Market Sizing and Guesstimate Questions – Consulting Case Interview

The magical approach and killer tips & tricks to solve any Guesstimate and Market-sizing questions in any consulting Case Interview.

For Market-sizing questions, it doesn’t matter what each specific question ask. Every question is extremely similar in term of the approach.

Consulting Case interview market sizing questions

Interviewers often spontaneously make up market-sizing question like this. So there’s no point of learning a number of specific questions. It’s way more important to learn the method.

For more FREE practice material: Case Interview Home & 101 Video – Management Consulting Prep

Presented by Kim Tran, a former McKinsey consultant and the founder of the platform: Management Consulting Prep 

5 Bad Habits That Are Harming Your Business

“Habits form from repetition and frequency. case study interview The problem is that most people repetitively implement the wrong [habits] that are actually blocking their success,” says Walker. 



1. Failure to delegate. “You can’t be everything to your business,” says Walker. mckinsey interview Sure, you can cram in an 80-hour workweek, but you likely won’t be able to keep up that pace. Invest in the best people you can afford, delegate tasks that match their expertise and trust them to do their job. This will allow you to focus on what you do best and the company to run smoother.

2. Bottlenecking decision-making.  mckinsey case interview “Entrepreneurs like to have control,” says Walker, but forcing every decision pass through your office can cause your business to slow down, frustrating not only your employees but your customers as well. By hiring the right people and ensuring everyone is clear on the overall goals, you’ll allow your business to thrive.

3. Being reactive instead of proactive. Setting your sights to the future is the key to any business’ success, unfortunately Walker meets many entrepreneurs who don’t plan ahead. “Strategic thinking is what you need in order to have the right habits,” says Walker. mckinsey case studies Once you have goals, you can create habits that reinforce these goals and set you on the path to achieving them.

4. Engaging in unproductive activities. consulting resume Walker says email and Facebook are the worst offenders in this category. “[People think] they’re being productive and multitasking where in reality I believe that the whole idea of multitasking is unproductive,” he says.  Make it a habit to only check your email two or three times a day and plan ahead for your social media time.

5. Fear. Walker says the worst habit that an entrepreneur could have standing in the way of productivity is fear. Fear of failure, making a decision, and of upsetting others can quickly erode your productivity and business success. “Fear actually takes time,” he says. Focusing on your fear takes time away from making important decisions that will propel your business toward achieving your goals.

If you recognize any of these above habits in your business, it’s time to take action. Walker says exchanging negative habits for positive ones begins with assessing your current situation. “If I have a result that I don’t want, the first question I have to ask myself is how did I get there,” says Walker. The next step is to write down the habits you want to get rid of and make goals that will get you to where you want to be and review these goals daily. mckinsey resume

Walker says it takes 21 times of repeating an action for it to become a habit. Creating a vision board or reviewing your goals every day for 21 days will cement them in your subconscious and become a habit. “Once your goals become habits, everything starts to fall into place,” says Walker.


Great sources to learn about McKinsey bussiness case interview

Some pdf guide, limited source of info but basic, needed, worth your time:
– EXBD guide
– PITT guide

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Some Oldie classic practice blogs that everyone have heard of:
– Consulting success
– Prep lounge
– Mconsulting Prep
– Ace the case
– Consulting case 101 (many case studies)
– Case
– Management

And of course, official guide from McKinsey, Bain, BCG, etc

Market Sizing – Guesstimate Case Question Tips and Tricks

One of the most commonly asked questions in Consulting Case Interviews are Market Sizing and Guesstimate. Read  Market Sizing & Guesstimate 101 article if you need some basic knowledge. But let’s get right into it, what are somesimple tips and tricks that significantly boost up your performance?

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1 – Spend a little time for CLARIFICATIONS at the beginning
In most Market-sizing and Guesstimate questions, there are always unclear areas. You should develop a habit of always starting off with clarification questions. Not only it helps clear out gray areas but also helps you score points in the overall interview. Even if these gray areas turn out to be ok, the interviewer will like you, just by having those clarifications in your approach.
2 – Breaking down the big problem into MANAGEABLE pieces
You probably know that the key to answer these questions is to break them into smaller pieces. However, you should be smart in how you do that. Mis-breaking down problems may kill yourselves with the complexity. Normally, only 1 or 2 layers down from the original question is fine. The components must be easier to estimate than the original question.
3 – Suggest EASE-to-calculate numbers in your assumptions 
Similar to the above, no need to kill yourselves by coming up with difficult numbers. Just suggest simple, round numbers to the interviewer and most of the time he / she will be ok with it.
For example: If there is a question needs to start off from the USA population, don’t use 314 million, just say 300 million … In special occasions where the interviewer really wants to test your quantitative skill, then you have to be precise. But don’t go into it because most of the time it is unnecessary.
Side-note: Boost up your Number speed and accuracy with our free Consulting Math materials and drills
4 – Always ALIGN assumptions with your interviewers
In the process of solving any Market-sizing and Guesstimate questions, you use assumptions. The killer tip is to pass the danger part to the other side of the table. Aligning every assumption with the interviewer is the way to get him / her also be responsible for the final result.
In addition, similar to #1 above, most interviewers will like candidates who align often. It is a good habit in real consulting jobs. An analyst may be exceptionally smart, but he will not do well without constant guidance and help from managers.
5 – SANITY check along the way and especially the final answer
Even though the final answer is not very important in this type of question, it would not be nice to have an unreasonable answer. Here is an example:
After rigorous analyses, you come up with the final answer to the question “How many Chinese use iPhone”: 9 billion … If you don’t realize there is some wrong with this number before giving it to the interviewer, you are in trouble.
Similar to the above, the habit of sanity check every number will score points for you. Interviewers love it, just like how they love their young consultants do sanity check on real data and analyses.