Circumference formula

The circumference of a circle is the distance around it. The formula to calculate circumference is C = 2πr, where C is the circumference, π (pi) is approximately 3.14, and r is the radius (the distance from the center of the circle to its edge). Alternatively, you can use the diameter (the distance across the circle through its center) in the formula C = πd, where d is the diameter. This means knowing just the radius or diameter allows you to easily find how far it is around the circle.