This tutorial shows you how to quickly calculate simple moving averages in Excel, using functions to determine moving averages over the last N days, weeks, months, or years, and how to add a moving average trendline to your charts.

Previous articles covered calculating standard and weighted averages in Excel. This tutorial explains two methods for calculating moving averages.

What is a Moving Average?

A moving average (also called a rolling average, running average, or moving mean) is a series of averages calculated across subsets of a dataset. It's used in statistics, economic forecasting, and weather prediction to identify underlying trends. In finance, it indicates a security's average value over a specific period. Businesses often use moving averages of sales (e.g., the last three months) to track recent trends.

For example, a three-month moving average of temperatures would average January-March temperatures, then February-April, March-May, and so on. Several types of moving averages exist (simple, exponential, variable, triangular, weighted), but this tutorial focuses on the common simple moving average.

Calculating Simple Moving Averages in Excel

Two methods exist: using formulas and trendlines.

Calculating Moving Averages for a Specific Time Period

The AVERAGE function easily calculates simple moving averages. If column B contains average monthly temperatures, and you need a three-month moving average (as in the image above):

In the cell corresponding to the third month (C4 in the example), enter: =AVERAGE(B2:B4)

Copy this formula down. Use relative row references (without $) for proper adjustment. You can verify the result using the SUM function: =SUM(B2:B4)/3

Calculating Moving Averages for the Last N Days/Weeks/Months/Years

For data like sales or stock quotes, where you want the average of the last three months at any time, you need a formula that recalculates with each new month's entry. Combine AVERAGE with OFFSET and COUNT:

=AVERAGE(OFFSET(*first cell*, COUNT(*entire range*)-*N*,0,*N*,1))

Where N is the number of periods (days, weeks, months, years).

Example: If data is in column B starting at row 2, and you want the last three months' average:

=AVERAGE(OFFSET(B2,COUNT(B2:B100)-3,0,3,1))

Explanation:

• COUNT(B2:B100) counts entries in column B.
• OFFSET starts at B2, moves up COUNT(B2:B100)-3 rows, creating a range of 3 rows and 1 column (the last three months).
• AVERAGE calculates the average of this range.

Tip: Use a large range in COUNT (like B2:B100) to accommodate future data additions.

Calculating Moving Averages for the Last N Values in a Row

To calculate a moving average for the last N values in a row, adjust the OFFSET formula:

=AVERAGE(OFFSET(*first cell*,0,COUNT(*range*)*-N*,1,*N*))

Example: If B2 is the first cell, and you want the average of the last three numbers in the row:

=AVERAGE(OFFSET(B2,0,COUNT(B2:N2)-3,1,3))

Creating a Moving Average Chart in Excel

Adding a moving average trendline to an existing chart is simple using Excel's Trendline feature.

1. Select the chart. In Excel 2013, go to Design > Add Chart Element > Trendline > More Trendline Options…. In Excel 2010/2007, go to Layout > Trendline > More Trendline Options. For a quick result without detailed settings, click Moving Average.

2. The Format Trendline pane (Excel 2013) or dialog box (Excel 2010/2007) appears. Select Moving Average and specify the period (interval).

3. The trendline is added to your chart.

Customize the line style using the Fill & Line or Effects tabs. Add multiple trendlines with different periods for a comprehensive analysis.

This tutorial covers calculating moving averages in Excel. A sample workbook is available for download.

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