Hello

We can not calculate exact marks from the percentile score. 

As percentile score is relative score depend upon number of students who score more than you and total number of students.

Example: if you score 200 marks and number of students who score more than you is 20 out of total 100 

And second case if you score 250 marks but the number of students who score more than you is same 20 out of 100 than your percentile is same in both the case.

So it will depend upon the exam difficulty level and in that particular slot it is equal for all.

And there are different sets of papers also and their difficulty level may differ  so percentile score equalize all the sets .

I think you got what I am saying.

Good luck.

Hello!! 

as per your percentile, your marks may be between 1-70. Use our links https://engineering.careers360.com/articles/jee-main-marks-vs-rank , https://engineering.careers360.com/articles/jee-main-rank-predictor ,  https://engineering.careers360.com/jee-main-rank-predictor for your complete reference. Input you percentile and know your rank too by using the above links. 

all the best!!!