You can use the given common formula to convert your SGPA (Semester Grade Point Average) into a percentage:

Percentage = (SGPA * 9.5)

Example:

Semester 1 - 8.77 SGPA
Percentage = (8.77 * 9.5) = 83.31%
Semester 2 - 7.64 SGPA
Percentage = (7.64 * 95) = 72.58%
You should note that though this formula is very common your university might have its own percentage calculator formula then you can use it.