Best IIT college in Many ranking is IIT Bombay, Now cutoffs are different for Different courses and different categories, Since You does not mention any Branch and category, You can go to the opening-closing rank portal of JoSAA which will help you to determine the rank you need to get into the desired course. Here is the link:https://josaa.nic.in/webinfocms/Public/View.aspx?page=71

Note that This rre the ranks Not marks because marks vary every year according to the difficulty level.