4.6 Pie chart
A pie chart or circle diagram is used when you want to show a distribution of a few observational values. “Pie pieces” in the chart are called circle sectors.
Here are a few examples from grade statistics from 2004/2005. The table and the diagram shows the grades in junior high (year 9) for the whole of Sweden in mathematics.
The percentage (%) of students who have received a certain grade or who did not reach the goals in mathematics.

Källa: Skolverket 
Drawing a Pie Chart
It’s a good idea if you know about central angles before you read this.
If you draw a pie chart based on a few observational values, you can use the program Excel or some other useful program on your computer. You can even draw a pie chart by using a pen, protractor, and a compass.
We will use the same survey as above, in other words the grade statistics. The table shows the final grades in physical education in elementary school for the whole of Sweden.
Percent (%) students who receive certain grades or who do not reach the goals in the course physical education:

Källa: Skolverket 
If we add the percentages for the different grades, we naturally get
31.6 + 38.4 + 22.9 + 7.1 = 100 %.
You may know that a rotation around a circle is 360 degrees.
We can then say that 360° = 100 %
So 1 % = 3.6°
We then get:
We round off to whole degrees. Draw then a circle with your compass or some round object. Then, it is time to get our your protractor and draw in the different circle sectors. You write then the name and percent in each circle sector.
