Steradian

A unit of solid-angle measure in the International System of Units (SI). The steradian is defined as the solid angle of a sphere subtended by a portion of the surface whose area is equal to the square of the sphere's radius.

Steradian

A unit of solid-angle measure in the International System of Units (SI).

The steradian is a unit of solid-angle measure in the International System of Units (SI). It is defined as:

The solid angle of a sphere subtended by a portion of the surface whose area is equal to the square of the sphere's radius.

The complete surface area of a sphere is 4π times the square of its radius and:

The total solid angle about a point is equal to 4π steradians.

Calculator

Inputs

Surface Area (m²)

Radius of Sphere (m)

Results

Solid Angle-- sr

Total Solid Angle (4π)-- sr

Sphere Radius (m)	Surface Area (m²)	Solid Angle (sr)
1	4π ≈ 12.57	4π ≈ 12.57
2	16π ≈ 50.27	4π ≈ 12.57
5	100π ≈ 314.16	4π ≈ 12.57
10	400π ≈ 1256.64	4π ≈ 12.57