Empirical Rule percentiles are the percentage of data below (to the left of) an x value. Use this Quick and Easy calculator to find percentiles when you are given the population mean and standard deviation and x values. In most intro stats classes, you will only be given x values whose z-scores are integers. If a problem has x values whose z-scores are not integer values, you can find percentiles using the Normal tab on the workbook. See below for links to download the workbook.