Pie Diagrams | Meaning, Example and Steps to Construct

What is Pie Chart or Pie Diagram?

A circle can be divided into parts to show the ratios of different components. A pie diagram is one such representation. Pie charts are also referred to as Angular Circle Diagrams. The circle is divided into as many sections as there are elements by drawing straight lines from the centre to the circumference. According to Herbert and Raymond, a pie diagram is a circular diagram divided into smaller sections. The section size of a pie diagram represents the proportion of each part to the whole. 

While preparing a pie diagram, different sectors which represent different component elements should be identified from one another through varied shades, and colours, or by using either expressive or descriptive labels. 

Steps to Construct a Pie Diagram

To construct a pie diagram, the following steps should be followed:

1. Using a compass, draw a circle according to the size of the paper and the data to be represented.
2. Calculate the percentages of the total from the values of the various components.
3. No convert the percentage values into corresponding degrees. Since one circle comprises 360° and the percentage values of all of the components’ is equal to 100, the 1% value is represented by   or 3.6°. Therefore, to determine the size of the angles of each component, multiply the percentage values by 3.6.
4. Use a radius (preferably horizontally) as a baseline for drawing the angles represented by the first component. The new line drawn will serve as a base for the angular representation of the second component. Repeat this process until each component is represented in the circle.
5. Now represent the different components with different colours, designs, or shades to properly represent the pie diagram.

Example of Pie Diagram:

Draw a pie chart to reflect the following expenditure for an ordinary working-class family.

Items	% of Total Expenditure
Food	45
Clothing	15
Education	25
Electricity	10
Miscellaneous	5

Solution:

The sum of the percentages of total expenditure is 100. It means that the total angle; i.e., 360° represents 100. Now, multiply each of the percentages by  or 3.6° to determine the proportionate angles.

Items	% of Total Expenditure	Proportionate Angles
Food	45%	45 x 3.6  = 162°
Clothing	15%	15 x 3.6  = 54°
Education	25%	25 x 3.6  = 90°
Electricity	10%	10 x 3.6  = 36°
Miscellaneous	5%	5 x 3.6  = 18°
	100%	360°

According to the degrees of angles at the centre, the circle is divided into five parts. Hence, the pie diagram for the given data will be represented as: