Well, we have our general GPA which is calculated the same way in every department I think (don't know about other universities though), and then we have our engineering GPA which I don't think people care about as much, but it's still a thing.
Regular GPA is based on your grade and credit hours. So, an A corresponds to 4.00, A- corresponds to 3.67, and so on. You multiply that by the number of credit hours you got for a course in order to get the total grade points for that particular course (e.g. a 3 credit hour course in which you get an A contributes 12 grade points). Do that for every course and then divide by total credit hours for GPA.
So like this semester I had 13 credit hours total. My grades looked like this:
Calculus (4 hrs): A
Intro to Comp (3 hrs): A
Shakespeare (3 hrs): A-
Intro to EE/Circuits (3 hrs): B+
So it was like [(4*4)+(3*4)+(3*3.67)+(3*3.33)] / 13 ≈ 3.7692
Engineering GPA I don't feel like explaining, read this if you want (also explains regular GPA): https://www.engr.utexas.edu/undergraduate/forms/6086-calculating-your-engineering-gpa I don't really get what makes a good engineering GPA but whatever.
Your school should probably have a page that explains it to you, if you haven't looked for that.
@wolffange, I'll get to responding to your post soon.