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You can Not calculate Your Percentile score on Your own Because Percentile Tells Your relative Position and Without considering the Performance of the Other students You can not calculate the Percentile Scores.

For calculation of the Percentile Scores Following formula Were Used By NTA.

Total Percentile (T1P): 100 X (No. of candidates appeared from the session with raw score EQUAL TO OR LESS than T1 score/ Total No. of candidates appeared in the session)

Mathematics Percentile (M1P):100 X (No. of candidates appeared from the session with raw score EQUAL TO OR LESS than M1 score in Mathematics/ Total No. of candidates appeared in the session)

Physics Percentile (P1P): 100 X (No. of candidates appeared from the session with raw score EQUAL TO OR LESS than P1score in Physics /Total No. of candidates appeared in the session)

Chemistry Percentile (C1P): 100 X (No. of candidates appeared from the session with raw score EQUAL TO OR LESS than C1score in Chemistry/ Total No. of candidates appeared in the session) 

For complete Details Of Normalization Please visit the Link Given Below:

https://jeemain.nic.in/WebInfo/Handler/FileHandler.ashx?i=File&ii=4&iii=Y

Hope this Helps All the Best.