Expert with best answer


97% Recommendation Rate

364 Meetings

5,229 Q&A Upvotes

USD 229 / Coaching

When is it OK to estimate? Is a fast estimate better than a slow but accurate answer?

Anonymous A asked on Apr 03, 2018 - 2 answers

I understand that it is generally OK to estimate when you are using a calculation to get a Y/N answer (i.e. determining whether to proceed/not proceed based on being above or below a specifc target).

Other than this situation, is it OK to round or estimate your answers to get an approximate answer more quickly? Do I need to ask the interviewer every time I want to round or estimate slightly [e.g. rounding (155 million / 206) to (155 million / 200)]?

Also, if specifc answers are required, what level of precision is generally acceptable? One decimal place?

2 answers

  • Upvotes
  • Date ascending
  • Date descending
Best Answer
replied on Apr 04, 2018
McKinsey / Accenture / Got all BIG3 offers / More than 300 real MBB cases / Harvard Business School
Book a coaching with Vlad

97% Recommendation Rate

364 Meetings

5,229 Q&A Upvotes

USD 229 / Coaching


  1. Ask the interviewer 1-2 times to get a sense of how comfortable he is with rounding numbers and how many zeroes he requires.
  2. Continue with an assumption that you should keep that level of preciseness throughout the case. Worst case - he'll tell you to change the approach


Anonymous replied on Apr 04, 2018


First, I would never estimate (other than direct market sizing questions!) without asking first if the interviewer has such data available. If he doesn’t have it, then it’s a hint that you might need to estimate.

Second, you should never make approximations without asking if you can do it. You’ve no idea which skills the interview is trying to test, if it’s pure math, you don’t want to be the person who decided to simplify all the math (ask also about the decimals, but it’s rare to have cases working with decimals)



Related BootCamp article(s)

How to Read Charts and Data in Case Interviews

We explain and give tips on how to understand and analyze graphs, charts and data presented by interviewer to candidates in case interviews.


Why Math matters

Your math skills will be tested in each and every consulting interview. So you better brush up mental math skills to succeed.


Fast Math: How to Master Mental Math

Apply these tips and tricks for outstanding mental math shortcuts to impress your interviewer in your next case interview.

Typical Question Types in Written Tests

Questions among all tests can be categorized in math, GMAT-style, chart reading and brain teaser questions. Each type needs to be approached differently.

Guide to Improving Speed in Written Tests such as the PST

Follow these instructions to significantly improve your performance and speed in solving problem solving tests used at McKinsey, BCG and Bain.

Related case(s)

Airline Economics

Solved 11.7k times
4.3 5 515
| Rating: (4.3 / 5.0)

We are an airline major operating out of India. We want to increase the number of passengers on all our flights. Could you please calculate the financial return of adding one more passenger per flight? Open whole case

REA Reinsurance

Solved 9.5k times
4.1 5 906
| Rating: (4.1 / 5.0)

Your client, REA, is a reinsurance company. REA recently acquired another reinsurance company (approximatively same size): the choice of this company was notably based on its product portfolio as well as its market presence which appeared complement with REA. However, the acquisition is not well r ... Open whole case