Dear Aspirant,

The formula you have mentioned is correct. It doesn't matter how many subjects you have. It's a general formula. The only change which might be possible is that instead of 9.5 it could be 9.6. You will find this on the internet as well. It doesn't make much difference. In university exams as well we calculate our percentage by multiplying by 9.5.
This is the demerit of the CGPA system. It doesn't give much value to toppers. All the students who have secured 95% and above will secure 10 cgpa.

I hope this helps.

Good Luck