Convert your percentage grades into letter grades. A grade of 90-100 equals an A, 80-89 equals a B, 70-79 equals a C, 60-69 equals a D, and less than 60 equals an F.
Calculate the number of grade points earned. For each class in which you made an A, add 4 points for each semester hour. Each B is worth 3 points per hour, each C is worth 2 points per hour, each D is worth 1 point per hour, and each F is worth 0 points. If you took five three-hour classes and made four As and one B, Multiply 4x3 for each A, for a total of 48, and 3x3 for the B, for a total of 9. Adding 48 and 9 gives you 57 grade points.
Total the semester hours. Five three-hour classes total 15 semester hours.
Divide the number of grade points earned by the number of semester hours to find your GPA. Dividing 57 by 15 yields a GPA of 3.8.