Area of a circle from the diameter
The question
cm²
Area of a circle marked 16 cm
How it works.
- 01
The 16 cm marked here goes right across the circle — it is the diameter. The formula needs the radius.
- 02
Half of 16 is 8, so the radius is 8 cm.
- 03
Area is π × r × r. Square the radius first: 8 × 8 = 64.
- 04
Then multiply by π: 64 × 3.14 = 200.96 square cm.