Number, called the circumference, that expresses the length of a circle.
The formula to calculate the circumference of a circle is: C = 2πr = πd.
- This circle has a radius of 3 centimetres.
C = 2πr
C ≈ 2 × 3.1416 × 3
C ≈ 18.8496 cm
- The circumference of the Earth is approximately 40 000 km.