Choose one subject to add together the grades received for all grading periods. For example, if the school system has four nine-week grading periods, add together the grades for the first, second, third and fourth nine-week periods for Reading. Use a calculator if needed. The Online Calculator website has one that can be used for the task.
Divide the sum of the grading periods by the number of grading periods there are. For example, when you add 85, 81, 86 and 88 together, the sum is 340. There are four grading periods in this example, so divide 340 by 4.
Calculate the answer. For example, 340 divided by 4 is 85. Eighty-five is the final report card average for that subject.
Repeat the process for other subject areas.
To find the overall grade point average (assuming all subjects are ranked equally by the school or district), add together the average of each subject and divide by the number of subjects.