When we want to calculate the average of a set of values with different levels of relevance, we compute for the weighted average. Excel allows us to calculate the weighted average using the SUMPRODUCT and SUM functions.
Figure 1. Final result: Calculate the weighted average
Syntax of the SUMPRODUCT Function
SUMPRODUCT returns the sum of the products of two or more components in the given arrays.
=SUMPRODUCT(array1, [array2], [array3], ...)
- array – a range of values or cells whose values we want to multiply with other values and then add
- All array arguments must be in the same size
- Non-numeric values in an array are treated as zeros
Syntax of SUM Function
SUM adds all given values
- number1 – any number, array or cell reference whose values we want to add
- Only number1 is required; succeeding numbers are optional
Setting up the Data
Our table consists of three columns: Measures (column B), Rating (column C) and Weight (column D). In cell F3, we will calculate the weighted average of the ratings.
Figure 2. Sample data to calculate the weighted average
Calculate the weighted average of the ratings
In order to calculate the weighted average of the ratings, we follow these steps:
Step 1. Select cell F3
Step 2. Enter the formula:
Step 3. Press Enter
The SUMPRODUCT returns the sum of the products of the ratings and weights (rating x weight). Actual calculation of the SUMPRODUCT looks like this:
=(C3xD3) + (C4xD4) + (C5xD5)
The SUM function returns the total of the weights.
The SUMPRODUCT divided by the SUM function returns the value of the weighted average of the ratings. As a result, the value in cell F3 is 90.70%.
Figure 3. Using SUMPRODUCT and SUM to calculate weighted average
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