The International System of Units (SI)

en · official · sha256:cda56b70652b58497b97a21036988e3c2b7e92a80c82133dca270aa89a625b83

The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 × 10−7 newton per metre of length.

Referencing norms: AmpereByForceBetweenConductors

en · official · sha256:e0fb4dd0e599bac1b91546c9af5aa1a6650e0e66ac8a2c9d1a028b686f7c309c

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

Referencing norms: CandelaByLuminousEfficacy

en · official · sha256:e5eb5d219f4a2ccc5f2af5343fd9da756c5f197316eb25a3e71709b52673873d

The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.

Referencing norms: KelvinByTriplePointOfWater

en · official · sha256:fbe54492cb934a3683c27e50785952ae370f8ef1be02524b78c29aa84ddcbb93

The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram.

Referencing norms: KilogramByInternationalPrototype

en · official · sha256:aa913b40afb141ef278181a4252b925f790d5fd49e42b79b79c96a5945dd70fa

The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. The symbol, c0 (or

Referencing norms: MetreBySpeedOfLight

en · official · sha256:139b4e53cf1c1f254e9b624c1bb33033dfb95d81b98ad9c773fd42554fc05687

1. The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is “mol”.

Referencing norms: MoleByCarbonTwelve

en · official · sha256:29fd4f242ae205c2f4eff4c1829d0869885f4ceaad825d125a5010925fcc6edd

The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.

Referencing norms: SecondByCaesiumFrequency

en · official · sha256:6a98194b74b8b00e83c16010c51563c02e10c281acd51dde2e1bf1ce725026f7

Table 1. SI base units Base quantity SI base unit _________________________________ ___________________________ Name Symbol Name Symbol The symbols for quantities length l, x, r, etc. metre m are generally single letters mass m kilogram kg of the Latin or Greek time, duration t second s alphabets, printed in an electric current I, i ampere A italic font, and are thermodynamic temperature T kelvin K recommendations. amount of substance n mole mol The symbols for units are luminous intensity Iv candela cd mandatory, see chapter 5.

Referencing norms: base_unit, t2-a, t2-cd, t2-k, t2-kg, t2-m, t2-mol, t2-s

en · official · sha256:70c7c475f65a3e98d87c1ddf205e4d9809a2f2061473863c9e6f689fc1145e09

Table 3. Coherent derived units in the SI with special names and symbols SI coherent derived unit (a) —————————————————————————— Expressed Expressed in terms of in terms of Derived quantity Name Symbol other SI units SI base units plane angle radian (b) rad 1 (b) m/m solid angle steradian (b) sr (c) 1 (b) m2/m2 frequency hertz (d) Hz s−1 force newton N m kg s−2 pressure, stress pascal Pa N/m2 m−1 kg s−2 energy, work, joule J Nm m2 kg s−2 amount of heat power, radiant flux watt W J/s m2 kg s−3 electric charge, coulomb C sA amount of electricity electric potential difference, volt V W/A m2 kg s−3 A−1 electromotive force capacitance farad F C/V m−2 kg−1 s4 A2 electric resistance ohm Ω V/A m2 kg s−3 A−2 electric conductance siemens S A/V m−2 kg−1 s3 A2 magnetic flux weber Wb Vs m2 kg s−2 A−1 magnetic flux density tesla T Wb/m2 kg s−2 A−1 inductance henry H Wb/A m2 kg s−2 A−2 Celsius temperature degree Celsius (e) o C K luminous flux lumen lm cd sr (c) cd illuminance lux lx lm/m2 m−2 cd activity referred to becquerel (d) Bq s−1 a radionuclide (f) absorbed dose, gray Gy J/kg m2 s−2 specific energy (imparted), kerma dose equivalent, sievert (g) Sv J/kg m2 s−2 ambient dose equivalent, directional dose equivalent, personal dose equivalent catalytic activity katal kat s−1 mol

