Minimum qualification marks in 2018 was (-35) under PwD category 

However cutoff is higher than qualifying marks at all NITs depending on various streams and quoats. 

Generally scores above 40 to 60 marks also convert NIT as lowest possible. 

With marks above 150 in PwD Category, students can get awesome prospects of top NIT and Top Branches.

Detailed cutoff reports on rank basis below. 

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