A student recently wrote questioning why his GMAT score was lower than expected based upon the number of questions he missed in the quantitative section and his sectional scores. We replied with the following explanation.
It’s important to understand that due to the rounding and ten point segmentation the GMAT uses when calculating sectional and total scores from your raw score, the real scoring algorithm commonly produces a slightly different total score for the same pair of sectional scores and vice versa. For example, it is not an error to see one student earn a total GMAT score of 580 paired with a 35 verbal and 35 math and to also see another student earn a total GMAT score of 570 paired with a 35 verbal and 35 math. This is due to the fact that your total GMAT score is not calculated directly from your GMAT section scores. Instead, both your total and sectional GMAT scores are derived from your underlying raw score.
Moreover - the location of your mistakes within the test are critically important in determining your score. A miss near the beginning of a section is a much higher deduction than a miss at the end of the section. This is another reason you can’t easily compare results based solely on “number of missed questions” - I hope that sheds some light on scoring within the GMAT. Best of luck in your preparations!