Pie Chart

Divide the number of responses for that category by the total number of responses, then multiply by 360 degrees. For example, 25 basketball responses out of 100 gives 25 ÷ 100 × 360 = 90 degrees. Repeat this for every category in your frequency table.

A pie chart fills a complete circle, and a complete circle measures 360 degrees. Once you have worked out every central angle, adding them together should give exactly 360 degrees. If your total is different, check your calculations again before you start drawing.

Use the formula: count equals the central angle divided by 360 degrees, multiplied by the total count. For a ham slice of 36 degrees with 80 students surveyed, 36 ÷ 360 × 80 gives 8 students. The same method works for any category once you know the total.

Subtract all the known central angles from 360 degrees, and the result is the missing slice's angle. This works because every slice in a pie chart adds up to 360 degrees. In the pizza example, subtracting the other angles leaves 72 degrees for the pineapple slice.

Divide the central angle by 360 degrees. For instance, a pineapple slice of 72 degrees gives 72 ÷ 360 = 20%, so 20% of the group prefers pineapple. This turns any slice angle into the percentage of the total that the category represents.

You use a pie chart to compare the categories that make up a whole. Because each slice shows a category's share of the total, a pie chart makes it easy to see at a glance which parts take up larger or smaller proportions.