Hi

Eligibility criteria says that to be eligible  for JEE mains 2021 for BE or Btech you just must be either appearing for 12th board exam in 2021 or should have passed it in 2020 or 2019 with Physics,  mathematics and anyone of Chemistry or Biology or Biotechnology or Technical Vocational Subject.

There's no percentage barrier to be eligible for JEE mains

But yes,

In 2021 , to be eligible for NITs, IIITs, GFTIs , jee advanced( for iits) one needs at least  75% marks in aggregate in class 12 if belong to general or obc category or at least  65% marks if belongs to SC/ST or  must be in the top 20 percentile in  class 12 examination.

Thank you