How to change the size of the doughnut hole in ASP.NET WebForms Chart?

You can customize the size of doughnut hole and the doughnut by using DoughnutCoefficient property and DoughnutSize property respectively with respect to chart size.

Doughnut Size

Doughnut series supports DoughnutSize property that controls the size of the doughnut series with respect to the available size. Doughnut series takes the entire chart space when DoughnutSize is 1, it takes value from 0 to 1. By default the value of doughnutSize is 0.8

ASP

 <ej:Chart ID="container" runat="server">        
        . . . . . .
       <Series>
           <ej:Series DoughnutSize="0.7">               
                      . . . . . . .
                      . . . . . . .
           </ej:Series>
       </Series>
       . . . . . .  
</ej:Chart>

The following screenshot displays doughnut chart with doughnut size 0.7

Doughnut Coefficient

Doughnut charts are pie charts with a hole at center, whose value is specified using DoughnutCoefficient property. It takes values from 0 to1. By default the value of DoughnutCoefficient is 0.4

ASP

<ej:Chart ID="container" runat="server">        
        . . . . . . 
        . . . . . .
       <Series>
           <ej:Series DoughnutCoefficient="0.6">
                      . . . . . . .
                      . . . . . . .        
           </ej:Series>
       </Series>
</ej:Chart>

The following screenshot displays doughnut chart with doughnut coefficient 0.6