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Measurement units: solid angle
Symbol: sr
multiplesSteradian (sr): multiples and submultiples
Square degrees to steradians Steradians to square degrees

info symbol: sr

The steradian or square radian is the unit of solid angle in the International System of Units (SI).

It is used in three-dimensional geometry, and is analogous to the radian, which quantifies planar angles.

A steradian can be defined as the solid angle subtended at the centre of a unit sphere by a circular unit area on its surface.

The solid angle is related to the area it cuts out of a sphere:

Ω = (A / r2) * sr

Ω is the solid angle
A is the surface area of the spherical cap
r is the radius of the sphere

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  • 1 steradian sr = 1*3282.806350011 square degrees deg²
  • 1 steradian sr = 1*1000000.000000000 microsteradian μsr
  • 1 steradian sr = 1*100.000000000 centisteradians csr
  • 1 steradian sr = 1*1000.000000000 millisteradian msr
  • 1 steradian sr = 1*10.000000000 decisteradians dsr