Sort the data from smallest to largest
Count the total number of values, n
Find the percentile rank position using: p = (percentile / 100) × n
If p is a whole number, take the average of the values at positions p and p + 1
If p is not a whole number, round up to the next whole number and use that position
For a specific value, find how many values are below it
Divide that count by the total number of values
Multiply by 100 to get the percentile rank
Use interpolation if your method requires a value between two positions