Square degree

A square degree (deg2) is a non-SI unit measure of solid angle.

Other denotations include sq.

Just as degrees are used to measure parts of a circle, square degrees are used to measure parts of a sphere.

Analogous to one degree being equal to ⁠π/180⁠ radians, a square degree is equal to (⁠π/180⁠)2 steradians (sr), or about ⁠1/3283⁠ sr or about 3.046×10−4 sr.

The whole sphere has a solid angle of 4πsr which is approximately 41253 deg2: