Ultimate Case Interview Guide: Preparation, Strategies & Examples

Consulting firms use a unique type of interview as part of their recruitment process. It’s called a case interview and it tests how well you can solve real-world business problems.

These case interviews are the most important part of the consulting recruitment process. However, most candidates do not know how to prepare and ace their case interviews.

In this article, I’ll teach you everything that you need to know to “ace the case” and get your dream job in consulting.

What is a case interview?

A case interview is a type of job interview where the candidate is given a real-world business problem to solve. Case interviews are used by consulting firms, such as McKinsey, BCG, and Bain.

Case interviews reflect the type of business problems that candidates will come across as a management consultant. They test the candidate’s ability to break down the problem, identify the root cause, and identify the optimal solution for the business.

Consulting firms use case interviews because they test the core skills required of a consultant. Firms are on the lookout for:

• How well you structure a complex and ambiguous business problem
• How accurately you determine which issues are important in the problem
• How comfortable you are with data (numerical and otherwise)
• How accurately you draw conclusions and recommend actions to solve the problem
• How clearly you articulate your thoughts during an interactive problem-solving discussion

Types of case interview questions

Case interview questions come in many varieties but there are a number of common business topics you should prepare for:

• Growth: The business wants to increase market share in an existing market.
• M&A: The business is considering merging or acquiring another company, such as a competitor.
• Market entry: The business wants to enter a new geography or launch a new product (see our guide to the Market Entry Framework).
• Profitability: The business wants to increase profitability or revenue, or reduce costs (see our guide to the Profitability Framework).
• General business situation: Generic case questions that don’t fit neatly into a category above (see our guide to the Business Situation Framework).

Styles of case interviews

There are two main styles of case interviews:

• Interviewer-led (high guidance, high pressure): The interviewer dictates the setting and pace of the interview. They will lead you down a path to a solution but, at the same time, will grill you with deep questions about the case. The challenge with this style is that you must quickly and confidently answer the interviewer’s questions.
• Candidate-led (low guidance, low pressure): The interview leaves the problem open to you. You need to determine the best line of questioning to find the solution. The challenge with this style is that you must independently navigate an ambiguous business problem.

How to prepare for a case interview

Learn common case interview frameworks

A case interview framework is a template that can be applied to break down and solve case study questions. It aids candidates by giving them a clear approach to resolving the case question they are given.

There are frameworks for all common case interview questions, such as market entry, profitability, and generic business situation questions.

However, you must remember that you will be penalized for applying a generic framework to your case interview question. You should treat the framework as a starting point and tailor it to the specific details of the business problem that you’re given.

Practice case interview questions

The best way to get good at case interviews is to practice case interviews (surprise!).

Top candidates will literally practice upwards of 50 or 100 case questions before their interview. There are two ways to practice case interviews:

1. Practice alone: It’s good to practice alone when you’re getting started. To do this, you’ll need to find example case questions that are structured in a question-and-answer format (e.g. these McKinsey case interview questions). This format is great because it doesn’t require an interviewer to guide you through the case.
2. Practice with a partner: After a while, you’ll need a partner to practice more complex and ambiguous cases. Look for a partner who is familiar with case interviews, as they’ll have a good understanding of how and when to provide guidance.

It can sometimes be difficult to find a good case interview partner. If you’re at university, you should start by asking peers in your classes if they’re applying for consulting firms and practicing with them. Otherwise, you could try to find a partner on the PrepLounge candidate listing or the My Consulting Coach candidate listing.

Take case preparation courses or coaching

Many candidates choose to purchase case preparation courses (like Crafting Cases, My Consulting Coach or Hacking the Case Interview) or work with coaches (like Management Consulted and PrepLounge).

I haven’t personally tried any courses or coaches. However, based on the content on their website, I really like the way that Crafting Cases teaches case interviews.

Instead of giving you generic frameworks to memorize and apply, they teach you how to create bespoke frameworks in real time during the interview. This is undoubtedly the best way to ace your case interview, so you might want to check them out.

Improve your mental math

Doing math in the privacy of your own home is one thing. It’s another thing to do math aloud and under the critical gaze of an interviewer.

You should actively practice doing mental math aloud and under time pressure.

Here are a couple of things that you should be confident with:

• Zeroes: It’s always the zeros! You need to be confident when calculating orders of magnitude (e.g. 12,000 x 120,000).
• Fractions: It helps to be familiar with translating common fractions to decimals (e.g. 1/6 = 0.16). You should know how to do this for fractions between 1/2 and 1/15.
• Common values: It also helps to know the value of common variables, such as the population of your country and the world. The trick here is to round them to the nearest number that you can confidently use with mental math (e.g. rounding the population of the world from 7.8bn to 8bn).

