What is a pie chart?
A pie chart is a circle split into slices called sectors. Each sector shows one part of the whole. A bigger slice means a bigger share, and all the slices together make one full circle.
Key idea
A full circle is 360° and stands for 100% (the whole group). Half the circle is 180° or 50%, and a quarter is 90° or 25%.
Reading a slice
To find how many items a slice stands for, first work out its fraction of the whole, then multiply by the total number in the group. You can turn a percentage into a fraction, or divide the sector's angle by 360° to get the same fraction.
Worked example
60 pupils name their favourite drink. The “juice” sector is ¼ of the pie. How many chose juice?
Juice = ¼ × 60 = 15 pupils.
If “milk” fills 90°, that is 90 ÷ 360 = ¼ of the pie, so 15 pupils too.
Remember
- All sectors add up to 360° and to 100%.
- Bigger sector = bigger share.
- Change to a fraction first, then multiply by the total.