Complete a semester or year's worth of courses and know their mark in letter grade. Once a student has her marks she must calculate the quality points she has achieved and divide them by the quality hours, or number of credit hours, the college has assigned the course.
Attach a numerical value to the grade; for example, according to Harvard Universities letter grade index, A = 4.0, A- = 3.67, B+ = 3.33, B = 3 C+ = 2.33, C = 2, C- = 1.67, D+ = 1.33, D = 1, D- =0 .67 and F = 0.
Not all colleges follow the same letter grade system, so students should search their college's website to be certain.
Multiply the numerical number by the amount of credits a course is worth to calculate the quality points earned; for example, if a student received an B+ in a course worth 8.1 credits, he would multiply 3.33 (B+ = 3.33) by 8.1: 3.33 x 8.1 = 26.97. Thus, the student has received 26.97 quality points for the course they have completed with a grade of B+.
Calculate the GPA for the entire year or semester by adding the quality points for each class completed, like in Step 3.
Add all the quality hours amassed over the semester or year. Each course is given an amount of quality hours by the college and the student should add all the hours complete for the semester so he has a total amount of quality hours.
Divide the amount of quality points by the amount of quality hours to calculate GPA. For example, If a student has earned 45 quality points over 15 quality hours, she would divide 45 by 15 and would have a GPA of 3.0. This process can be used to calculate the GPA for one course, a semester, a year or the entirety of a degree.