User:Atavoidirc/SI

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 Brochure^[1] because 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 they are otherwise commonly encountered worldwide.

Units officially accepted for use with the SI

Name	Symbol	Quantity	Value in SI units
minute	min	time	1 min = 60 s
hour	h	time	1 h = 60 min = 3 600 s
day	d	time	1 d = 24 h = 1440 min = 86 400 s
astronomical unit	au	length	1 au = 149 597 870 700 m
degree	°	plane angle	1° = ( $π$ /180) rad
minute	′	plane angle	1′ = (1/60)° = ( $π$ /10 800) rad
second	″	plane angle	1″ = (1/60)′ = (1/3 600)° = ( $π$ /648 000) rad
hectare	ha	area	1 ha = 1 hm² = 10 000 m²
litre	l, L	volume	1 l = 1 dm³ = 1 000 cm³ = 0.001 m³
tonne	t	mass	1 t = 1 Mg = 1 000 kg
dalton	Da	mass	1 Da = 1.66053906892(52)×10⁻²⁷ kg‍^[2] = 1.660 539 066 60(50) yg^{[note 1]}
electronvolt	eV	energy	1 eV = 1.602176634×10⁻¹⁹ J = 160.217 663 4 zJ
neper	Np	logarithmic ratio quantity	—
bel, decibel	B, dB	logarithmic ratio quantity	—

Changes to units mentioned in the SI

With the publication of the 9th SI brochure in 2019, the list of non-SI units listed in tables changed compared to the preceding SI brochures.^[3] The table below compares the status of each unit for which the status has changed between editions of the SI Brochure.

Name	Symbol	1st-3rd SI Brochures	4-6th SI Brochures	7th SI Brochure	8th SI Brochure	9th SI Brochure
astronomical unit	au^{[note 2]}	accepted	—	accepted	accepted	accepted
Parsec	pc	accepted	—	—	—	—
neper	Np	—	—	accepted	listed	accepted
bel	b	—	—	accepted	listed	accepted
decibel	db	—	—	—	listed	accepted
unified atomic mass unit	u	accepted	accepted	accepted	accepted	footnote only
dalton	Da	—	—	—	accepted	accepted
natural unit (n.u.) of speed	c₀	—	—	—	listed	—
n.u. of action	ħ	—	—	—	listed	—
n.u. of mass	m_e	—	—	—	listed	—
n.u. of time	ħ/(m_ec₀²)	—	—	—	listed	—
atomic unit (a.u.) of charge	e	—	—	—	listed	—
a.u. of mass	m_e	—	—	—	listed	—
a.u. of action	ħ	—	—	—	listed	—
a.u. of length	a₀	—	—	—	listed	—
a.u. of energy	E_h	—	—	—	listed	—
a.u. of time	ħ/E_h	—	—	—	listed	—
nautical mile	M	temporarily accepted	temporarily accepted	temporarily accepted	listed	—
knot	kn	temporarily accepted	temporarily accepted	temporarily accepted	listed	—
ångström	Å	temporarily accepted	temporarily accepted	temporarily accepted	listed	—
are	a	temporarily accepted	temporarily accepted	temporarily accepted	—	—
hectare	ha	temporarily accepted	temporarily accepted	temporarily accepted	accepted	accepted
barn	b	temporarily accepted	temporarily accepted	temporarily accepted	listed	—
bar	bar	temporarily accepted	temporarily accepted	temporarily accepted	listed	—
standard atmosphere	atm	temporarily accepted	listed	listed	—	—
gal	Gal	temporarily accepted	temporarily accepted	listed	listed	footnote only
curie	C	temporarily accepted	temporarily accepted	listed	—	—
roentgen	R	temporarily accepted	temporarily accepted	listed	—	—
rad	rad	temporarily accepted	temporarily accepted	listed	—	—
rem	rem	—	temporarily accepted	listed	—	—
erg	erg	listed	listed	listed	listed	—
dyne	dyn	listed	listed	listed	listed	—
poise	P	listed	listed	listed	listed	—
stokes	st	listed	listed	listed	listed	—
maxwell	Mx	listed	listed	listed	listed	—
gauss	G	listed	listed	listed	listed	—
ørsted	Oe	listed	listed	listed	listed	—
stilb	sb	listed	listed	listed	listed	—
phot	ph	listed	listed	listed	listed	—
fermi		listed	listed	listed	—	—
carat		listed	listed	listed	—	—
torr		listed	listed	listed	—	—
kilogram-force	kgf	listed	listed	—	—	—
calorie	cal	listed	listed	listed	—	—
micron	μ	listed	listed	listed	—	—
x-unit	xu	listed	listed	—	—	—
stilb	sb	listed	listed	—	—	—
gamma (Mass)	γ	listed	listed	listed	—	—
γ (magnetic flux density)	γ	listed	listed	—	—	—
lambda	λ	listed	listed	—	—	—
jansky	Jy	—	—	listed	—	—
millimetre of mercury	mmHg	—	—	—	listed	—

