The **steradian** (symbol: **sr**) is the SI unit of solid angle. It is used to quantify two-dimensional angular spans in three-dimensional space, analogously to how the radian quantifies angles in a plane. The name is derived from the Greek *stereos* for "solid" and the Latin *radius* for "ray, beam".

The steradian, like the radian, is dimensionless, essentially because a solid angle is the ratio between the area subtended and the square of its distance from the vertex: both the numerator and denominator of this ratio have dimension length2. It is useful, however, to distinguish between dimensionless quantities of different nature, so in practice the symbol "sr" is used to indicate a solid angle. For example, radiant intensity can be measured in watts per steradian (W·sr−1). The steradian was formerly an SI supplementary unit, but this category was abolished from the SI in 1995 and the steradian is now considered an SI derived unit.

Read more about Steradian: Definition, Other Properties, Analogue To Radians, SI Multiples

### Other articles related to "steradian, steradians":

... Radiant intensity Ie watt per

**steradian**W⋅sr−1 M⋅L2⋅T−3 power per unit solid angle ... Spectral intensity Ieλ watt per

**steradian**per metre W⋅sr−1⋅m−1 M⋅L⋅T−3 radiant intensity per wavelength ... Radiance Le watt per

**steradian**per square metre W⋅sr−1⋅m−2 M⋅T−3 power per unit solid angle per unit projected source area ...

**Steradian**- SI Multiples

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**Steradians**only go up to 4π ≈ 12.56637, so the large multiples are not usable for the base unit, but could show up in such things as rate of coverage of solid angle, for example ... plus liquid water on Earth, relative to Earth (cyan on map) 100

**steradian**sr Area of Oceania plus Asia excluding Russia, relative to Earth (yellow ...

... Radiant intensity Ie watt per

**steradian**W⋅sr−1 M⋅L2⋅T−3 power per unit solid angle ... Spectral intensity Ieλ watt per

**steradian**per metre W⋅sr−1⋅m−1 M⋅L⋅T−3 radiant intensity per wavelength ... Radiance Le watt per

**steradian**per square metre W⋅sr−1⋅m−2 M⋅T−3 power per unit solid angle per unit projected source area ...

... Radiant intensity Ie watt per

**steradian**W⋅sr−1 M⋅L2⋅T−3 power per unit solid angle ... Spectral intensity Ieλ watt per

**steradian**per metre W⋅sr−1⋅m−1 M⋅L⋅T−3 radiant intensity per wavelength ... Radiance Le watt per

**steradian**per square metre W⋅sr−1⋅m−2 M⋅T−3 power per unit solid angle per unit projected source area ...

... Radiant intensity Ie watt per

**steradian**W⋅sr−1 M⋅L2⋅T−3 power per unit solid angle ... Spectral intensity Ieλ watt per

**steradian**per metre W⋅sr−1⋅m−1 M⋅L⋅T−3 radiant intensity per wavelength ... Radiance Le watt per

**steradian**per square metre W⋅sr−1⋅m−2 M⋅T−3 power per unit solid angle per unit projected source area ...