Draw a circle on a map
The radius of a cylindrical shape is also called the radius. The radius is the measured distance from any point on the edge of a circle (or sphere or cylinder) to the centre.
Since a diameter is the distance between two extreme points of a circle, the radius is half the diameter. To calculate the circumference of a sphere or circle, you need the radius. There are two ways to calculate the circumference: The circumference of a circle is pi x the diameter. The circumference of a circle is 2 x radius x pi.