Teachers will often use weighted percentages to assign different significances to different assignments. For example, a teacher might want to place more emphasis on students doing well on the final than on the two other tests during the class. If your class uses a weighted percentage system, you need to know the value of each of the assignments and how well you did on each assignment to figure out your grade for the class.

Divide each weight expressed as a percentage by 100 to convert to a decimal. For example, if your first test is 20 percent of your grade, you would divide 20 by 100 to get 0.2. If your second test is worth 30 percent and your final test is worth 50 percent, you would divide 30 and 50 by 100 to get 0.3 and 0.5.

Multiply each grade by its weighted percentage. If you scored 95 percent on your first test, you would multiply 0.2 by 95 to get 19. If you scored 80 on your second test and an 88 on your final test, you would multiply 80 by 0.3 and 88 by 0.5 to get 24 and 44.

Add the results from step 2 to find the weighted average. Here, you would add 19 plus 24 plus 44 to find your average to be 87.