Hello,
If you want to get admission in IIITs/NITs/IIITs then you need to score atleast 75% aggregate marks in class 12th board exams.
For top private colleges you need to score atleast 60% in class 12th board exams and for other private colleges 50% will be enough.
Good luck.

In jee mains 75% is needed (65% for SC & St)

Otherwise most of the exam demand 65% or 60%  in pcm..

Maybe you are asking for score needed for admission in btech.Most of the time it is more than 55% some also take admission only for more than 65% and so on criteria increases.