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Pie chart can used to compare the relation between the whole and its components. Pie chart is a circular diagram and the area of the sector of a circle is used in pie chart. Circles are drawn with radii proportional to the square root of the quantities because the area of a circle is  .
To construct a pie chart (sector diagram), we draw a circle with radius (square root of the total). The total angle of the circle is  . The angles of each component are calculated by the formula.
Angle of Sector 
These angles are made in the circle by mean of a protractor to show different components. The arrangement of the sectors is usually anti-clock wise.
Example:
The following table gives the details of monthly budget of a family. Represent these figures by a suitable diagram.
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Item of Expenditure
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Family Budget
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Food
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Clothing
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House Rent
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Fuel and Lighting
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Miscellaneous
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Total
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Solution:
The necessary computations are given below:
Angle of Sector 
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Items
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Family Budget
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Expenditure $
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Angle of Sectors
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Cumulative Angle
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Food
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Clothing
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House Rent
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Fuel and Lighting
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Miscellaneous
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Total
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