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This is a list of units that are not defined as part of the International System of Units (SI), but are otherwise mentioned in the SI,[1] because either the General Conference on Weights and Measures (CGPM) accepts their use as being multiples or submultiples of SI-units, they have important contemporary application worldwide, or are otherwise commonly encountered worldwide.

Units officially accepted for use with the SIEdit

Name Symbol Quantity Value in SI units
minute min time (SI unit multiple) 1 min = 60 s
hour h time (SI unit multiple) 1 h = 60 min = 3600 s
day d time (SI unit multiple) 1 d = 24 h = 1440 min = 86400 s
astronomical unit au length (SI unit multiple) 1 au = 149597870700 m
degree ° plane angle (dimensionless unit) 1° = (π / 180) rad
minute plane angle (dimensionless unit) 1′ = (1 / 60)° = (π / 10800) rad
second plane angle (dimensionless unit) 1″ = (1 / 60)′ = (1 / 3600)° = (π / 648000) rad
hectare ha area (SI unit decimal multiple) 1 ha = 1 hm2 = 10000 m2
litre l or L volume (SI unit decimal submultiple) 1 L = 1 dm3 = 1000 cm3 = 0.001 m3
tonne t mass (SI unit decimal multiple) 1 t = 103 kg
dalton Da mass 1 Da = 1.66053906660(50)×10−27 kg[2][3]
electronvolt eV energy 1 eV = 1.602176634×10−19 J
neper Np level of a field quantity LF = ln(F / F0) Np
    level of a power quantity LP = 1/2 ln(P / P0) Np
bel, decibel B level of a field quantity LF = 2 log10(F / F0) B
    level of a power quantity LP = log10(P / P0) B

Common units not officially sanctionedEdit

The following table lists units mentioned in side- and footnotes in the 9th SI brochure. Units that occur in historical material recorded in the appendices are not included.

Name Symbol Quantity Equivalent SI unit
gal[4] Gal acceleration 1 Gal = 1 cm/s2 = 0.01 m/s2
unified atomic mass unit[5] u mass 1 u = 1 Da = 1.66053906660(50)×10−27 kg[2]
volt-ampere reactive var reactive power 1 var = 1 V⋅A

See alsoEdit

ReferencesEdit

  1. ^ "SI brochure (9th edition)". BIPM. 2019. §4 Non-SI units that are accepted for use with the SI. Retrieved 2019-05-20.
  2. ^ a b "2018 CODATA Value: atomic mass constant". The NIST Reference on Constants, Units, and Uncertainty. NIST. 20 May 2019. Retrieved 2019-05-20.
  3. ^ The latest CODATA value has been substituted for the value listed in the 9th SI Brochure, since it supersedes that value.
  4. ^ This is a unit employed in geodesy and geophysics to express acceleration due to gravity.
  5. ^ As of 2019, the SI brochure no longer lists the unified atomic mass unit (symbol u) as being accepted for use with the SI units, though it notes its equivalence with the dalton in a footnote.