Hello
Your son's JEE Mains score is really good.!
He can easily get admission in any of the Bestt NITs.
As per your question, its difficult to predict the rank or the qualifying percentile score for JEE Advanced level as for now. So you will have to wait. The final cutoff percentile score and ranks will be released later after the April exam.
Well, you can calculate the approximate rank by the below given formula:
(100 - your percentile) - (874469/100)

Here, 874469 is the total number of students who appeared in the January exam.

The approximate rank comes  nearly to 7000 and it may vary a bit depending upon the number of students appearing for the April exam.
Hope this helps.!
Good Luck.!!

Hi

Wow that is a great,  and amazing percentile.  Not only he is qualified for JEE Advanced but also he can get into top NIT,  IIITs. 

When it comes to rank it is difficult to predict the rank as of now.  Because NTA gives rank based on both the exam. Main and advanced. 

However you can calculate your approximate rank based on below formula

((100 – P)/100)*N + 1

P is your percentile

N is total number of candidates

8.74 lacks 

Put the no and get your rank

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