Hello Sourav,

The admission authority will release the cutoff for top B.Tech branches of NITs for the admission of candidates in different NITs through JEE Main. 

Factors determining the NITs cutoff for top B.Tech branches

• Total number of applications received for the admission in the institute
• Total number of candidates appearing for the JEE Main exam
• Number of B.Tech seats available
• The difficulty level of the JEE Main 2019 exam
• Previous years’ cutoff trends

I would suggest you visit the careers360's link given below for detailed info of the cutoff

The link for the same is:https://engineering.careers360.com/articles/nits-cutoff-for-top-btech-branches

Hope this helps and all the very best!