Multiply each score by its corresponding weight. Using GPA as an example, if you made a 4.0 in a two-credit course, a 3.0 in a three-credit course and a 2.0 in a four-credit course, the products would be 8.0, 9.0 and 8.0, respectively.
Add each of these products. In the example, the result is 25.0.
Add the total weights. In the example, this is 9 credits.
Divide the total score by the total weight to calculate your weighted score. In the example, 25.0 divided by 9 equates to a 2.78 GPA. If this were a simple average, you would have a 3.0, but the greater weight of the four credit course dropped your weighted score.
Convert each percentage weight into decimal format by dividing by 100. As an example, if you had two regular tests that each accounted for 25 percent of your grade and one final exam which counted 50 percent, they would be converted to 0.25, 0.25 and 0.50, respectively.
Multiply each score by its respective weight. If in the example you scored 80 and 90 on your regular tests, but got a 70 on the final due to late night partying, the products would be 20, 22.5 and 35, respectively.
Add each total to compute your weighted score. In the example, you would have 77.5, which rounds to 78. If this were a simple average, you would have an 80, but the final's greater weight dropped your weighted score.