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Circle

The circumference, also called perimeter, of a circle is the distance around the edge.
Circle with radius and diameter


The formula for a circle's circumference is:

C=2*r*pi

or

C=d*pi

As you can see, these formulas, especially the one with the diameter d, are very simple. That’s because π actually is defined by the relationship between the circumference and the diameter of a circle.

Calculate area and circumference of a circle

Please enter radius (r) or diameter (d).

Radius (r): 
Diameter (d): 
Pi: