Guneet, 

There's no such way to calculate marks from percentile. The paoer was held in different times and different days everybody paper was different so it is impossible to predict marks from rank or percentile.

But you can go to official website of jee mains login with your application No.  And password /dob and check your score there. 

Go to the link given below 

http://jeemain.nic.in/jeemainresult/root/authcandwithdob.aspx