Hello. It is difficult to say exactly from which percentile onwards you can qualify for JEE MAINS before the April exam because NTA will declare the overall merit list on the basis of best of two attempts and no. of students appearing for the exam. 

However for now you can know your rank by the following formula

Rank=(total number of students -(percentile*0.01*number of students))

Tot. No. Of students- 9.75 lakhs

For further information check the below links.

https://engineering.careers360.com/articles/jee-main-result

https://engineering.careers360.com/articles/jee-main-normalisation-process-how-scores-are-calculated

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