Question

how to calculate percentage from cgpa

Answer 1

Multiply overall CGPA by 9.5
i.e. 7.8* 9.5 = 74.1%For subject wise percentage, multiply grade points received in each subject with 9.5.

Answer 2

for each subject, one receives a grade like A+, A-, B+, B-, C+ C-, D etc.
For each grade there is a weightage mentioned:  like 10, 9, 8, 7, 6 ... on 10...

so if one got A+, +B, C+ , A-, B-, C-   respectively in 6 subjects,
         then CGPA = [10 + 8 + 6 + 9 + 7 + 5] / 6 = 7.50  on 10

Then the percentage is simply:  CGPA * 10 % = 75 % for  the above set of grades.

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If the weight of the top grade is mentioned as 4.0, then the percentage will be calculated as  :  CGPA * 25 %