For NITs, only JEE mains is accepted, and the cutoffs close down to 10,000 rank for JEE MAIN and hence beyond such ranksyou have less chances to make through.

For IIts, you need to also appear for JEE advanced alongwith JEE mains.

For all top IITs like Madras, kharagpur, bombay, delhi, Kanpur, Hyderabad you are supposed to be under AIR 9000 for JEE Advanced to get any of the branches at above colleges.

You can get complete details about closing ranks for all IIT s and the respective branches as per 2017:-

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

To get admission in NITs your rank should be under 50,000 in general category other state quota. Cut off rank varies according to the branches.

To get admission in IITs your rank should be under 9800 in general caregory.

Make sure you fulfil minimum eligibility criteria to get NITs and IITs that is 75% marks in yor boards exam or you should be in top 20 percentile.

Good Luck!!