Suppose you know, or at least you suspect, that you want to go to business school at some point in the not-too-distant future. You know that you have to take a GMAT at some point and you want to get some idea about how long you should study for the GMAT.
Factors to consider
One factor to consider is your history of performance on standardized testing in general. For example, I have always performed well above the 95% percentile in standardized testing, so the first time I studied for the GMAT, I studied for only about two weeks and scored a 770. This is probably not to be taken as exemplary for all students. Let's say that if you know your percentile rank from some previous standardized test (SAT, ACT, etc.), then as a very rough estimate you could use this scale to approximate what a GMAT score of the same percentile would be.
You should also consider your relative strengths. If you spent your undergraduate years studying something intensely mathematical, then probably your math skills will be in good shape for the GMAT. If your undergraduate degree is in something that involved a great deal of reading, writing, and arguing, then perhaps the verbal section will be more intuitive for you. In particular, if English is not your first language and if you are anything less than 100% fluent in it, I would highly recommend studying the English language in general and the GMAT verbal section for as much time as possible.
Finally, you should have some idea of the schools to which you may be applying ---- even if that's a few years away. Even if you have no idea where you will apply, visit a few school websites and get a sense of the lay of the land. If you have any inkling that one particular school might be of interest to you, check it out. In particular, find out their application deadlines (likely to remain approximately the same from year to year), and a general ballpark idea of the GMAT scores needed to get into these schools. The former will give you some sense of time, and the latter will give you a rough sense of what kind of GMAT score you may need.
If you are just finishing your undergrad degree, and know that you will work for at least two years before you go to B-school, in some sense you have the luxury of time on your side. I would recommend: even if you are going to do intensively practice over, say, a three-month period leading up to your projected GMAT date, consider starting "lightweight" practice now --- for example, every day, read at least one article on this blog (present or past), and do the practice questions, learn the strategies. If math is a weakness, force yourself to do some mental math every day. If verbal is a weakness, read one hard article every day. Start to get yourself warmed up, so that you get the most out of your more intensive period of review.
So far, much of what I suggest in the above paragraph involves pure estimation. At some point, to give yourself a much better idea of how much time you need to practice, you should take a practice GMAT. The GMAC website offers free test prep software, but I would strongly recommend NOT practicing on the official material until you are toward the end of your studying, ideally immediately before you take the real GMAT. For this first trial-run estimate, the actual quality of the GMAT matters considerably less. We highly recommend that MGMAT books, and the Kaplan book is not too bad ---- it's certainly much better than the Princeton Review book, the Barron's book, or the Peterson's book. I actually would say: the MGMAT material and tests are so good that you should also save them for later in your practice. You need a quick low-quality test just to estimate at the beginning. You may buy a Kaplan book, purely for the practice test. You may also find a free test given in one of the two forums, GMAT Club and Beat the GMAT. (If you don't know about those two free forums, they are both excellent places to learn all kinds of facts about the GMAT and find out about all kinds of resources.)
Get some kind of practice GMAT, take it more or less cold, and score it. That will give you a rough idea about where you are starting, about your baseline. Figure that, with concerted preparation, you will easily do 50 points, maybe even 100 points, higher than your cold performance. Estimate that one month of reasonably solid prep could get produce an improvement in that range, and that for more significant improvements, you will need both more time and more intensive review.
As a very rough estimate --- generally, a score is considered minimally competitive if it is over 650 (78th percentile). The better schools generally require something over 700 (90%), and the very top tier schools usually require something at the very elite level of 750 (98th percentile) or above.
Keep in mind, also, that GMAT score is only one factor among many in B-school admission. Undergrad GPA, work experience, recommendations, and how you package yourself as a candidate are all important: some of those will already be set, but consider to what extent preparation for the GMAT might detract from some other aspect of the application. A stratospherically high GMAT score of 780 will not get you into any particularly impressive schools if you have essentially no work experience.
How to improve?
OK, now suppose you have taken your practice GMAT, and you know your cold-sitting baseline score. It may be that you are close to where you want or need to be, and that would be just dandy. It may be, though, that you want to reach for substantial improvements in your GMAT score. Moving up 100+ points is big, and moving up 200+ points is HUGE, but it can be done ---- it will just take sustained and focused effort. First of all, notice that the right sidebar on this blog lists GMAT study schedules: even if you aren’t ready to start studying right at the moment, it would be a good idea to peruse these, to get a sense of your options and the work involved. I would highly recommend the MGMAT series of books: whatever volumes you think you need to shore up your weaknesses, or perhaps the whole set of ten; many of our GMAT study plans involve some or all of these books. I would highly recommend reading through this free blog, trying the practice problems, and starting to learn strategy: even if your formal study period is a few months away, checking out an article or two on this blog every day could be an excellent warm-up. Finally, to get the most from your GMAT studying, I would recommend investing in Magoosh: we have over 200 lesson videos, covering all the math & verbal content & strategies you need; we provide quick email support to all questions about our material about the official materials; and we offer 800+ GMAT practice questions, each with its own video explanation for accelerated learning.
Also, once you've figured out exactly how long you'll be needing to study, we have a whole set of study schedules to keep you on track.
For practice, here's a GMAT Data Sufficiency question:
Here's a practice Critical Reasoning question:
For each one of those, after you submit your answer, the following page with have both a video explanation and a text explanation.
This post was written by Mike McGarry, GMAT expert at Magoosh, and originally posted here.