Metre - SI Prefixed Forms of Metre

SI Prefixed Forms of Metre

SI prefixes are often employed to denote decimal multiples and submultiples of the metre, as shown in the table below. As indicated in the table, some are commonly used, while others are not. Long distances are usually expressed in km, astronomical units (149.6 Gm), light-years (10 Pm), or parsecs (31 Pm), rather than in Mm, Gm, Tm, Pm, Em, Zm or Ym; "30 cm", "30 m", and "300 m" are more common than "3 dm", "3 dam", and "3 hm", respectively.

The term micron is often used instead of micrometre, but this practice is officially discouraged.


SI multiples for metre (m)
Submultiples Multiples
Value Symbol Name Value Symbol Name
10−1 m dm decimetre 101 m dam decametre
10−2 m cm centimetre 102 m hm hectometre
10−3 m mm millimetre 103 m km kilometre
10−6 m µm micrometre 106 m Mm megametre
10−9 m nm nanometre 109 m Gm gigametre
10−12 m pm picometre 1012 m Tm terametre
10−15 m fm femtometre 1015 m Pm petametre
10−18 m am attometre 1018 m Em exametre
10−21 m zm zeptometre 1021 m Zm zettametre
10−24 m ym yoctometre 1024 m Ym yottametre
Common prefixed units are in bold face.

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