What is the formula for circumference of a circl?

The circumference of a circle is the length around it. The circumference of a circle can be calculated from its diameter using the formula: Circumference of a circle = 2*pi*radius or

Circumference of a circle = pi*diameter

where r is the radius and d is the diameter of the circle, and � (the Greek letter pi) is defined as the ratio of the circumference of the circle to its diameter.

(the numerical value of pi is 3.141 592 654 589 793...).
d * pi

or 2 * r * pi

Where d is diameter and r is radius and pi = 3.14159