Hello
for Old IITs you need atleast around 400 rank to get IIT in colleges like IIT Bombay or IIT Kharagpur and for new IITs like IIT Gandhinagar you need atleast 3000 rank to get CSE.
To know more : https://engineering.careers360.com/articles/iits-cutoff-for-b-tech-computer-science-and-engineering.
Hope this helps.
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