The MCAT consists of three multiple-choice sections (Physical Sciences, Biological Sciences and Verbal Reasoning) and a writing assessment.
Each multiple-choice section is scored from one to 15, with 15 being the highest. The writing sample, on the other hand, is given letter scores from "J" to "T" with "T" being the highest score.
Medical educators scoring the MCAT count the number of correct answers in each section and convert the raw scores into a scale that takes into considerations the difficulty of test questions.
Educators score each writing essay twice and your total raw score on the writing sample section is the sum of the four individual scores given to the two essays you wrote in the MCAT. Each individual score ranges from one to six ,and the total raw score is then converted to an alphabetic scale.
Since only correct answers count towards your score in the MCAT, there is no penalty for guessing.