Referencing norms: base_exponent, special_unit, t4-bq, t4-c, t4-degc, t4-f, t4-gy, t4-h, t4-hz, t4-j, t4-kat, t4-lm, t4-lx, t4-n, t4-ohm, t4-pa, t4-rad, t4-s, t4-sr, t4-sv, t4-t, t4-v, t4-w, t4-wb, t4e-bq-a, t4e-bq-cd, t4e-bq-k, t4e-bq-kg, t4e-bq-m, t4e-bq-mol, t4e-bq-s, t4e-c-a, t4e-c-cd, t4e-c-k, t4e-c-kg, t4e-c-m, t4e-c-mol, t4e-c-s, t4e-degc-a, t4e-degc-cd, t4e-degc-k, t4e-degc-kg, t4e-degc-m, t4e-degc-mol, t4e-degc-s, t4e-f-a, t4e-f-cd, t4e-f-k, t4e-f-kg, t4e-f-m, t4e-f-mol, t4e-f-s, t4e-gy-a, t4e-gy-cd, t4e-gy-k, t4e-gy-kg, t4e-gy-m, t4e-gy-mol, t4e-gy-s, t4e-h-a, t4e-h-cd, t4e-h-k, t4e-h-kg, t4e-h-m, t4e-h-mol, t4e-h-s, t4e-hz-a, t4e-hz-cd, t4e-hz-k, t4e-hz-kg, t4e-hz-m, t4e-hz-mol, t4e-hz-s, t4e-j-a, t4e-j-cd, t4e-j-k, t4e-j-kg, t4e-j-m, t4e-j-mol, t4e-j-s, t4e-kat-a, t4e-kat-cd, t4e-kat-k, t4e-kat-kg, t4e-kat-m, t4e-kat-mol, t4e-kat-s, t4e-lm-a, t4e-lm-cd, t4e-lm-k, t4e-lm-kg, t4e-lm-m, t4e-lm-mol, t4e-lm-s, t4e-lx-a, t4e-lx-cd, t4e-lx-k, t4e-lx-kg, t4e-lx-m, t4e-lx-mol, t4e-lx-s, t4e-n-a, t4e-n-cd, t4e-n-k, t4e-n-kg, t4e-n-m, t4e-n-mol, t4e-n-s, t4e-ohm-a, t4e-ohm-cd, t4e-ohm-k, t4e-ohm-kg, t4e-ohm-m, t4e-ohm-mol, t4e-ohm-s, t4e-pa-a, t4e-pa-cd, t4e-pa-k, t4e-pa-kg, t4e-pa-m, t4e-pa-mol, t4e-pa-s, t4e-rad-a, t4e-rad-cd, t4e-rad-k, t4e-rad-kg, t4e-rad-m, t4e-rad-mol, t4e-rad-s, t4e-si-a, t4e-si-cd, t4e-si-k, t4e-si-kg, t4e-si-m, t4e-si-mol, t4e-si-s, t4e-sr-a, t4e-sr-cd, t4e-sr-k, t4e-sr-kg, t4e-sr-m, t4e-sr-mol, t4e-sr-s, t4e-sv-a, t4e-sv-cd, t4e-sv-k, t4e-sv-kg, t4e-sv-m, t4e-sv-mol, t4e-sv-s, t4e-t-a, t4e-t-cd, t4e-t-k, t4e-t-kg, t4e-t-m, t4e-t-mol, t4e-t-s, t4e-v-a, t4e-v-cd, t4e-v-k, t4e-v-kg, t4e-v-m, t4e-v-mol, t4e-v-s, t4e-w-a, t4e-w-cd, t4e-w-k, t4e-w-kg, t4e-w-m, t4e-w-mol, t4e-w-s, t4e-wb-a, t4e-wb-cd, t4e-wb-k, t4e-wb-kg, t4e-wb-m, t4e-wb-mol, t4e-wb-s

en · official · sha256:033ee040cd3b4a114dbe4e5fa1373cbbe6336dfe99324ee9ae51b65f9c7c871e

Table 5. SI prefixes Telecommunications and electronics. The names and symbols for the prefixes Factor Name Symbol Factor Name Symbol corresponding to 210, 220, 230, 240, 250, and 260 are, 101 deca da 10−1 deci d respectively: kibi, Ki; mebi, 102 hecto h 10−2 centi c Mi; gibi, Gi; tebi, Ti; pebi, 103 kilo k 10−3 milli m Pi; and exbi, Ei. Thus, for 106 mega M 10−6 micro µ example, one kibibyte would be written: 109 giga G 10−9 nano n 1 KiB = 210 B = 1024 B, 1012 tera T 10−12 pico p where B denotes a byte. 1015 peta P 10−15 femto f Although these prefixes are 1018 exa E 10−18 atto a not part of the SI, they 1021 zetta Z 10−21 zepto z should be used in the field 1024 yotta Y 10−24 yocto y of information technology