What to expect on the day

Case interviews follow the same format, no matter which consulting firm you’re applying for.

There are three stages to a case interview:

1. Fit interview (15-30 mins): The interviewer will ask questions about your suitability and motivation to be a consultant at the particular firm that you’re applying for (e.g. the dreaded “why consulting” question).
2. The case interview question (30-45 mins): The interviewer will give you a real-world business problem to solve (more details below).
3. Open questions (5-10 mins): At the end of the interview, you’ll have an opportunity to ask questions to the interview.

To be successful, you’ll need to do well during all three stages. However, the most important stage is the case interview question.

How to answer a case interview question

Answering a case interview question requires a balance between structure and flexibility.

On the one hand, it’s extremely useful to have a pre-planned response structure so that you’re not starting from scratch in a high-pressure interview. On the other hand, you need to adapt the structure to the specific nuances of the case question.

Here is what I’ve found to be the most useful way to answer a case interview question:

Step 1. Listen and clarify

The interviewer will present you with the case interview question. Start by noting down the question, restating the question to confirm you understood it correctly, and then clarifying the objective of the question.

Step 2. Take time to prepare an approach / framework

You should immediately ask your interviewer if you can take a couple of minutes to think through the question and structure your thoughts. They’ll always give you this time.

Use this time to identify the type of case interview question that you have been asked, as it’s not always obvious (e.g. profitability, market-entry, etc.). Once you’ve done this, then figure out the most appropriate framework to apply.

But you cannot simply apply a generic framework to your question. In fact, interviewers will penalize candidates who apply a generic framework in a case interview.

Interviewers are looking for your ability to break down the specific business situation they’ve given you, so you need to adjust your framework to apply to your question.

Your framework should cover all your hypotheses for the root cause of the business problem. For example, if you have a profitability case, then you need to consider both revenues and costs.

Step 3. Confirm the objective and share your approach

Once you have prepared your framework, you should share it with your interviewer.

Start by re-iterating the objective of the case question, then spin your paper around and walk through your approach step-by-step.

Why do you do this? In the case interview, you should consider your interviewer as your client. You want their buy-in on the approach and you’ll rely on them to confirm that you’re solving the right problem.

This is very important. If you get the framework correct, then solving the case interview question can be reasonably straightforward. If you get the framework wrong, you’ll almost never solve the case.

Step 4. Test each component of your framework

Now is the most challenging part. It’s time to break down the business problem.

As I mentioned earlier, your framework should cover all the potential hypotheses for the business problem. So if your framework is good, then it’s simply a matter of working through and testing each step.

Start the first step of your framework and ask your interviewer questions to understand that aspect of the business. For example, you might want to start answering your profitability case question by breaking down revenues. In that step, you would ask questions about revenue drivers, such as average sales price, number of units sold, etc.

From there, work through each step of your approach. In our example, you would then ask questions about costs, such as changes in fixed costs, variable costs, etc.

At this stage, you’re looking to identify root causes. In many cases, there will be multiple root causes, so don’t stop when you’ve found one potential root cause. Continue until you’ve worked through your entire framework.

Once you’ve finished working through your framework, ask your interviewer if there’s anything else that you should consider. Follow their lead. If all goes well, there won’t be anything that you haven’t already investigated.

Step 5. Synthesize findings and draw conclusions

At the end of the interview, you’ll need to describe your findings and provide recommendations to the client.

You probably have a whole bunch of different findings and root causes for the business problem, so you need to make sense of it all.

Ask the interviewer if you can take some time to prepare your findings for the client. They will always give you this time.

Step 6. Communicate your recommendations

It’s important that you clearly, concisely, and confidently communicate your recommendations to the interview.

You should use the Pyramid Principle to structure your recommendations, which means:

• Start with the recommendation: Start by stating your main recommendations for the business. This should only be a few sentences.
• Follow with the rationale: Describe the main arguments for your recommendation. These arguments should be supported by data and other evidence.
• Focus only on what’s important: Ignore everything else. Don’t discuss anything that you’ve found to not be the cause of the business problem.

Other tips for the case interview

It goes without saying that the most important thing is to answer the case question well.

To do that, you should follow the approach outlined above. But, in addition, you should:

• Ask questions: Never be afraid to ask questions. Treat your interviewer like a consulting client. Your job as the consultant is to ask them questions to understand the root cause of their business problem.
• Take logical notes: Case interviews can take up to 45 minutes and it’s impossible to keep everything in memory for the entire time. Your interviewer will expect you to write things down. And they sometimes even judge the way that you write notes, so keep things neat and logical.
• Stay composed: You’ll almost certainly run into a dead-end and not know where your line of questioning should go next. Don’t panic! Just take a deep breath, review your notes, and move on.
• Demonstrate structure: Consultants love structure. You should show that you have a structured approach that you’re following methodically. And, whenever you’re listing or grouping, you should ensure that your items are MECE (mutually exclusive, collectively exhaustive).
• Communicate top-down: Whenever you need to communicate something with the interviewer (e.g. your recommendation), you should start with the conclusion and then follow with the justification. This is known as the Pyramid Principle.

