New MCAT Test Scores
The MCAT is a scaled exam, meaning that your raw score will be converted into a scaled score that takes into account the difficulty of the questions. There is no guessing penalty. Because different versions of the test have varying levels of difficulty, the scale will be different from one exam to the next. Thus, there is no "magic number" of questions to get right in order to get a particular score. Plus, some of the questions on the test are considered "experimental" and do not count toward your score; they are just there to be evaluated for possible future inclusion in a test.
At the end of the test (after you complete the Psychological, Social, and Biological Foundations of Behavior section), you will be asked to choose one of the following two options, "I wish to have my MCAT exam scored" or "I wish to VOID my MCAT exam." You have five minutes to make a decision, and if you do not select one of the options in that time, the test will automatically be scored. If you choose the VOID option, your test will not be scored (you will not now, or ever, get a numerical score for this test), medical schools will not know you took the test, and no refunds will be granted. You cannot "unvoid" your scores at a later time.
So, what's a good score? If your GPA is on the low side, you'll need higher MCAT scores to compensate, and if you have a strong GPA, you can get away with lower MCAT scores. But the reality is that your chances of acceptance depend on a lot more than just your MCAT scores. It's a combination of your GPA, your MCAT scores, your undergraduate coursework, letters of recommendation, experience related to the medical field (such as volunteer work or research), extracurricular activities, your personal statement, and so on. Medical schools are looking for a complete package, not just good scores and a good GPA.