Excel: How to Calculate 3-Month Moving Average

In time series analysis, a 3-month moving average is simply the average value of the 3 months leading up to and including a certain month.

The following example shows how to calculate a 3-month moving average for a dataset in Excel.

Example: Calculate 3-Month Moving Average in Excel

Suppose we have the following dataset that shows the total sales made during 12 consecutive months by some company:

To calculate the 3-month moving average of the sales values, we can type the following formula into cell C4:

=AVERAGE(B2:B4)

We can then click and drag this formula down to each remaining cell in column C:

The values in column C represent the 3-month moving average of the values in the sales column.

For example, the 3-month moving average of sales in March is 25.667.

We can confirm this is correct by manually calculating the average of sales for the three months leading up to and including this month:

3-Month Moving Avg. of Sales in March: (22+25+30) / 3 = 25.667

This matches the value calculated by our formula.

Since we clicked and dragged this formula down to each cell in column C, the formula automatically updated to use the most recent 3 months to calculate each 3-month moving average.

For example, cell C13 uses the range C11:C13 to calculate its 3-month moving average:

Note: We had to type our formula starting in cell C4 because this represented the first date that had 3 months to use for calculating the 3-month moving average.