For candidates in the Open (General) category, most engineering entrance exams and colleges require a minimum of 45% aggregate marks in Physics, Chemistry, and Mathematics (PCM) in Class 12. This is the basic eligibility for applying to B.Tech or B.E. programs across many states and universities. However, for more competitive institutes or specific streams, higher percentages may be expected for actual admission, especially when seat allotments are based on merit. It's important to note that simply meeting the minimum percentage doesn't guarantee admission—it only makes you eligible to apply.