The 4.0 grade point average scale is an unweighted numeric value representing a student's academic achievement level that is obtained by converting a student's letter grade into grade points and then averaging the points into a single value. Each letter grade from A to F corresponds to a particular value between 0 and 4, so calculating a student's GPA involves adding the grade points from each of his classes and dividing that figure by the number of classes taken.
Each letter grade translates to a different numerical value: A is 4, A- is 3.7, B+ is 3.3, B is 3.0, B- is 2.7, C+ is 2.3, C is 2.0, C- is 1.7, D+ is 1.3, D is 1.0 and F is 0. After adding the numerical value for each separate letter grade up, the resulting sum is divided by the number of classes taken. For example, straight A's in four classes and a B in one class translates to a total value of 19. Divide 19 by 5 classes to get 3.8, which is the overall grade point average.
Some academic institutions use a weighted GPA system where more advanced classes are given greater weight in the overall average. This system typically goes up to 5.0, and advanced classes are given an extra half or full point. This means that an A in an advanced class in a weighted GPA system is equal to 4.5 or 5.0 rather than 4.0.