GPA is calculated as sum(grade_point_value*units)/sum(units). For example, if a student got an A in a 4-unit class and a B in a 2-unit class, the GPA of the student should be (4.0*4+3.0*2)/(4+2)=3.67.

Major GPA is calculated in the same way as GPA except that only the courses from the student's major are included in the calculation. For example, suppose a CS student got an A in a CS class and a B in a Math class, the student's major GPA would be 4.0.