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Can I round numbers during Mckinsey online interview?

Is it bad if I round my numbers during the math part of the case? How is it seen by McKinsey interviewers?

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Evelina
Coach
9 hrs ago
EY-Parthenon (6 years) l xBCG l 97% success rate l 30% off first session l free 15' intro call l LBS

Hi there,

Rounding numbers during a McKinsey interview is perfectly fine and even encouraged, as long as you do it strategically and transparently. Clearly state when and why you’re rounding (e.g., “I’ll round 983 to 1,000 to simplify”), and avoid extreme rounding that affects accuracy.

McKinsey values practicality and efficiency, so rounding shows strong problem-solving skills when done appropriately. Just ensure the final result is directionally accurate and avoid rounding for critical or already simple calculations. Focus on clarity and logic—exact answers are less important than your process!

Best,
Evelina

Mattijs
Coach
9 hrs ago
Free 15m intro call | First session -50% | Bain Consultant | Hiring team | 250+ successful candidates

Hi,

It's very common to round numbers during calculations. Rounding is especially helpful during case interviews where you're expected to quickly analyze data and arrive at estimates. Note you always mention you are rounding numbers and how it influences the final result.

I recommend to do some daily math drills to further sharpen this skill.

Good luck!

Mattijs

Matthew
Coach
17 hrs ago
Ex-BCG R1 Case Interviewer | Former Campus Recruiting Captain | Focused coaching to accelerate offline case prep

Hi there!

It's good practice in general (whether for online or in-person case interviews) to ask the interviewer before rounding any numbers. 

Rounding numbers isn't seen as a "bad" thing in and of itself, but communicating what is going through your head (e.g., that you want to round a number and your reasoning why) helps the interviewer understand your thought process. This is important because an interview is ultimately testing not just if you can do the math or not, but how you guide someone else through your thinking- something that is directly applicable in client facing work (e.g., if you had to walk a client through your calculations). 

One strategy that I've found helpful is to set up the structure of the calculations you want to do, tell the interviewer the correct numbers you would use with examples, and THEN ask if you can round the numbers. For example you could say:

  • It sounds like we want to calculate Revenue. I can do that by multiplying price per unit by number of units sold
  • To do that calculation, I would need to multiply the price of $10.99 by the 149,000 units sold
  • To simplify the math while getting us to an approximately correct answer, I would want to round the price to $11. I would also round the number of units sold to 150,000 to start, before deducting 1,000 units multiplied by $11 or $11,000 from the final answer to find revenue at a price of $11 for 149,000 units
  • Does this approach make sense to you and are you aligned with me rounding the numbers this way?

With the above approach, you do 2 very important things:

  1. You show the interviewer that you've broken the math down and you conceptually understand how to calculate the correct answer. This helps build their confidence in you because your reasoning is easier to follow and understand
  2. You've broken the math down into easier to calculate steps for yourself and you've given the interviewer an opportunity to give feedback (important for more complex calculations than the example above) while also asking if rounding would be appropriate 

Remember that a case interview involves two-way communication and that interviewers are generally there to support you in the problem solving process. Not sure if you've landed an online interview but fingers crossed for you and all the best!

Maria
Coach
17 hrs ago
Ex-McKinsey Engagement Manager in NYC | Part of the McKinsey Private Equity Practice

Hello!

Yes, you can round numbers during McKinsey online (or in person) interviews. If you want to feel more comfortable, you can confirm with the interviewer to which degree you should round.

Good luck!

Maria

Thabang
Coach
9 hrs ago
Ex-McKinsey Consultant | McKinsey Top Coach & Interviewer | Special Offer: Buy 1 Session Get 1 Free (Limited time!)

Hey there, 

The short answer to this is to check with the interviewer first. Sometimes cases advise you to round, other times they want to test your arithmetic ability

Before requesting to round, state your approach and show what operations you want to do with your numbers. Or once you've done the calculations, ask if you can round for sake of simplicity - and also state that it won't make a material difference (and bonus points if you can state the impact range of that rounding)

7 hrs ago
#1 Coach for Sessions (4.500+) | 1.500+ 5-Star Reviews | Proven Success: ➡ interviewoffers.com | Ex BCG | 10Y+ Coaching

Hi there,

Q: Is it bad if I round my numbers during the math part of the case? How is it seen by McKinsey interviewers?

In general, if you ask in advance if you can round a number, there are no problems with it. The interviewer might ask to use the exact numbers, but you won’t be penalized for asking.

Best,

Francesco

Alessa
Coach
3 hrs ago
xMcKinsey & Company | xBCG | +200 individual & group coachings | feel free to schedule a 15 min intro call for free

hey!

Yes, rounding numbers is generally acceptable during McKinsey interviews, as long as you clearly communicate your approach and ensure it does not significantly impact the accuracy of your analysis. Interviewers typically appreciate a balance between speed and precision. If rounding helps you move through the problem efficiently while maintaining logical consistency, it's seen as a positive approach. However, avoid excessive rounding that could lead to major deviations from the correct answer.

A good practice is to state your rounding assumptions aloud (e.g., "I'll round 4.87 million to 5 million for simplicity") to show structured thinking and transparency.

Alessa

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