distance circumference
Circumference of a circle[edit] Circle illustration with circumference (C) in black, diameter (D) in cyan, radius (R) in red, and centre or origin (O) in magenta. Circumference = Ï Ã diameter = 2 Ã Ï Ã radius. The circumference of a circle is the distance around it. The term is used when measuring physical objects, as well as when considering abstract geometric forms. When a circle's diameter is 1, its circumference is Ï. When a circle's radius is 1âcalled a unit circleâits circumference is 2Ï.