When and how to use a GMAT diagnostic test - MBA Prep Tutoring

When and how to use a GMAT diagnostic test

GMAT diagnostic tests are an important part of your GMAT preparation, but they have a place and time. In order to get the most out of them, I want to share some tips.


Should you do an initial diagnostic test?

It's very popular that students do an initial diagnostic test in order to have a "base score". I think the only case in which it's worth doing this test is if you are really strong in one area and want to know if you should focus solely in Quant or Verbal first.

In Quant for example, an engineer can take a diagnostic test and let's say the result is a 49 in Quant (out of 51). What that would mean is that maybe he or she doesn't need to take a Quant course and should focus only in Verbal.

Something similar would happen in Verbal, if a lawyer for example takes a diagnostic test and scores 43 in Verbal, this person is pretty much set in Verbal and should only do Quant.

Scores that are near or below average wouldn't indicate "specific areas" to focus on, because there are many factors that could give you that score. In Quant specially, it might be that the test taker simply doesn't know how to analyze Data Sufficiency questions correctly, or runs out of time. In these cases I recommend just starting with a GMAT Prep course from zero. If the student is good in certain areas, it will become apparent during the classes and they will flow faster.

Factors to analyze in a diagnostic test

Once you take a diagnostic test, there are many factors that contribute to your score:

  • Number of mistakes (there is a range for each score)
  • Level of difficulty of each question
  • Mistake distribution
  • Questions without answering

Something that is not taken into account is the time per question. You can get a correct answer in 5 seconds or 5 minutes and it will mean the same for the algorithm.

I know it's easy to see your score and just think "I should practice more". But it's really important to reflect on all the questions, not just the ones you have wrong. Always ask yourself "how can I do this faster?"

What usually happens when reviewing your test is that about 50% of incorrect questions shouldn't be wrong in the first place. Either because you made silly mistakes or if you tried again with more concentration you got to the answer with no problem. So you should only get a question wrong only if you still get it wrong outside of the test.

It goes without saying that you should answer all the questions, even if you are running out of time. The penalty for not answering questions is greater than having them wrong.

How frequently should you take a diagnostic test?

As with any skill that you try to improve, there should be significant work done between taking tests. It's not recommended that you take practice tests in consecutive days just before the official test.

There should be at least a few days in between, a week if possible. Also consider taking 3 or more tests before the official test. That means that you should finish reviewing all the concepts and formulas at least a month before the official test.

What you want to focus on between tests are the following:

  • Getting comfortable with timing your practice sessions per question.
  • Deepening your understanding of concepts, formulas and properties.
  • Reviewing past questions, specially those that were incorrect at first.
  • Practicing quality question from official sources (Official books, question banks).


Diagnostic tests should be used as a measure of how much you improved, not as a tool to improve. Beware of using all your tests available too soon. If you have a plan you will be able to get the most out of them.