We can use a formula that combines the SUMPRODUCT function and the SUM function to calculate the weighted average of a set of values in a range. The steps below will walk through the process.
Figure 1- Final result of the Weighted Average
General Formula
=SUMPRODUCT(values,weights)/SUM(weights)
- Values: These are the numbers in the data
- Weights: This is the percentage weight of each number in the data
Formula
=SUMPRODUCT(B4:B11,C4:C11)/SUM(C4:C11)
Setting up the Data
We will calculate the weighted average score of the courses in the data below.
- Column A, B, and C will contain the Course, Score, and Weight respectively
- The mean or normal average score for the courses will be returned in Cell E7. The weighted average will be returned in Cell E4
Figure 2 – Setting up the Data
Weighted Average
- We will click on Cell E4
- We will insert the formula below into Cell E4
=SUMPRODUCT(B4:B11,C4:C11)/SUM(C4:C11) - We will press the enter key
Figure 3- Weighted Average Score for the Courses
Normal Average
- We will click on Cell E7
- We will insert the formula below into Cell E7
=AVERAGE(B4:B11) - We will press the enter key
Figure 4- Average Score for the Courses
Explanation
The SUMPRODUCT function multiplies the cells in Column B with cells of Column C (B4*C4 and so on) and returns the sum of each multiplied cells. This sum is then divided by the sum of the scores that have been added by the SUM function.
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