Circumference is a term used to represent the distance around a circle.
C: Circumference of a circle
r: The length of the radius of a circle
d: The length of the diameter of a circle
π = 3.141 592 653 589 793 238 462 643 383 279 ...
For calculations, pi (π) is usually approximated by using a limited number of digits after the decimal point. To two decimal places, pi is approximately 3.14.