The Jupiter radius or Jovian radius (plural Jupiter radii or Jovian radii; denoted as RJ or, less commonly, RJup) has a value of 71,492 km (44,423 mi), or of 11.2 Earth radii (R🜨) (one Earth radius, 6378 km, equals 0.08921 RJ). The Jupiter radius is a unit of length used in astronomy to describe the radii of large planets (especially gas giants) and certain exoplanets. It is also used in describing certain stars, in particular brown dwarfs.
The general shape of the planet Jupiter has been directly measured from radio occultations of passing spacecraft, starting with the Pioneer and Voyager missions. This method gives an overall margin of error of about ±5 km. Estimates of the radius at one bar pressure are then determined through extrapolation. The planet Jupiter has the approximate shape of an oblate spheroid, which is mainly set by the rate of rotation. This gives a difference of about 10% between its polar and equatorial radii. The polar radius has been determined with an accuracy of ±10 km (as of 1987). Density fluctuations within the planet can create variations in the equatorial radius of up to 30 km. The winds in Jupiter's outer atmosphere can vary the radius by up to 4 km.