How to calculate a pie chart

A pie chart is a visual way to represent information. Although you can use fractions or percentages alone to represent the same data, many people find that having a picture makes it easier to see proportions. The best thing about a pie chart is that it can work for both visual and text-oriented people. The individual slices can each have their percentage value included, along with the picture.

Add up the total from all the data you are collecting. For example, if you're making a pie chart of the number of students in school by grade, you would add up the freshmen, sophomores, juniors and seniors to get the total number of students.

Divide each component by the total sum. For example, if there are 250 freshmen out of a student population of 750, divide 250 by 750 to get 0.333. Record all the totals to at least the thousandths place.

Multiply the decimals from step 3 by 360° degrees to get the number of degrees of each pies slice. Round the number to the nearest degree. For example, 0.333 x 360 = 120, so the freshman slice in the pie chart takes up 120° degrees.

Draw a circle. You can use a stencil, or retrace one with a compass. Put a dot in the exact middle of the circle.

Draw one straight line from the centre to one of the edges of the circle.

Measure out the first slice of the pie with a protractor. For example, for the freshman slice you would measure 120° degrees from the first line and put a dot on the outside of the circle at the point corresponding to that angle.

Draw a second line from the centre of the circle at the angle you just measured. Repeat steps 6 and 7 until the whole circle is divided up and all the slices are represented.

Label each slice of the circle. Put in what it represents and the percentage. To get a percentage, multiply the decimal from step 3 by 100. In our example, you would label the first slice of the pie as "Freshman, 33.3%".

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