I have got total 51 percentile. So what is my score?

Hello. Your marks is difficult to predict from your percentile. This is because suppose you score 300 out of 360 which is the highest in your session then your percentile will be 100. And suppose another person scores 350 out of 360 in another session then his/her percentile will also be 100. So a same percentile does not mean the same marks.

You can check out your rank from the below formula.

Rank- (100-your percentile)*(874469/100)

But this rank will differ because it depends on your percentile which ultimately depends on no. of students appearing for JEE mains April exam. According to previous years cutoff ranks, any rank below 2,00,000 will be good to qualify for JEE Advanced. To know the exact rank you will need to wait till the April exam after which NTA will declare the overall merit list based on the best of two attempts and tot. no. of students.

I would recommend you to study well and sit for the April attempt and try to score a percentile of 70+. Your best of two attempts will be considered while declaring your rank.

or more details check the below link.

Https://www.entrance360.com/engineering/how-to-calculate-rank-for-jee-mains-2019/

Hope this helps. For any other questions feel free to comment down below.