Evaluating GMAT scores is a massive source of confusion especially as it relates to GMAT percentile scores. Let's start from the basics. The most important sections on your GMAT are the Quantitative and Verbal reasoning sections. For each of these sections you'll receive scaled GMAT scores.
What's a GMAT scaled score?
A scaled GMAT score provides an absolute measure of skill. Eh? Think of it as how much weight you can lift. Got a GMAT Quant scaled score of 45? That means you can lift 45 units of quant. That measure doesn't change from year to year. Lifting 45 units of quant is the same today as it was 10 years ago. Both verbal and quant scaled scores range from 0 to 51. On quant a 45 or above is very good, 48 and up is great, and 50+ you're a whiz. On verbal high 30's is solid, 40 plus is great and makes 700+ very accessible, 42 and up opens the door to mid 700 scores, and 45+ is the 99th percentile.
GMAT Percentile Score
On that note, your GMAT score also includes a percentile score. The GMAT percentile score is a relative measure of your ability versus that of other GMAT test takers in the last three year period. GMAT percentile scores change. A quant score of 45 used to be in the 80th percentile now it's in the 55th percentile. A composite score of 750 used to be the 99th percentile. Bad news for 750 people out there: you've been demoted to the 98th percentile! Not a big deal because percentile scores are secondary to your composite score and scaled score. Absolute measures make it easier to keep things stable over time. Here's an in depth discussion on GMAT percentiles and how you can be admitted to Harvard with a failing GMAT Quant percentile.
Integrated Reasoning and Essay scores
The integrated reasoning also has a scaled and composite score. The scaled score is from 1 to 8.
The essay also has both types of scores. The scaled score is from 1-5.
Again, important thing to remember about GMAT scoring: Integrated reasoning and essay don't count towards your composite score and are barely factored into admissions decisions (as of 2018). The two scores that count are the Quantitative and Verbal reasoning.
What's a good GMAT score?
A good GMAT score is the one that gets you into your desired MBA program. OK, Mr. Smarty Pants, how do I know ahead of time what GMAT score will get me into a great MBA program? Check the median GMAT scores at your top choices. Ideally you're at or above the median. Do I have to be at or above the median GMAT score to be admitted? No, certainly not. Look at the score range. There were people admitted with GMAT scores way below the median. However, consider that for every point below the median on your GMAT score you need to make up a point elsewhere on your application. Those points don't necessarily need to be earned by volunteering to build wells in an underserved community. They can also be earned because you have a a diverse background or are from an underrepresented group.
What's a good GMAT quant score?
The GMAT Quant score does have a bit of influence so if you knock it out of the park and say have a 700 with a 51 quant 39 verbal that might be a little better than a 710 with a 42 quant 45 verbal. Also, regardless of the composite score there is a danger area for quant scores. Below 40 and you'll likely need to show some quant skills either through undergraduate course work, work experience, or post graduate classes. I'd say quant 44 or below you may also be under scrutiny. What about the 80/80 rule? If someone tells you that you need an 80th percentile quant score to receive admission to a top MBA program that person has no clue what they're talking about and are operating on 10 year old ideas. GMAT Quant percentile scores have changed drastically over the past 10 years so now a 60th percentile quant score is more the cutoff. For the GMAT verbal that's somewhat valid. You probably do need 80th percentile plus on verbal but that more relates to the composite score in that you can't achieve the median at most skills without at least an 80th percentile verbal score no matter what the quant.
GMAT Score Report
Your GMAT score pops onto the score right after you finish your GMAT. It's quite a nerve wracking but thrilling moment. That score though and the print out given to you at the test center are unofficial GMAT scores and don't include the score on your essay. The printout includes the scaled and percentile scores for Quant, Verbal, and Integrated reasoning. While it is only an unofficial score report most schools allow you to add unofficial scores to your application and then follow up with the official GMAT scores once they can be transmitted.
Enhanced GMAT Score Report
While we're talking about GMAT scores it seems remiss not to mention the ESR. GMAC holds back most of the useful diagnostic information for your GMAT scores and sells it back to you as your Enhanced GMAT Score Report (ESR). This report started off really crappy. It had almost nothing that was worthwhile. It's been upgraded several times through the years and at this point the ESR is useful as it provides not only information about your timing during the test but also scoring by content.