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Circumference of Circle

Circumference of Circle - illustration

The circumference of a circle is a length of an around arc. How to imagine the circumference of a circle? For example, you have a tire and make a point on its edge. After one round move, the point goes a distance which equals to the circumference of a circle.

To calculate the circumference of a circle we need to know its diameter or its radius and the pi number (Ludolph's number). The pi number is a constant and equals to 3.141592... In a circle, the diameter is d = 2 × radius "r". The elementary unit is one metre (1 m).

d=2 × r, also r = d / 2

Circumference of Circle - formula

Circumference of Circle = Ludolph's number × diameter
or
Circumference of Circle = 2 × Ludolph's number × radius

C = π × d = 2 × π × r

Circumference of Circle - calculator

2D & 3D CalcCalculator for Circumference of Circle