Percentile score is based on the performance of candidates who have appeared for the exam. to calculate the rank we need the following formula.

((100-P/100)*N+1). For example JEE Main 2020 rank = (100 - your total score)*874469/100

To convert a percentile score the Mark's are converted into scale ranging 100 to 0 for each session. To calculate the percentile into rank you need the following figures.

1. Your NTA score.

2. Total number of students who have appeared for the exam.

3. Percentage of students below or equal to your Mark's.

4. Percentage of students above your Mark's.

5. No of students above your Mark's.

I think this will help you to calculate your score.

To compute the JEE Main percentile score, you'll need the following information:

• The total number of applicants who took the JEE Main exam in a given session.
• A candidate's highest raw score in that JEE Main session.
• Note that a candidate's raw score will differ from his or her percentile score. The percentile score is not the same as a candidate's proportion of marks.

The formula for calculating the JEE main percentile score is as follows:

• 100 divided by the total number of candidates who took the JEE Main exam in a certain session with a raw score less than or equal to the candidate who received the highest raw score divided by the total number of candidates who took the exam in that particular session.

You can also refer the below link

https://engineering.careers360.com/articles/jee-main-normalisation-process-how-scores-are-calculated