The percentile rank of a score is the percentage of scores in its frequency distribution that are equal to or less than it. The percentile rank formula is used to find the performance of a student in a class of 100. To calculate percentile rank, you need to know the score, the mean, and the standard deviation. You can use the percentile rank formula to find the percentile rank of any score. If you have questions about percentile rank, you can ask a math teacher or tutor for help.