Square degree

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Physical unit
Unit name Square degree
Unit symbol , ,
Physical quantity (s) Solid angle
Formula symbol
In SI units

Square degrees ( deg² , (°) ² ) ( English square degree or sq degree ) is a (non-legal) unit for the solid angle . It is mainly used in astronomy as a measure of the extent of an object in the sky .

The sub-units are called accordingly:

  • Square arc minute ( English square arcmin )  square degrees
  • Square arcsecond ( English square arcsec )  square minute  square degrees.

The full solid angle of the celestial sphere is sr =

The size of a celestial object in square degrees results from the proportion of the celestial sphere that the object covers, multiplied by 41253.

The conversion of a square degree into steradian results in:


For small angles , solid angles can be calculated approximately as with surfaces: an object whose extension measures 1 degree in one direction and 1 degree perpendicular to it, therefore covers a solid angle of around 1 square degree.

See also