For calculating the percentile from the raw score,we need to know to few things which are.

1. First we should know the number of candidates appeared for exam in the shift. Let us denote this but by N.

2. Then all the candidates of the shift are sorted in decreasing order of their marks.

3. Then raw score of each Candidate is noted. Let denoted by T. Then number of candidates in that shift whose raw score are equal or less than T are counted . Suppose this number is m .

4. Then percentile score of calculated as

P =[ m÷N]×100

Hope it would help you