Hello Sagar, 

Admissions in NIT's are done on the basis of the rank secured in the JEE MAINS. This rank is determined by the percentile which is a measure of your performance with respect to other applicants. It tells you about how many applicants are equal or below you.

You can predict your rank from the following careers360 link below. 

https://engineering.careers360.com/jee-main-rank-predictor?icn=JEE_Main_rp&ici=JEE_Main_article_view_sticky

Closing rank for NIT, Calicut is 13365 for home state (HS) quota, while for other state (OS) quota it is 8022 for the general category. Similarly for NIT, Tiruchirapalli HS is 6667, OS is 2461. For NIT Durgapur, HS is 19524, OS is 12249. For NIT Surathkal, HS is 6413, OS is 4064. For MNNIT Allahabad, HS is 7361, OS is 7286. For NIT Silchar, HS is 57639, OS is 21354. For NIT Rourkela, HS is 10644, OS is 5494. For VNIT Nagpur, HS is 11501, OS is  7994. For SVNIT Surat , HS is 18259, OS is 9808. For NIT Warangal, HS is 5470, OS is 4299.

These are the 2018 cut off's of top 10 NIT's across India. For cut off's of other NIT's you can refer to the following careers360link.

https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-cutoff/amp

Hope this information was helpful.

Thank you.

All the best!