Obtain your grades from each class for the semester. Say you have five classes, three are AP classes and you've gotten an "A" in each class.
Provide each letter grade with a numerical value. The typical GPA converter scale is:
A = 4 points
B = 3 points
C = 2 points
D = 1 point
F = 0 points
For AP classes you add an extra point to each letter grade, with the exception of "F." AP class scales are as follows:
A = 5 points
B = 4 points
C = 3 points
D = 2 points
F = 0 points
Add your grades. You have five "A" grades, three of which are AP grades. This means you have two "A"s worth four points each and three worth five points each for a total of 23 points.
Divide your 23 points by the number of classes you're enrolled in to obtain your GPA. In this example, you'll divide 23 points by five classes for a GPA of 4.6.