Check with your school's office or university registrar to find out what numerical amounts are associated with different letter grades. For example, some schools assign numbers to As through Fs, with As being 4.0 and Fs being 0. Other schools may assign pluses and minuses, with an A+ being a 4.33 and a B- being 2.67.
Multiply the numerical amount associated with the grade by the number of hours of the course to obtain the grade points for the class. For example, if the course was credited with three hours and the grade received was a B, which in most grading systems is equal to a 3.0, then multiply 3 by 3.0 to get 9.
Add all the class grade points together. For example, if the grade points for the classes are 12, 9, 9 and 3, then those numbers added together equal 33.
Divide the total number of grade points by the number of hours attempted. Courses that earned an F, or 0, should be counted in the number of hours attempted. Check with your school to see whether withdrawn courses count toward the number of hours attempted. For example, if 12 hours were attempted or credited for the semester and you earned 33 points, then 33 divided by 12 equals 2.75. The GPA for the semester would be 2.75.