Figure your average for each assignment or category by dividing your points earned by the total possible points. For example, if you earned a 40 out of 50 on your homework, divide 40 by 50 to get 0.8. If on your three projects for the term, you received 20 out of 25, 40 out of 45 and 28 out of 30, you earned 70 out of 100 points, so divide 70 by 100 to get 0.7.
Multiply the category average by the weight factor for each category. For example, if your final exam equals 45 percent of your grade, multiply 45 by 0.8 to get 36. If projects are 35 percent of your grade, multiply 35 by 0.7 to get 24.5.
Add the products of each category times the weight factor to find the final mark. For example, if you have 36 from your final, 24.5 from your projects and 19 for homework, add 36 plus 24.5 plus 19 to find your mark for the class equals 79.5.