analyzed separately. For now, you don't need to go into all the details of MECE, but when you're ready for it, you can check out our MECE deep dive here.
Why is problem structuring so critical to consultants?
Problem structuring is used daily by consultants to break down client problems into manageable work streams the case team can attack. At every level of the firm, this skill is employed from Partner's breaking up an entire case into large work streams for their Principals and Managers to junior Associates structuring their approach to sizing markets, surveying the competitive landscape, etc.
| Don't | Do |
| List everything and try to "boil the ocean" | Structure your thoughts into independent "buckets" |
| use a canned framework like Porter's 5 forces | Propose a specific framework that addresses the case head on |
| Try to keep everything in your head | Draw your framework as a reference for yourself and the interviewer |
A bad response to structuring the quick service restaurant case would be unfocused, list a ton of different items to look into and potentially suggest something like using Porter's 5 forces to solve the case. Let's take a look at what a good example might look like:
A good answer
To analyze this case, I'd like to look at three key issues. First, I want to look at the overall breakfast market. It will be important to understand how big that market is, what it's growth profile looks like over the next decade and the competitive landscape. Second, I want to analyze the operational impact. Since we're looking at an entirely new meal offering they'll be lots of operational considerations such as equipment, staff training, hours of operation, and more. Finally, I want to put it all together with a financial analysis of the revenue opportunity, costs and initial investment.
Case Skill #2: mental math
Your mental math and quantitative skills will get tested throughout the case with estimates, market sizings, growth forecasts and all sorts of quantitative drills. This isn't surprising either, especially once you think about the fact that consultants do hundreds of these types of calculations daily.
Why does mental math matter so much in a world where everyone uses excel?
Yes, as a consultant you'll have access to Excel and calculators but that isn't the point. The ability to quickly sanity check numbers, estimate quantitative impact and prove or disprove hypotheses with a little "back of the envelope" math enables consultants to work at speedy clip.
| Don't | Do |
| Calculate everything in your head | Show your work, which can help you catch errors |
| Needlessly use specific, difficult to compute numbers | Round messy numbers to simplify calculations |
| Calculate silently | Voice over your calculations so the interviewer can follow along |
Returning to our quick service restaurant example, let's consider how a candidate might answer the question: how much do you expect the company to make in annual profit if the they have 2,100 US locations, the average price of a breakfast will be $5 and they think that, on average, each location will serve 50 breakfasts per day at a 20% margin?
A mediocre candidate would try to keep all the math straight in his/her head, calculate the answer silently and provide it to the interviewer without showing any work. If he/she gets the right answer, this might be fine. But a far superior approach would be to show the work, provide a voice a over and walk through the calculations methodically.
A good answer
"OK, so if we're looking to calculate annual profit, I'm first going to calculate annual revenue and then apply the 20% margin to reach the profit estimate. I'm going to begin with the number of locations, and if it's OK I'll use 2,000 to keep the math a little simpler. So 2,000 locations multiplied by 50 breakfasts per location, means we can expect to serve 100,000 breakfasts daily. At an average price of $5, we can then expect $500,000 in daily revenue. To scale to a year, I'm going to round 365 days to 400 and thus we can expect $200M in annual revenue. Finally, we know margin is 20% so therefore they can expect just below $40M in annual profit."
Case Skill #3: charts and data analysis
The life of a consultant is filled with data and charts. As a result, the case interview process is no different so analyzing complicated sets of data and pulling insights out of charts is a skill you'll want to demonstrate great aptitude in. Whether it's merrimekko market share charts, harvey ball comparisons or a three dimensionsal bubble chart like below, you'll face more than a few of these throughout your interviewing process.
Why are charts the "lingua franca" of consulting?
Providing data driven insights is a core part of the consultant's role and since displaying reams of data is an inefficient, not to mention boring, way to communicate insights to top executives, charts are the solution. Thus, consulting mid-project read outs and final presentations are often chock full of informative cases and data displays that back up and highlight the key findings from the case.
| Don't | Do |
| Start speaking without interpreting the data | Take a momment and orient yourself to the data |
| Repeat every data point shown to the interviewer | Focus on the key trends and insights the data points to |
| View the data in a vacuum from the rest of the case | Look for and call out second level insights |
Again let's return our sample case on the quick service restaurant. A mediocre candidate will look at the chart above and make two main mistakes. First, he/she will tend to repeat too much data from the chart, rather than focusing on the key insights. Second, he/she will view the data in isolation and forget to connect it back to the case at hand.
A good answer
"Interesting. What I'm seeing here is that we've got an analysis of our competitors and along the x-axis we can see the number of US locations and on the y-axis we see the number of breakfast items on the menu. Furthermore, the size of the bubble is the margin they've earned. Looking at the data, it seems that their isn't a strong correlation between number of locations and margin but it does appear that fewer items on the menu might lead to a higher margin. Specifically, it looks like there is a breaking point at above 8 menu items. Finally, it's worth further exploration to see why fewer menu items is correlated with higher margin - it's possible that it's operational simplicity and savings or maybe an easier marketing message to succeed with or it could be both. Either way, there will be an interesting insight there for our client."
