The highest possible grade point average on a 4.0 scale is a 4.0. While most schools use the 4.0 GPA, some schools use a Quality Point Average which weights advanced classes higher than a 4.0.
Under a 4.0 GPA system, each class is awarded a point value based on the grade in the course. For example, an "A" grade awards four points per credit, a "B" grade awards three points per credit, and a "C" grade awards two points per credit. To calculate a GPA, multiply the number of credits for each course by the number of points awarded. Then, divide that number by the total number of credits.