Example case interview questions

Example 1: Healthcare (McKinsey & Co)

Our client is Magna Health, a health care company in the Midwest. It both insures patients and provides health care services. Employers pay a fixed premium to Magna for each of their employees in return for which Magna covers all necessary health services of the employee (ranging from physician care, and medications to hospitalization).

Magna currently has 300,000 patients enrolled in its plan. It has 300 salaried physician employees who provide a broad range of services to patients in 6 centers. These physicians represent a wide range of specialty areas, but not all areas. When a patient needs medical treatment in a specialty area not covered by a Magna physician, they are referred outside of the Magna network for care, and Magna pays all referral costs on a fee-for-service basis. Magna does not own any hospitals itself, instead contracting services from several local hospitals.

Magna’s CEO has retained McKinsey to help determine what is causing the declining profitability and how Magna might fix it. What key areas would you want to explore in order to understand Magna’s decline in profitability?

Example 2: Banking (Bain & Co)

Our client, Giant Bank is one of the “big 4” banks in Australia. These 4 banks account for about 75% of the retail/commercial banking revenue in Australia and are roughly equal in size. Giant Bank does not have a good understanding of the profitability of its retail customer base, and more specifically individual segments.One segment that has been of particular concern to them is the “youth” customer segment. This group encompasses all customers under the age of 22.

Giant Bank wants Bain to help answer two questions:

1. What is the average annual profit of a Youth customer?
2. What should Giant Bank’s strategy be to maximize long term profits for this customer segment?

Example 3: Private Equity (Bain & Co)

Gulf Partners, a private equity fund specializing in leveraged buyouts, has asked Bain to evaluate an investment in Singapore-based Acme Packaging. (A private equity firm is a company that has raised money from individuals and institutions to invest in companies that may be a riskier investment but offer the promise of higher returns.)

Acme Packaging manufactures and sells intermediate bulk containers (IBCs), which are metal frame crates stacked within shipping containers for the transport of goods. Acme Packaging has manufacturing operations in Singapore and sales offices throughout Asia. 100% of sales are from Asian markets with 80% of sales from rubber customers – mostly tire manufacturers from Japan and Southeast Asia. Acme Packaging has 65% market share within the rubber IBC market and has increased share in the Asia IBC market by 5% over the past 3 years.

Gulf Partners prefers to sell their investments within 5 years with a minimum 40% return on their investment. In order to evaluate whether Acme Packaging can generate high returns, Gulf Partners would like Bain to assess the growth potential for Acme Packaging. They specifically want to know:

1. Can Acme Packaging double its operating income by year 5 (2006)?
2. What growth opportunities should Gulf Partners pursue to increase the value of Acme?

Example 4: Medical Devices (BGC)

Your client is GenCo, a large, international, diversified company with a health care division that produces a wide variety of medical instruments and related services.

Five years ago, it expanded into the health care software industry by purchasing MedCount, which markets administrative systems to large U.S. hospitals. These systems are designed primarily for back-office functions; they are not designed for managing patients or providing other physician and technical support.

Since it was purchased, the software division has failed to deliver the growth needed to justify the multiple GenCo paid for it. GenCo feels it has already squeezed margins as much as possible, and now is looking for new sales opportunities.

MedCount turned to BCG to help identify potential ways to increase revenues. How would you approach this problem?

Example 5: Defense (BGC)

Your client is a U.S. defense contractor that manufactures the Mohawk Light Fighter Jet for the British Royal Air Force. The company has produced the $20 million fighter jet for the past 12 years. The British government has decided to put the contract out to bid, however, and to win the program, the client’s purchasing agents have estimated, the company will need to cut its costs by 5 percent. It has asked BCG to help it reduce costs.

Example 6: Foods (BCG)

Your client is the sugar cereal division of Foods Inc., a U.S.-based distributor and manufacturer of packaged foods. According to the division president, Foods Inc.’s traditional strength has been with grocery stores, which still account for the majority of its $1.1 billion in sugar cereal sales. But Big M Mart, a discount chain, has been growing at a healthy rate of almost 15 percent per year and has now become Food Inc’s largest customer. Your client is not sure how to react, and has asked BCG for assistance with its distribution strategy.