Hello

It would be difficult to calculate the marks from the NTA score. JEE Main result released by NTA is available in the form of score card containing four NTA scores in the form of percentile for Physics, Chemistry and Mathematics and total score.

Calculation of exact rank is difficult. However, you may calculate the expected rank using the formula mentioned below-

100 - your total percentile score is the percentage of people ahead of you. 869010 are the number of candidates appeared for Jan exam.
So rank formula is (100 - your total score) X 869010 /100.

If the number of candidates for April exam increased to 1200000 then your final rank shall be (100 - your total score) X 1200000/100

Do let us know if you have any other queries.

Good Luck!