What is the minimum score required to get admission for B.Tech in IIT?

Actually, it does not depend on the score. It depends on the rank you get in the JEE Advanced exam which depends on the cutoff that varies every year depending on the level of difficulty of the question paper.

It depends on the cut-off score. The level of question paper also plays a very important role. The subject-wise cut-off is also there. One cannot simply decide about the minimum score.