In Reporting Services, pie chart labeling is optimized to display labels on only several slices of data. Labels may overlap if the pie chart contains too many slices. One solution is to display the labels outside the pie chart, which may create more room for longer data labels. If you find that your labels still overlap, you can create more space for them by enabling 3D. This reduces the diameter of the pie chart, creating more space around the chart.
You can create and modify paginated report definition (.rdl) files in Report Builder and in Report Designer in SQL Server Data Tools. Each authoring environment provides different ways to create, open, and save reports and related items.
To display data point labels inside a pie chart
Add a pie chart to your report. For more information, see Add a Chart to a Report (Report Builder and SSRS).
On the design surface, right-click on the chart and select Show Data Labels.
To display data point labels outside a pie chart
Create a pie chart and display the data labels.
Open the Properties pane.
On the design surface, click on the pie itself to display the Category properties in the Properties pane.
Expand the CustomAttributes node. A list of attributes for the pie chart is displayed.
Set the PieLabelStyle property to Outside.
Set the PieLineColor property to Black. The PieLineColor property defines callout lines for each data point label.
To prevent overlapping labels displayed outside a pie chart
Create a pie chart with external labels.
On the design surface, right-click outside the pie chart but inside the chart borders and select Chart Area Properties.The Chart AreaProperties dialog box appears.
On the 3D Options tab, select Enable 3D.
If you want the chart to have more room for labels but still appear two-dimensional, set the Rotation and Inclination properties to 0.