How to Construct a Circle Graph from Percentages
A circle graph (pie chart) shows how a whole is split into parts. Each slice is a central angle, and the full circle is 360°.
The rule
angle = (percent ÷ 100) × 360°
A shortcut: multiply the percent by 3.6.
Worked example
A monthly budget is 40% rent, 25% food, 20% transport and 15% savings.
| Category | Percent | Angle |
|---|---|---|
| Rent | 40% | 144° |
| Food | 25% | 90° |
| Transport | 20% | 72° |
| Savings | 15% | 54° |
Total: 144 + 90 + 72 + 54 = 360° ✓
Steps to draw it
- Check that the percentages add up to 100%.
- Convert each percent to degrees.
- Draw a circle and a radius as the starting line.
- With a protractor, measure the first angle and draw the next radius. Continue around the circle from the last line.
- Label each slice with its category and percent, and give the graph a title.
Common mistakes
- Angles that do not total 360° because of rounding; adjust the last slice.
- Measuring each angle from the starting line instead of from the previous slice.
- Forgetting to label the slices.