Hello Mukesh!

Your Btech marks cutoff for admission into IITs vary from one IIT to another.
For example the eligibility criteria for IIT Bombay is:-

Academic Qualifications :

Candidates applying must have secured at least 60% marks for general and obc category and 55% marks for SC/ST category candidates in their B.E./B.Tech/B.Sc. (Engineering)/ M.Sc./MCA/MBBS/M.Pharm/B.Pharm (4 year degree)/ BDS (4 year degree) qualifying degree.

You need to check the eligibility criteria for every IIT Accordingly.
You can search for all this information about every IIT on careers360 itself.

Hope this helps :)
Best of luck!