Case Skill #4: communication
This is one of those case skills that candidates tend to overlook. After all, consultants are known for analytical chops and data driven insights so it seems like communication might not be that important, if you've got the right answer and the data to back it up. That couldn't be more wrong.
If consulting is so quantitative, why does communication matter?
Consultants don't just need the analytical chops to get the right answer, they also need the ability to communicate it clearly and create alignment with clients.
Essentially, the job of consulting is a two step process if abstract away all the other detail:
- Find the right answer
- Sell the right answer
It is the 2nd part where effective communication becomes a "deal breaker" skill. One of the most common reasons why exceptionally talented analytical people fail in consulting case interviews is because they can not effectively communicate why their ideas and answers are valuable. Simply being right isn't enough. Your audience needs to understand and agree that you're right - that takes great communication skills!
| Don't | Do |
| Ramble on | Structure your communication clearly |
| Use unsubstatiated arguments | Back up key points with data |
| Repeat yourself needlessly | Be concise |
Returning to our quick service restaurant example one final time, let's think about how a great candidate would communicate when handling the conclusion of this case. The key things to remember are that while a mediocre candidate will ramble, repeat him/herself and use unsubstantiated arguments, a good candidate will communicate in a structured, logical flow.
A good answer
"After everything we've analyzed, my recommendation is that the client pursue the breakfast opportunity in the US for three key reasons. First, the market size is large and competition is fragmented so breaking in seems feasible. Second, the operational hurdles, while important, all appear to be solvable and the company has a track record of handling these type of updates successfully. Finally, the financial opportunity checks out. We estimated the company can make $40M in annual profit and that clears their investment hurdle criteria. Thus, I'd recommend they move forward with this opportunity."
Finally, for a live discussion on communication, see Genelle Kahan, a former Bain & Co. Manager who spent 9 years with the firm, discuss the three key traits of great case interview communication.
Part III: How to prepare for your case interviews
OK, we've now covered the case basics in Part I and the core skills you need in Part II, now it's time for the fun part: preparing for your case interviews. The good news is that like any life skill, case interviewing is something that you can improve dramatically with practice. But that last part is key: it does take dedicated, targeted practice on building the core skills to succeed.
It's not easy, but the great news is that case interviews skills are highly valuable both in the interview and the on the job. So your time will be well spent whether you end up working as a consultant or in any role - you won't regret be sharp in mental math, data analysis, communication or problem strucuturing no matter what career you choose!
đź’ˇ Shameless plug: Our consulting interview prep can help build your skills
The "Athlete" model of preparation
Quite simply, the best way to practice is learn by doing. Consider your favorite athlete, maybe it's Golden State Warrior Steph Curry or the reigning tennis champion of the world, Serena Williams, and how they got so good at their sport.
Steph Curry didn't become the world's best 3 point shooter by reading a book about 3-pointers. And Serena Williams didn't come to dominate the global tennis circuit by wathcing a few videos about how to serve, backhand and volley. These athletes learned to dominate their respective sports by practicing the core skills needed day in, day out.
Success in business and interviewing is no different. Your case interviews are a game of sorts. Thus, the best way to excel in them is to work on your core case skills the same way an athlete might build their core skills.
The Skill Building loop for case interviews
Many candidates start preparing for case interviews by simply going through the motions. For example, they might immediately jump into doing mock interviews with friends. For most people, this is a sub-optimal way to start.
Instead, we recommend kicking things off by doing an honest self-assessment of how you perform in the core skill areas. This process helps establish a baseline and then lets you know where you need to improve the most. With that knowledge, you can start practicing and honing your skills. Essentially, this starts a skill building loop that looks like what we've outlined in the table below:
| Steps | Example | How RocketBlocks can help |
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| Assess your skills | My mental math skills, particularly long division, need some work since I haven't done that since high school! |
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| Build your skills | I really need to get better at structuring the initial case problems, which I find tough since I've never had to do that under such time pressure |
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| Test your skills | Do a mock interview with a peer or an 
experienced interviewer |
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| Repeat until ready | I'm getting better at chart analysis but need to practice maybe 15 - 20 more to really hit the next level |
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Conclusion
Finally, as you think about case interviews, remember that they are simply a conversation about a challenging business problem. At the end of the day, the interviewer is simply trying to assess whether you're capable of and interested in, dissecting business problems and recommending solutions to clients. Ultimately, you should try to have fun with the process and enjoy yourself.
Further reading:
- The three questions an interviewer is asking him/herself about you in an interview
- What does the career path of a consultant look like?
- Deep dive: what do the next five years look like for McKinsey, BCG and Bain
P.S. Are you preparing for consulting interviews?
Real interview drills. Sample answers from ex-McKinsey, BCG and Bain consultants. Plus technique overviews and premium 1-on-1 Expert coaching.
