what could be the least ranking to join iit colleges ?

General branch wise rank list for a few top-IIT branches is as follows:

• CSE - AIR < 500. (net score > 70% of max marks, achievable by MINIMUM -ve score and CORRECTLY SOLVING ALL THE EASY AND MODERATE QUESTIONS THAT MAKE UP ~80% OF THE PAPER).
• Maths and computing - AIR < 1000. (comparable to, and less preferable than dual degree CSE).
• Electrical/Electronics - AIR <1100. (Net score >60% of max marks ).
• Mechanical - AIR < 2000 (Net score >= 50% of the paper.)
• Civil - same as mechanical, maybe only slightly less.
• Aerospace (at IIT K/KGP/B/M) - AIR
• <3000. (Net score ~50% of max marks).
• ALL DUAL DEGREE PROGRAMS - slightly greater ranks (maybe a few hundreds more) than respective normal courses.
• Chemical - AIR < 2500. Same as aerospace, maybe slightly more.
• Engineering physics/Textile/Production & Industrial Engg/Bio Tech/ Manufacturing/ Mining/ Metallurgy - AIR 4k-8.5k (mostly neglected and less sought after branches).