Circumference of a circle For any circle with diameter, d, the circumference, C, is found by using the formula C = π d For this circle: C = π d ...

To do this, start by cutting a 3-inch piece of string to serve as the radius of the circle. What’s the radius? It’s half the diameter. Okay, but what’s the diameter?

Written below: d equals C divided by pi., The circumference of a circle is given by the formula 𝑪 = π𝒅. The diameter has been multiplied by π to give the circumference.

The area of this square is AZ squared, or 3.1415258. This differs from the area of the circle by less than 0.0001. Thus, Crockett Johnson approximately squared the circle.

It is derived simply, by dividing the circumference of a circle by its diameter, or π = C/d, but the result is a never-ending "irrational" number: 3.14159265.