Does 12 marks matter in IIT?
The clear answer is NO. Class XII marks do not affect JEE Mains ranking in any way. Some years ago, they were added to calculate the rank but now it has been changed. I do not know why you need to ask this question as you should be aware of this fact.
Anyway, the Union Ministry of Human Resource (HRD Ministry) has decided that Class XII marks will not be a factor in determining rankings in the Joint Entrance Examination (JEE) for admissions to engineering undergraduate courses from JEE Mains 2017.HRD Ministry officials said the decision was taken by the Ministry after a committee set up by IIT Council submitted recommendations on
changes in the JEE pattern, which were put in the public domain for wide consultations.
To qualify for appearing in the exam, students need to have at least 75 percent marks or be in the top 20 percentile in the Class XII examination. That’s the eligibility for JEE Advanced. Still, I recommend having a decent percentage is good and useful.