ISI Kolkata M.Tech CSE cutoff for a direct interview is 770/1000 in GATE. But scoring 770 doesn’t guarantee that you will be able to get an interview call. Shortlisting for interviews is done based on the competition that year.
For written tests, ISI does publish a cutoff. Recent years’ record shows the required cutoff for MMA > = 51/120, and MMA + 2PCB > = 117/320, for general category students. To get a shortlist based on interviews, general category students need around 190/480. Naturally, the required cutoff changes each year.
The cut-off varies every year depending on the difficulty of the paper. It cannot be predicted exactly but it can be analyzed on the basis of the previous year’s cut-off.
Let me tell you that one of my friends got 82/120 in MMA, and attempted 84/100 in PCB Computer Science. His interview did not go well. He was asked two questions and he panicked. One was based on graph theory and mathematics combined; the other was a question on Binary trees.
As my friend did hold 12th rank but from this, you can roughly guess how much you need to attempt. It is tough out there but doesn’t be worried, just do your studies nicely and honestly. With all your preparation you will be good.