How to Solve for Radius in Excel. The radius of a circle or a sphere is the distance between the center and the edge. The radius can be used to calculate a circle's diameter, area and circumference.

The circumference of a circle is its outside edge, and is the same distance from the centre at every point along its length. This distance is called the radius.

Calculate the circumference of the Earth using this equation: Circumference = 360 x distance between your city and the equator / angle of shadow that you measured What value do you get?