Sometimes teachers make mistakes, which is why it is important that you are able to calculate your final grade in a class on your own. You will need a complete list of your grades in each weighted category of the class in order to accurately compute your final grade. These categories most commonly are homework, tests, and quizzes. Sometimes teachers use special projects or class participation in addition. Computing your final grade consists of finding your average in each category, then multiplying it by the percentage of the class it's worth and adding all the adjusted categories together.

Find the average of each category by adding all the grades in one category together, then dividing them by the number of grades there are. For example, if you got a 95, 100, 90, and 85 on your homework, your homework grade would be 91.25 (95+100+90+85 = 365) (365/4 = 91.25). Repeat this for each category.

Multiply your average in a category by the percentage the category is worth. Using the above example, if homework counts for 20 percent of your grade, then 91.25 x .20 = 18.25. Repeat this for each category.

Add together all the categories after multiplying them by what percent of the class they're worth. For example, if your adjusted number for three categories was 18.25, 22, and 40, then your final grade would be 80.25.