From Wikipedia, the free encyclopedia
Jump to: navigation, search
Gigameter group.png
13 objects with sizes in
the gigametre order of magnitude
Unit information
Unit system metric
Unit of length
Symbol Gm 
Unit conversions
1 Gm in ... ... is equal to ...
   SI units    1×109 m
   astronomical units    0.0066846 AU
 1.0570×10−7 ly
 3.2408×10−8 pc
   imperial/US units    621370 mi
   nautical units    539960 nmi

The gigametre (official spelling used by the International Bureau of Weights and Measures;[1] SI symbol: Gm) or gigameter (American spelling) is a unit of length in the metric system, equal to one billion metres, the SI base unit of length. This is equivalent to 1,000,000 km or approximately 621,370 mi.

Gigametres (from the Greek words gigas = giant[2] and metro = count/measure[3]) are composed exactly of 1,000 megametres. Although fit for distances in astronomy (e.g. a planet's distance from its star) this professional field usually uses the astronomical unit (AU) or millions and billions of kilometres.


See also[edit]


  1. ^ "Definition of the metre". BIPM. Retrieved 26 March 2014. 
  2. ^
  3. ^
  4. ^ Emilio, Marcelo; Kuhn, Jeff R.; Bush, Rock I.; Scholl, Isabelle F. (5 March 2012), Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits, arXiv:1203.4898Freely accessible