Hi,

The cutoff depends on many factors like number of student applied, number of seats available, difficulty level of exam, marks obtained etc.

Every  IIT has its own opening and closing rank. So depending on these factors the cutoff marks vary from year to year.

In previous years the jee advance cutoff for sc category was minimum aggregate 17.5 percentage. And minimum 5 % in each subject.

So you should score an aggregate  percentage near around 16 -25% to be safe to secure seat in IITs.

Hope it helps.