How to Use a Protractor to Create a Circle Graph

Written by mike gamble
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How to Use a Protractor to Create a Circle Graph
Circle graphs show relative proportions of data at a glance. (Thinkstock/Comstock/Getty Images)

A circle graph makes it easy to see at a glance how the parts of some subject matter are related to the whole. This type of graph is also commonly known as a pie chart, because each sector of the graph resembles a piece of pie. The size of each piece indicates how much an item contributes to the whole. Each sector is also commonly filled in with a distinct colour and labelled with a description and percentage. Because they're so easy to read, circle graphs are currently the most common way to represent data.

Skill level:
Easy

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Things you need

  • Compass
  • Poster board
  • Ruler

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Instructions

  1. 1

    Make a table listing all the elements that make up the whole. On the left side of the table put the labels or names for each of the items and on the right side list the percentage that each item contributes to the whole.

  2. 2

    Add up the percentages to verify that the total is 100 per cent. If your total comes up short, double-check to make sure you included everything and that your math is correct.

  3. 3

    Convert each of the percentages to a decimal and multiply by 360 degrees. List these values to the right of the percentages as a new column in your table. For example, your table may show that eating takes up 15 per cent of your day. Convert 15 per cent to a decimal and multiply by 360 degrees: 0.15 x 360 degrees = 54 degrees.

  4. 4

    Draw a large circle with a compass on a piece of poster board. Use a ruler to draw a vertical line from the centre of the circle to the circle's circumference.

  5. 5

    Lay the protractor on the poster board with the centre of the protractor over the centre of your graph. Rotate the protractor so that the 90 degree mark is to the right and the protractor is lined up with the vertical line you just drew.

  6. 6

    Select the largest value from the degrees column of your table and make a small mark where that angle is indicated on the protractor. Draw another line from the centre of your graph through the mark you just made, extending it to the circle's circumference.

  7. 7

    Continue marking out your lines, each time selecting the next largest value from the degrees column and using the last line you drew as the starting point for your angle.

Tips and warnings

  • Use a marker and compass to make the circumference of your graph stand out. With your ruler, you can do the same to emphasise each sector's lines. Colour each sector with a different colour marker to make your graph easier to read.

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