# Weighted Average Calculator

The most popular usage of weighted average is used in descriptive statistics, although the calculation is also used in various other areas of math. An extremely common example of the need for using a weighted average calculator is when grades are being calculated.

For a working example, let’s compare the grades of two different classes. Class A, with 3 students, scored the following data set on their most recent exam: [62,75,88]. Class B, with 5 students, scored the following data set on the exact same exam: [65,71,83,84,92].

To obtain the straight average for each class, we would add the test scores and divide by the number of students, for each class. The straight average for Class A is 75. The straight average for Class B is 79. Now, to calculate the straight average of both classes you add the straight average of each individual class together and divide by the total number of classes. In this example, we would take 75 (Class A) + 79 (Class B), which is 152, and divide by 2 (as there are 2 total classes), giving us an overall straight average of 77 for both classes combined.

However, this approach doesn’t account for the difference in the number of students in each class. The value of 77 does not reflect the average student grade independent of class and class size.

To find the weighted average of this data you must weigh the class means by the number of students in each class. To calculate this weighted average you must multiply the number of students in each class by the class average, add the two classes together, and then divide by the total number of students in both classes.

For our example, we would take (3)(75) + (5)(79) / 8, resulting in a weighted average of 77.5.

To use our weighted average calculator, simply enter both of your sets of data, separated by commas with no spaces, such as: 62,75,88 and 65,71,83,84,92.