Add a trendline

1. Select a chart.

2. Select the + to the top right of the chart.

3. Select Trendline.

   Note: Excel displays the Trendline option only if you select a chart that has more than one data series without selecting a data series.

4. In the Add Trendline dialog box, select any data series options you want, and click OK.

Format a trendline

1. Click anywhere in the chart.

2. On the Format tab, in the Current Selection group, select the trendline option in the dropdown list.

3. Click Format Selection.

4. In the Format Trendline pane, select a Trendline Option to choose the trendline you want for your chart. Formatting a trendline is a statistical way to measure data:
   

5. Set a value in the Forward and Backward fields to project your data into the future.

Add a moving average line

You can format your trendline to a moving average line.

1. Click anywhere in the chart.

2. On the Format tab, in the Current Selection group, select the trendline option in the dropdown list.

3. Click Format Selection.

4. In the Format Trendline pane, under Trendline Options, select Moving Average. Specify the points if necessary.

   Note: The number of points in a moving average trendline equals the total number of points in the series less the number that you specify for the period.

Add a trend or moving average line to a chart in Office 2010