Circumference of a Circle Formula

P = 2πr

where P stands for perimeter, and r stands for radius .

Circle

The perimeter is the measured distance around the outside of the circle. Think of yourself walking along the black line of the circle above. The perimeter formula would give you the distance you would have to walk if you went all the way around it.

You probably noticed the interchange of the words circumference and perimeter. These are the same when referring to a circle. Sometimes the formula for the circumference uses the Diameter of the circle, which is just twice the radius, so the formulas are exactly the same if you pull out 2r and replace it with d.