3 Ways to Calculate Weighted Average - wikiHow Convert the weights into decimals by moving the decimal point 2 places to the left Now you have 0 2, 0 35, and 0 45 These decimals are called weighting factors The next step is to multiply each number by its weighting factor In our example, you would multiply 82 by 0 2, 90 by 0 35, and 76 by 0 45 and get 16 4, 31 5, and 34 2