Convert your letter grades for each class into a numerical value. Most schools use a 4-point grading system. In this case, an A is equivalent to 4 points, a B is equivalent to 3 points, a C is equivalent to 2 points and a D is equivalent to 1 point.
Multiply the numerical conversion by the total semester hours for each class. For example, if you receive an A in a four hour class, you would multiply 4x4 to get a total of 16. Do this conversion for each class you are taking.
Add up the total grade points from Step 2 for all of your classes in a semester. Divide this number by the total semester hours to determine your GPA for a semester. For example, if your total grade points for a semester are 53 and there are 15 hours in the semester, your GPA would be 3.5.
To determine your cumulative GPA, add up all of your numerical grades from each semester or from multiple years and divide the number by the total hours for each course over that period. For example, if in your first semester you have a total of 90 grade points and 25 semester hours, your cumulative GPA is 3.6.