Pie Charts

The most common customizations to <apex:pieSeries> charts is to colors and labels. Use the colorSet attribute and the <apex:chartLabel> component that were demonstrated in previous examples.
To create a ring chart instead of a pie chart, set the donut attribute. The donut attribute is an integer between 0 and 100 and represents the percentage of the radius of the hole. Here’s a simple ring chart:
Ring Chart
<apex:chart data="{!pieData}" height="400" width="500" background="#F5F5F5">
    <apex:legend position="left"/>
    <apex:pieSeries labelField="name" dataField="data1" donut="50">
        <apex:chartLabel display="middle" orientation="vertical" 
            font="bold 18px Helvetica"/>
    </apex:pieSeries>
</apex:chart>