Generally IIT entrance exam is nothing but  combination of JEE and JEE advance exams.To crack these exams you need to cross the cut off marks which is listed on website and it's according to the category (General/OBC/SC etc)you belong .

The cut off marks doesn't vary more with respective to last year but keep the aim high that is above the cut off so that you can crack it .

In JEE mains, you need to secure the cut-off. Rest IIT selection entirely focuses on JEE advanced results.

Regarding JEE advanced, you need to under 34k (for a general category) to be eligible for counseling.

Now I tell you a dark secret, your eligibilty has o value if you are not getting a seat at a college.

Even I've secured under 10k rank but still sitting in a NIT (though among the top NIT's :P)

So it is my sincre request to focus on getting a rank atleast under 7k to hope for a seat at better IIT's.

For this you need to secure around 30-33% of the total marks considering the new subjectivity of the paper and my best of knowledge.

All the best for the exam