Convert CGPA to percentage and percentage to CGPA (×9.5 rule), and calculate a credit-weighted GPA on the 4.0 scale.
The CBSE rule is Percentage = CGPA × 9.5, so a CGPA of 8.4 is about 79.8%. Many universities use their own multiplier or formula, so the multiplier is editable. Use the one printed on your mark sheet or set by your university.
A GPA is a credit-weighted average of grade points on a 4.0 scale: each course's grade points × its credits, added up and divided by total credits.
CBSE found that, on average, students' percentages were about 9.5 times their grade points, so it adopted 9.5 as the conversion factor.
Using the ×9.5 rule, 8 × 9.5 = 76%.
At some US schools it does; most cap it at 4.0. This calculator uses 4.0.