hello aspirant,

You did not mention which exam are you talking about.but in your profile as you are an engineering aspirant assuming you will be giving your jeemain.percentile is the no.of Candidates who scored better than you in the exam.To calculate your JEE percentille, we should use the formula 100 - your total percentile score.  for example in 2020, 869010 Candidates appeared for January exam.so, your rank formula  is (100 - your total score) X 869010 /100. you can change the total students appeared in each session,by changing the 869010 number in the above formula.

for easy analysis you can refer to: https://engineering.careers360.com/articles/jee-main-marks-vs-percentile

if its about any other exam please let us know and feel free to ask any query

hope this helps,

thankyou.