Work out circle circumference instantly with clear inputs, formula shown and shareable results.
Every circle has the same ratio of circumference to diameter, namely π. So C = πd = 2πr, and the enclosed area is πr².
Circumference
C = 2πr = πd
Area
A = πr²
2π × 5 = 10π ≈ 31.415927 units.
It cannot be written as a ratio of integers; Lambert proved this in 1761, and it is also transcendental.