How to add a horizontal average line to chart in Excel?

If you want to insert a horizontal average line to a chart, you can calculate the average of the data first, and then create the chart. Please do as this:

1. Calculate the average of the data with Average function, for example, in Average Column C2, type this formula: =Average($B$2:$B$8), and then drag this cell's AutoFill handle to the range as you need. See screenshot:

2. And then select this range and choose one chart format that you want to insert, such as 2-D Column under the Insert tab. See screenshot:

3. And a chart has been created, please click one of the average data column (the red bar) in the chart, right click and select the Change Series Chart Type from the context menu. See screenshot:

4. In the popped out Change Chart Type dialog, click to highlight the Combo in the left bar, click box behind the Average, and then select the a line chart style from the drop down list. See screenshot:

5. Click the OK button. Now, you have a horizontal line representing the average in your chart, see screenshot:

This method will recommend an amazing tool, Add Line to Chart feature of Kutools for Excel, to quickly add a horizontal average line to the selected column chart with 2 clicks only!

Supposing you have created a column chart as below screenshot shown, and you can add a horizontal average line for it as follows:

1. Select the column chart, and click Kutools > Charts > Add Line to Chart to enable this feature.

2. In the Add line to chart dialog, please check the Average option, and click the Ok button.

Now the horizontal average line is added to the selected column chart at once.

Supposing you have created a column chart with your data in your worksheet, and the following VBA code also can help you to insert an average line across your chart.

1．Click one of the data column in your chart, and then all the data columns will be selected, see screenshot:

2. Hold down the ALT + F11 keys, and it opens the Microsoft Visual Basic for Applications window.

3. Click Insert > Module, and paste the following code in the Module Window.

VBA: add an average line to the chart

Sub AverageLine()
'Update 20130907
Dim ser As Series
Dim arr As Variant
Dim total As Double
Dim outArr As Variant
If VBA.TypeName(Application.Selection) <> "Series" Then Exit Sub
Set ser = Application.Selection
arr = ser.Values
total = Application.WorksheetFunction.Average(arr)
ReDim outArr(LBound(arr) To UBound(arr))
For i = LBound(outArr) To UBound(outArr)
    outArr(i) = total
Next
With ActiveChart.SeriesCollection.NewSeries
    .XValues = ser.XValues
    .Values = outArr
    .Name = "Average " & ser.Name
    .AxisGroup = ser.AxisGroup
    .MarkerStyle = xlNone
    .Border.Color = ser.Border.Color
    .ChartType = xlLine
    .Format.Line.ForeColor.ObjectThemeColor = msoThemeColorAccent6
End With
End Sub

4. Then press F5 key to run this code, and a horizontal average line has been inserted into the column chart. See screenshot:

Note: This VBA only can run when the Column format you insert is 2-D Column.