Referencing norms: LongStandingPrefix, prefix_factor, prefix_in_8th_edition, t5-E, t5-G, t5-M, t5-P, t5-T, t5-Y, t5-Z, t5-a, t5-c, t5-d, t5-da, t5-f, t5-h, t5-k, t5-m, t5-n, t5-p, t5-u, t5-y, t5-z, t7-E, t7-G, t7-M, t7-P, t7-Q, t7-R, t7-T, t7-Y, t7-Z, t7-a, t7-c, t7-d, t7-da, t7-f, t7-h, t7-k, t7-m, t7-n, t7-p, t7-q, t7-r, t7-u, t7-y, t7-z

en · official · sha256:50ec898ce13fb38212455e5847b2ff223fbacb138b28b57319764cd4ef10f256

Table 6. Non-SI units accepted for use with the International System of Units Quantity Name of unit Symbol for unit Value in SI units time minute min 1 min = 60 s hour (a) h 1 h = 60 min = 3600 s day d 1 d = 24 h = 86 400 s plane angle degree (b, c) o 1o = (π/180) rad minute ′ 1′ = (1/60)o = (π/ 10 800) rad second (d) ″ 1″ = (1/60)′ = (π/ 648 000) rad area hectare (e) ha 1 ha = 1 hm2 = 104 m2 volume litre (f) L, l 1 L = 1 l = 1 dm3 = 103 cm3 = 10−3 m3 mass tonne (g) t 1 t = 103 kg

en · official · sha256:db245688b99edbdfcbd6564bfe291cefaa4af217ce12e0885bce05255ce5af8b

26th CGPM, 2018: revision of the International System of Units, the SI 194 (to enter into force on 20 May 2019)

Referencing norms: AmpereByElementaryCharge, KelvinByBoltzmannConstant, KilogramByPlanckConstant, MoleByAvogadroConstant, SIDefinedByConstants

en · official · sha256:c9c4db4b2e2e564c569165ac05736da2065ab50827c2613fe78a88fbdb6a19da

27th CGPM, 2022: decides to add ronna, ronto, quetta, and quecto to the 196

Referencing norms: prefix_added_2022

en · official · sha256:da9a754f29e9b1412a8e324261700aa844550bca5e2efbe04d4362790bc2c8b3

 On the extension of the range of SI prefixes (CR, 397 and Metrologia, 2023, 60, 013001) Resolution 3 The General Conference on Weights and Measures (CGPM), at its 27th meeting, recalling that decisions were made at previous meetings when it was considered timely to extend the range of SI prefixes including Resolution 12 (paragraph 3) adopted by the CGPM at its 11th meeting (1960), Resolution 8 adopted by the CGPM at its 12th meeting (1964), Resolution 10 adopted by the CGPM at its 15th meeting (1975), and Resolution 4 adopted by the CGPM at its 19th meeting (1991), considering − the essential role of the International System of Units (SI) in providing confidence in the accuracy and global comparability of measurements needed for international trade, manufacturing, human health and safety, protection of the environment, global climate studies and scientific research, − the benefits of encouraging the use of SI units by providing new SI prefixes for scientific communities that depend on measurements that are not covered by the current range, Appendix 1 • 197 − the needs of data science in the near future to express quantities of digital information using orders of magnitude in excess of 1024, − the importance of timely action to prevent unofficial prefix names being de facto adopted in other communities, decides to add to the list of SI prefixes to be used for multiples and submultiples of units the following prefixes: Multiplying factor Name Symbol 1027 ronna R 10−27 ronto r 1030 quetta Q 10−30 quecto q

Referencing norms: PrefixAdded2022, prefix_added_2022, r3-Q, r3-R, r3-q, r3-r

en · official · sha256:ee5d176bd7c10a5fd04b88fca6c4230500668da6aac99d1d3c36a4cefebe9e2e

The ampere, symbol A, is the SI unit of electric current. It is defined by taking the fixed numerical value of the elementary charge, e, to be 1.602 176 634 × 10−19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of ∆νCs.

