Obtain from your school registrar your transcript and the school's list of grade-point equivalents. This list will show the point value of each grade. Typically an A is worth 4 points, a B is worth 3 points and a C is worth 2 points.
Multiply each course grade grade-point equivalent by the number of credits you received for that course. If you received an A in a three credit course, multiply 4, the grade-point equivalent, by 3, the number of credits to calculate 12, the total grade points for that course.
Add together all of the grade points. Divide by your total course credits to calculate your cumulative GPA. If the total of your grade points is 90 and you have taken 30 course credits, your cumulative GPA = 90/30 = 3.0.