Hello

The top 20% of class 12th boards considered for  the admission to 31 NITs,23 IITs and 23 GFTIs. For the joint entrance examination, the students are required to score 75% or above to enter top 20 percentile of their respective boards to be eligible.here  are the cut off marks of general category stood at 66.8% and it followed by 65.2% for other backward class(obc),63% for scheduled caste(sc) and 62.8% for St.here is the link to get more information

https://engineering.careers360.com/articles/top-20-percentile-cutoff-of-class-12-boards-for-iit-admission

All the best