Many schools use a standard four-point GPA system where each A is worth four points, each B equals three points, each C equals two points, each D equals one point, and each F equals zero points. The total is divided by the number of classes the student has taken.
Some schools use a weighted GPA instead of a standard four-point system. In a weighted system, extra points are given for grades earned in honors or advanced placement classes.
The decile system shows which tenth of the class the student falls in based on his GPA. For example, if the student's GPA put him higher than 94 percent of his classmates, he would fall in the first decile.
The decile system is sometimes used in place of class rank so colleges can estimate where in the class the student fell. Colleges take the performance relative to the rest of the class into consideration because different schools have different grading systems.
Deciles can use weighted or unweighted GPAs. Some schools list your decile based on both your weighted and unweighted decile to show colleges the effects of weighting on your class rank.