Hello,

The minimum Education qualification required to appear for CAT entrance examination is Bachelor's Degree in any discipline from a recognised board. The candidates belonging to general category must score minimum 50% aggregate marks in the qualifying examination and for SC/ST/PWD category candidates it is minimum 45% aggregate marks. Candidates who are studying in the final year of the qualifying examination are also eligible to apply provisionally.

Diploma is equivalent to 10+2 so you can fill the marks scored in Diploma as you have scored highest in Diploma than in class 12th as there is weightage for academic performance. You need to be in the final year of UG course or must have completed the course to appear for CAT. In case if you are still studying in B.Tech (2nd or 3rd year) then you are not eligible to apply for CAT. If you are in the final year of B.Tech then you can apply for CAT and the marks scored in B.Tech uptil the semesters for which results are announced are considered to determine the minimum percentage criteria.