How to Calculate Pie Chart Angles
Pie charts display the distribution of data with sectors that are sized proportionally to the number of objects in each group. To draw a pie chart accurately, you need to find the angle of each sector in the chart. You can work out the angles for a pie chart following the step by step instructions below, or you can use the convenient pie chart calculator on the left. Simply fill in the blanks in the first column for the number of objects in each group. The calculator will output the percentages and angles in the second and third columns.
For each category you want to represent in the pie chart, determine the number of people/objects or amount of money in each category. For example, suppose a magazines's subscriber list is divided into three non-overlapping categories labeled A, B, and C. Let's say that Category A contains 2347 people, B contains 1209 people, and C contains 894 people.
Add the numbers you found in Step 1 to find the total. Using the example above, we have 2347 + 1209 + 894 = 4450 people.
Divide each category amount by the total, then multiply by 360 to compute the angle measure in degrees. For example numbers above, we have:
A: (2347/4450)(360) = 189.9°
B: (1209/4450)(360) = 97.8°
C: (894/4450)(360) = 72.3°
When you draw the pie chart, the sector for group A will have an angle measure of 189.9°, so it will take up a little more than half of the circle. The sector for group B will measure 97.8°, or a little more than a fourth of the circle. Sector C will have an angle of 72.3°, or about a fifth of the circle.
Short Cut Method
You can also determine the pie chart angle simply by multiplying the percentage by 3.6. For example, sector A takes up 52.74% of the total. Since (52.74)(3.6) = 189.9, this gives you an angle of 189.9°.
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