Referencing norms: AmpereByElementaryCharge, ElementaryChargeUnitVerified

en · official · sha256:e0ef37a23e1dd6bb5def7debca8079b9612fe024405e5bef9b40d84e7ecb37ec

The candela, symbol cd, is the SI unit of luminous intensity in a given direction. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 1012 Hz, Kcd, to be 683 when expressed in the unit lm W−1, which is equal to cd sr W−1, or cd sr kg−1 m−2 s3, where the kilogram, metre and second are defined in terms of h, c and ∆νCs.

Referencing norms: CandelaByLuminousEfficacy, LuminousEfficacyUnitVerified

en · official · sha256:e7d9ee6b2f490124223d1accc13282a3b5738bb04df8ca36916189010fd2388d

The kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by taking the fixed numerical value of the Boltzmann constant, k, to be 1.380 649 × 10−23 when expressed in the unit J K−1, which is equal to kg m2 s−2 K−1, where the kilogram, metre and second are defined in terms of h, c and ∆νCs.

Referencing norms: BoltzmannUnitVerified, KelvinByBoltzmannConstant

en · official · sha256:96dae548d302b9211c1c70f6e206bf377de3b0c9fbb7327d36e875da4063d572

The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant, h, to be 6.626 070 15 × 10−34 when expressed in the unit J s, which is equal to kg m2 s−1, where the metre and the second are defined in terms of c and ∆νCs.

Referencing norms: KilogramByPlanckConstant, PlanckUnitVerified

en · official · sha256:9776d44ec57958c405378e1585c171bf44eebe01426be027f959a77064d4c8e0

The metre, symbol m, is the SI unit of length. It is defined by taking the fixed numerical value of the speed of light in vacuum, c, to be 299 792 458 when expressed in the unit m s−1, where the second is defined in terms of the caesium frequency ∆νCs.

Referencing norms: MetreBySpeedOfLight

en · official · sha256:a11e8e01b96d54037f81044afa61838d441ef84f48bcdf4855c3a7ebf94bac16

The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.022 140 76 × 1023 elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol−1 and is called the Avogadro number.

Referencing norms: MoleByAvogadroConstant

en · official · sha256:a2b330de77b8fb6a298ffbbc5e22952db51f936a67c6a911f6df4afc0a5df01b

The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency, ∆νCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s−1.

Referencing norms: SecondByCaesiumFrequency

en · official · sha256:186bea9a7e8e45241bf08305fc7f7d05fee96c1d1df4b8b841043bb2a9deeb52

The International System of Units, the SI, is the system of units in which • the unperturbed ground state hyperfine transition frequency of the caesium 133 atom, ∆νCs, is 9 192 631 770 Hz, • the speed of light in vacuum, c, is 299 792 458 m/s, • the Planck constant, h, is 6.626 070 15 × 10−34 J s, • the elementary charge, e, is 1.602 176 634 × 10−19 C, • the Boltzmann constant, k, is 1.380 649 × 10−23 J/K, • the Avogadro constant, NA, is 6.022 140 76 × 1023 mol−1, • the luminous efficacy of monochromatic radiation of frequency 540 × 1012 Hz, Kcd, is 683 lm/W,

Referencing norms: SIDefinedByConstants, defining_constant, defining_constant_quantity

en · official · sha256:a2129c13bcd907dfdd657785e5d386188697524d86979439e0d86f0898e496a4

where the hertz, joule, coulomb, lumen, and watt, with unit symbols Hz, J, C, lm, and W, respectively, are related to the units second, metre, kilogram, ampere, kelvin, mole, and candela, with unit symbols s, m, kg, A, K, mol, and cd, respectively, according to Hz = s–1, J = kg m2 s– 2, C = A s, lm = cd sr, and W = kg m2 s–3. The numerical values of the seven defining constants have no uncertainty.

Referencing norms: ExactConstantHasCoincidingBounds

en · official · sha256:81773254636a642ed6da3aec77e32cafb409eae407b17017686a27135b328f9a

The unit of Celsius temperature is the degree Celsius, symbol °C, which is by definition equal in magnitude to the unit kelvin. A difference or interval of temperature may be expressed in kelvins or in degrees Celsius, the numerical value of the temperature difference being the same in either case. However, the numerical value of a Celsius temperature expressed in degrees Celsius is related to the numerical value of the thermodynamic temperature expressed in kelvins by the relation t/°C = T/K − 273.15

Referencing norms: CelsiusFromKelvin, DegreeCelsiusIntervalVerified, thermodynamic_temperature

en · official · sha256:b9e6a117312c189b30c283ce54aee8fdfdea00c8fe550f1c0236e766dc9186cb

Derived units are defined as products of powers of the base units. When the numerical factor of this product is one, the derived units are called coherent derived units. The base and coherent derived units of the SI form a coherent set, designated the set of coherent SI units. The word “coherent” here means that equations between the numerical values of quantities take exactly the same form as the equations between the quantities themselves.

