How to Add an Axis Title to an Excel Chart
When you insert a chart in Excel, the program might automatically display a chart title or a legend. In cases where Excel omits these labels or they don't adequately explain the chart, turn on axis titles in Excel 2013's Chart Elements menu or the Layout tab in earlier versions of Excel. Some types of charts, such as pie charts, cannot use axis titles and do not display the option. Switch to another chart style, such as a line, scatter or bar chart to add the titles.
Select a chart and click the Chart Elements "+" icon to its right.
Check "Axis Titles" to add titles to all axes on the chart, or open the drop-down menu next to "Axis Titles" and pick a single axis to label.
Click an axis title and begin typing to write a label by hand. To link an axis title to an existing cell, select the title, click in the formula bar, type an "=" and then click the cell. Press "Enter" to set the title. To change the title's text later, edit the text in the linked cell rather than on the chart.
Excel 2010 or 2007
Select a chart, switch to the "Layout" tab and press the "Axis Titles" button in the Labels section.
Choose the axis you want to title and pick an orientation for the label. Choose "Rotated Title" for a vertical axis to mimic the default style in Excel 2013.
Type a title's text box to write a label. To tie a title to a cell's contents, select the title, type an "=" in the formula bar, click the cell and press "Enter." Edit a linked cell to update the title on the chart.