Non-SI units mentioned in the SI

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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][2] 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 SI[edit]

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[1][3] length (SI unit multiple) 1 au = 149597870700 m (decimal unit multiple)
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 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
unified atomic mass unit
Da
u
mass 1 Da = 1 u = 1.660539040(20)×10−27 kg
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 sanctioned[edit]

Name Symbol Quantity Equivalent SI unit
gal Gal acceleration 1 Gal = 1 cm/s2 = 0.01 m/s2 (employed in geodesy and geophysics to express acceleration due to gravity)
standard atmosphere atm pressure 1 atm = 101325 Pa exactly (commonly used in atmospheric meteorology, in oceanography and for pressures within liquids, or in industry for pressures within containers of liquefied gas)
dyne per square centimetre (barye) Ba pressure 1 Ba = 0.1 Pa = 0.1 N/m2 = 100 g·cm−1·s−2

See also[edit]

References[edit]

  1. ^ a b "§4 Non-SI units that are accepted for use with the SI". SI brochure (9th edition). BIPM. 2019 [2019]. Retrieved 2019-05-20.
  2. ^ Taylor, Barry N. (ed.) (2001). "The International System of Units (SI)" (PDF). Special Publication 330. Gaithersburg, Maryland: National Institute of Standards and Technology (NIST).CS1 maint: Extra text: authors list (link)
  3. ^ "Manuscript Preparation: AJ & ApJ Author Instructions". American Astronomical Society. Retrieved 2015-06-15.