Determine the GPA you are trying to achieve; a 3.0 is one example.
Calculate the number of classes you are taking during the term for which you want to determine your GPA. Most high school students take six to seven classes.
Note the GPA-equivalent numbers that are associated with each grade. According to the International Student Guide, the American grading system designates the letter grades A, B, C, D and F, which are given the numerical values of 4.0, 3.0, 2.0, 1.0 and 0.0 respectively.
Multiply the GPA you hope to achieve by the number of classes you have. For example, 3.0 X 7 = 21.
Determine a combination of seven of the GPA values that equal 21. You will get multiple combinations. For example, 4.0 + 4.0 + 3.0 + 3.0 + 3.0 + 2.0 + 2.0 = 21. This means you can get an A, A, B, B, B, C and a C to score a 3.0 on your GPA. Another combination could be all Bs, which would equal the equation 3.0 + 3.0 + 3.0 + 3.0 + 3.0 + 3.0 + 3.0 = 21.