Find your grades for each class and how many credits the class is worth. For example, assume you took four classes. Each class is worth three credits. Your grades were A, B, A- and B+.
Convert your letter grades to number grades. Usually the conversion is an A is four, B is three, C is two, D is one and F is zero. If you have a +, then add 0.33 to your grade. If you have a -, then subtract 0.34 from your grade. In the example, your conversions are 4, 3, 3.66 and 3.33.
Multiply your number grade by the credit hours, then add the results together. This calculates quality points. In the example, 4 times 3 equals 12, 3 times 3 equals 9, 3.66 times 3 equals 10.98 and 3.33 times 3 equals 9.99. The sum of the results equals 41.97.
Add together the total number of attempted credit hours. In the example, there are 12 credit hours attempted.
Divide your quality points by the attempted credit hours to calculate your GPA. In the example, 41.97 divided by 12 equals a GPA of 3.4975.