Diameter of a Circle X 3.1416 gives Circumference.

Diameter Squared X .7854 gives Area of Circle.

Diameter Squared X 3.1416 gives Surface of Sphere.

Diameter Cubed X .5236 gives Solidity of Sphere.

One Degree of Circumference X 57.3 gives Radius.

Diameter of Cylinder X 3.1416, and product by its length, gives the Surface.

Diameter Squared X .7854, and product by the length, gives Solid Contents.

A Circular Acre is 235.504 feet, a Circular Rood 117.752 feet, in diameter. The Circumference of the globe is about 24,855 miles, and the Diameter about 7,900 miles. - Whittaker's Almanac.