# Circumference of a Circle Formula

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Circumference of a circle formula is a formula based on circle radius. This is shown below:-

Circumference of circle = 2 x pi x r

Here pi = 22/7 and r is radius. Generally the unit of radius is m or cm and pi is a constant. Since pi is

constant so there is no unit of pi and 2 is also constant, so the unit of circumference is also m or cm. This

tool describes step by step method to calculate circumference of circle.

This can be understood by the detailed examples, which are shown below:-

Example 1:- Find the Circumference of circle when diameter is 126 cm.

Solution:- Given the diameter of circle, d is 126 cm.

So the radius of circle is (radius is always half of the diameter), r = 126/2 = 126/2 = 63 cm.

Now circumference of circle = 2 x pi x r

Therefore Circumference of circle, C = 2 x 22/7 x 63

So C = 396 cm.

Hence the circumference of circle = 396 cm.

Example 2:- Find the Circumference of circle when diameter is 154 cm.

Solution:- Given the diameter of circle, d is 154 cm.

So the radius of circle is, r = d/2 = 154/2 = 77 cm.

Now circumference of circle = 2 x pi x r

Therefore Circumference of circle, C = 2 x 22/7 x 77

So C = 484 cm.

Hence the circumference of circle = 484 cm.