Case Interviews for Consulting Jobs: How to Prepare and Answer with Structure

How to prepare for consulting and strategy case interviews: common case types, a 5 step answer structure, mental math, and a practice plan you can follow.

You sit across from the interviewer and they say: "Our client is a coffee chain in Thailand. Profit has fallen for two years in a row. How would you help them?" No questions about your resume, no "what are your strengths". Just one business problem and a blank sheet of paper. This is the Case Interview, a format used by consulting firms such as McKinsey, BCG and Bain, as well as by in-house strategy teams at many large companies in Thailand. Candidates who have not practised often freeze or talk in circles. Those who practise systematically stay calm, think in steps and communicate clearly.

What is a case interview, and what does it measure?

A case interview asks you to solve a simulated business problem live, together with the interviewer. The goal is not the "right" answer, because most cases have no single answer. What they look for is:

• Structured thinking: can you break a big problem into parts that do not overlap and cover everything (MECE)?
• Business sense: can you make assumptions that fit a real business?
• Accuracy with numbers: can you calculate under pressure and check your result?
• Communication: can the listener follow you, and do you end with a usable recommendation?

Common case types

Cases candidates meet most often

• Profitability: why profit fell, and whether to fix revenue or cost
• Market entry: should the client enter a new market, for example Vietnam?
• Growth strategy: how to keep growing from the current base
• M&A: should the client buy or merge with this company?
• Pricing: how to price a new product
• Operations: how to make a process faster or cheaper

There are also market sizing questions, such as "estimate how many cups of coffee are sold in Bangkok per day", which directly test your assumptions and arithmetic.

A 5 step answer structure

1. Listen and clarify: restate the problem in your own words and ask about the objective, e.g. "Within how many years does the client want profit back to its previous level?"
2. Build a framework: ask for a moment to think, then walk through your structure branch by branch.
3. Analyse each branch: ask for data, form hypotheses and say what you are testing.
4. Synthesise: connect the data into an insight, e.g. "The main issue is rent at the new branches."
5. Recommend: give a specific recommendation, the risks, and what should be checked next.

An opening line you can use

"Let me confirm: the client is a coffee chain, profit has fallen for two years, and they want to know why and what to do. May I take a moment to structure this? I will look at two sides: revenue, split into number of cups and price per cup, and cost, split into ingredients, labour and rent. Shall I start with revenue?"

Frameworks: a skeleton, not a script

• Profit = Revenue minus Cost: the base of almost every profitability case
• 3C (Customer, Company, Competition): for market entry and growth
• 4P: for marketing and pricing cases
• Porter's Five Forces: to judge how attractive an industry is

Experienced interviewers spot a pasted framework immediately. It is better to tailor the branches to the case. For the coffee chain, use branches like "sales per branch" and "number of branches" instead of broad generic headings.

A good case interview is not about guessing the right answer. It is about leading the listener through structured thinking to a recommendation they can act on.

Mental math

• Round numbers so they are easy to work with, and tell the interviewer you rounded
• Work in thousands and millions, and count your zeros carefully
• Break big calculations into small steps and write them down
• Sanity check before you answer, e.g. is the result bigger than Thailand's population?
• Always say your assumptions out loud

A few minutes a day of multiplication, division and percentage drills will keep you calm when real numbers appear.

Mistakes that fail candidates

• Starting the analysis before clarifying the objective
• Using a rigid framework that does not fit the case
• Making a calculation error and not checking it
• Ignoring data or hints the interviewer gives along the way
• Ending with a vague line such as "they should increase sales" without saying how

How to start preparing

1. Read a foundation book such as Case in Point by Marc Cosentino, which McGill University's career centre lists as a case interview preparation book.
2. Practise alone with a timer: write your structure, record yourself and listen back.
3. Find a case partner and take turns being the interviewer several times a week.
4. Talk to seniors working in consulting, or find a mentor at Plants.work Mentors.
5. Practise communication and general questions in Interview Lab, since real interview rounds usually include experience questions alongside the case.

Case interviews are a skill you can train, not a talent you are born with. The more varied the cases you practise, the faster and more natural your structuring becomes. Read next: the last 24 hours before an interview and practising interviews with ChatGPT and Claude, then browse open strategy roles on the job search page.