A grade point average system works by assigning a numerical value to each letter grade, multiplying this value by the number of credit hours for the course, adding the values together and finally dividing the sum by the total number of credit hours attempted. Most schools use a system where the highest possible score is 4.0 for an A, and the lowest possible score is 0 for an F, though there are many variations to this system.
A common grade point average system variation awards different numerical values based on whether the student receives a plus or minus letter grade. For example, a regular B is worth 3.0 points under this variation, a B-plus is worth 3.33 points, and a B-minus is worth only 2.7 points.
Another common variation is a weighted grade point average system. Weighted systems are only common in some high schools, while nearly all colleges and universities use the standard four-point system. Under a weighted system, a student who takes more challenging or difficult courses has an opportunity to earn a higher grade point average than students taking regular courses. For advanced placement, honors or other challenging courses, the usual numerical value for grades increases by one point. For example, a student who earns an A in a traditional calculus class earns 4 points for each credit hour, while a student in honors or advanced placement calculus earns 5 points.