The default average and standard deviation is an approximation to recent national numbers, and may be changed to match what is displayed on a student’s individual Step 1 score report, or approximated to USMLE World displayed averages for a given exam.
Keep in mind that the 2-digit score is neither a percentage nor a percentile. It is the NBME’s own scale that was historically used to help set a passing rate, and there are rumors that it is in the process of being discontinued altogether. It is also important to note that the NBME purposefully withholds information on percentiles from medical students taking the USMLE board exams, as they specifically state on their site:
Percentiles are not provided in connection with USMLE scores. The calculation and provision of data to be used to rank or make comparisons among examinees is inconsistent with the primary goal of USMLE, which is to provide a series of assessments and recommendations for minimum passing requirements to the state licensing authorities to support decisions about initial licensure. Furthermore, normative data such as percentiles are easily misinterpreted because, as the examinee group changes across time, the correspondence between percentile values and examinee ability can change. For these reasons, USMLE does not report percentiles.
After reading all of the above disclaimer, consider yourself thoroughly warned about the implications of using the calculator. It is recommended, when coming across someone who is not familiar with this policy, to direct them to posts such as this, or the NBME site directly, instead of actually providing them with a less-than-appealing percentile. Nevertheless, some scholarships and other applications require the value, despite the misunderstanding. With all of the above disclaimer, MedStudentBooks.com is hesitant to provide an online USMLE Step 1 3-digit score-to-percentile converting calculator.