Hi student,

Your percentile is 82. It means 82% students of the Total students appeared for the Exam are Behind you. Therefore Your calculated Approximate rank is 157404.

However this is not your final rank. Whether you have qualified jee mains and are  eligible for jee advance or not will depend upon whether you have crossed the cutoff marks declared by NTA officially. This cutoff will be different for different categories of students. As of now, the cutoff have not been declared and reportedly will be declared after the jee mains exam in April. 

However you cannot calculate your marks from the percentile. But you can know your marks by comparing the answers given by you during the examination with the official answer key released by the NTA. You get +4 marks for correct answer and -1 for wrong answer and 0 marks for unattempted questions.

Good luck.