In this table, the status descriptions have the following meanings:

"accepted": The unit is accepted for use with the SI.
"temporarily accepted": The unit is accepted for use with the SI, but is planned to be phased out.
"listed": The unit is defined in a table of units in the brochure but not accepted for use with the SI.
"footnote only": The unit is defined in a footnote or side note, without any mention in the main text.
"—": There is no mention of the unit in the brochure, excluding historical appendices.

Other units defined but not officially sanctioned

The following table lists units that are effectively defined in side- and footnotes in the 9th SI brochure. Units that are mentioned without a definition or that occur in historical material recorded in the appendices are not included.

Name	Symbol	Quantity	Equivalent SI unit
gal^{[note 3]}	Gal	acceleration	1 Gal = 1 cm⋅s⁻² = 0.01 m⋅s⁻²
unified atomic mass unit^{[note 4]}	u	mass	1 u = 1 Da = 1.66053906892(52)×10⁻²⁷ kg‍^[2]
volt-ampere reactive	var	reactive power	1 var = 1 V⋅A

Notes and references

Notes

^ The latest CODATA value has been substituted for the value listed in the 9th SI Brochure, since it supersedes that value. An associated footnote gives an exact definition of the dalton.
^ The symbol given for the astronomical unit changed from ua in the 8th to au in the 9th SI Brochure.
^ This is a unit employed in geodesy and geophysics to express acceleration due to gravity.
^ 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.

References

^ Bureau international des poids et mesures, “Non-SI units that are accepted for use with the SI,” in: Le Système international d’unités (SI) / The International System of Units (SI), 9th ed. (Sèvres: 2019), ISBN 9789282222720, c. 4, pp. 145–146.
^ ^a ^b "2022 CODATA Value: atomic mass constant". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.
^ Bureau international des poids et mesures, Le Système international d’unités (SI) / The International System of Units (SI), 8th ed. (Sèvres: Organisation Intergouvernementale de la Convention du Mètre, 2006‑05), ISBN 9282222136.

[[Category:Non-SI metric units|*] [[Category:SI units|*]

[3] The latest CODATA value has been substituted for the value listed in the 9th SI Brochure, since it supersedes that value. An associated footnote gives an exact definition of the dalton.

[5] The symbol given for the astronomical unit changed from ua in the 8th to au in the 9th SI Brochure.

[6] This is a unit employed in geodesy and geophysics to express acceleration due to gravity.

[7] 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.

[bipm-1] Bureau international des poids et mesures, “Non-SI units that are accepted for use with the SI,” in: Le Système international d’unités (SI) / The International System of Units (SI), 9th ed. (Sèvres: 2019), ISBN 9789282222720, c. 4, pp. 145–146.

[physconst-mu-2] "2022 CODATA Value: atomic mass constant". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.

[4] Bureau international des poids et mesures, Le Système international d’unités (SI) / The International System of Units (SI), 8th ed. (Sèvres: Organisation Intergouvernementale de la Convention du Mètre, 2006‑05), ISBN 9282222136.

[1]

[2]

[note 1]

[3]

[note 2]

[note 3]

[note 4]

v t e SI units
Base units	ampere candela kelvin kilogram metre mole second
Derived units with special names	becquerel coulomb degree Celsius farad gray henry hertz joule katal lumen lux newton ohm pascal radian siemens sievert steradian tesla volt watt weber
See also	International System of Units Historical definitions of the SI base units 2019 revision of the SI Metric prefixes Conversion of units System of units of measurement
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