Well for CSE, there is variation in closing rank among different IITs, For Top IITs like Bombay, Delhi, Kanpur You must have a rank within 100, i.e AIR under 500. For new IITs, You can get CSE at category rank of around 1500 Or AIR under 7000.

CSE in rest of all IITs will be between these two extreme ranks so If you able to get a rank under 7000AIR then you possibly you will get some IIT.

You can refer to the opening-closing ranks of JoSAA.