A good way to use a pie chart is when you want to show relative proportions to a whole. A pie chart should use between two and six data points- too many slices may make it difficult to interpret. It can only display data that belongs to one data series, and each of its values must be positive.
Types of pie charts
Standard Pie Chart
This is standard- the most popular pie chart. You will probably use this chart most often.
3-D Pie Chart
This pie chart is shown with the appropriate perspective. When you use the 3-D Pie Chart you will get access to additional tools, such as 3-D rotation and Perspective, which is not available in the standard 2-D chart.
Pie of Pie Chart
When a pie chart has many small parts, you may want to display them on a second pie chart, which is a slice of the first one.
Bar of Pie Chart
Bar of Pie chart is similar to the Pie of Pie chart. The difference is that the selected slices are displayed on the Bar chart instead.
If you have more than one data series you can use this type of chart.
When you have more than one data series it is recommended to use other charts, instead of the doughnut chart, because it's hard to see proportions between elements in a different series.