Calculate the percents if they are not given. The percent calculation divides the score or number by the possible score or number. For example, if a student gets a 28 out of 30 on a test, he would divide 28 by 30 to get a total score of 93.3 percent on the test. If the percent is already given, use the number provided.
Add all of the percentages together. For example, if you have 93.3 percent, 89 percent, 95.5 percent and 90 percent on four quizzes for a class, you would add the four scores to get 367.8.
Divide the number found previously with the number of percentages added. For example, 367.8 is divided by 4 to find the average percent of 91.95 for the student's tests. If you need a round figure rather than a decimal or if the decimal for the average percentage is a repeating decimal, round up to the next number if it is .5 or higher or round down if it is .4 or lower. For the student who received 91.95, his rounded average percentage is 92 percent.