Referencing norms: BaseUnitIsCoherent

en · official · sha256:ba07f1b3c6f8c3772a950b6e0b74315712b3c468206b9b83cc70ec6b0ee93720

The seven base units and 22 units with special names and symbols may be used in combination to express the units of other derived quantities. Since the number of quantities is without limit, it is not possible to provide a complete list of derived quantities and derived units. Table 5 lists some examples of derived quantities and the corresponding coherent derived units expressed in terms of base units. In addition, Table 6 lists examples of coherent derived units whose names and symbols also include derived units. The complete set of SI units includes both the coherent set and the multiples and sub-multiples formed by using the SI prefixes.

Referencing norms: CoherentUnitIsSiUnit, PrefixAttachesToUnit

en · official · sha256:c093af4db37dce32abaf0950fef702d7f2a024f35700fa39bfc5a3875e4db083

The CGPM has adopted a series of prefixes for use in forming the decimal multiples and sub- multiples of the coherent SI units (see chapter 3). They are convenient for expressing the values of quantities that are much larger than or much smaller than the coherent unit. However, when prefixes are used with SI units, the resulting units are no longer coherent, because the prefix introduces a numerical factor other than one. Prefixes may be used with any of the 29 SI units with special names with the exception of the base unit kilogram, which is further explained in chapter 3.

Referencing norms: pa-a, pa-bq, pa-c, pa-cd, pa-degc, pa-f, pa-g, pa-gy, pa-h, pa-hz, pa-j, pa-k, pa-kat, pa-lm, pa-lx, pa-m, pa-mol, pa-n, pa-ohm, pa-pa, pa-rad, pa-s, pa-si, pa-sr, pa-sv, pa-t, pa-v, pa-w, pa-wb, prefix_attaches_to

en · official · sha256:515a61fe3b5e76008a87be79f0c0d988a935aee92c2d22abefed37564313eba0

Some of the coherent derived units in the SI are given special names. Table 4 lists 22 SI units with special names. Together with the seven base units (Table 2) they form the core of the set of SI units. All other SI units are combinations of some of these 29 units.

Referencing norms: SpecialNamedUnitIsCoherent

en · official · sha256:7271a37ae1b8b3f1bdc28994ba3fc71acb0ddbeb089df35c4c5052706b44e846

Compound prefix symbols, i.e. prefix symbols formed by the juxtaposition of two or more prefix symbols, are not permitted. This rule also applies to two or more compound prefix names.

Referencing norms: NoCompoundPrefix

en · official · sha256:f100b1f76283e004d1b8c8b32f818afc84c62ffb98e7a0416a2057b8fbaec48b

The grouping formed by a prefix symbol attached to a unit symbol constitutes a new inseparable unit symbol (forming a multiple or sub-multiple of the unit concerned) that can be raised to a positive or negative power and that can be combined with other unit symbols to form compound unit symbols.

Referencing norms: PrefixAttachesToUnit

en · official · sha256:287904741f4b52ca7afad9cf582c6821a418beb6ad4c42871ec10793d20aecd9

Decimal multiples and submultiples ranging from 1030 to 10−30 are provided for use with the SI units. The names and symbols of these multiple and sub-multiple prefixes are presented in Table 7.

en · official · sha256:c745c0e5afd6eb4cc7d18f307b66172592a9256bc528d5e54d8997168a615dca

For historical reasons, the kilogram is the only coherent SI unit that includes a prefix in its name and symbol. Names and symbols for decimal multiples and sub-multiples of the unit of mass are formed by attaching prefix names and symbols to the unit name “gram” and the unit symbol “g” respectively. For example, 10−6 kg is written as milligram, mg, not as microkilogram, µkg.

Referencing norms: MilligramScaleVerified, NoPrefixOnKilogram, pa-a, pa-bq, pa-c, pa-cd, pa-degc, pa-f, pa-g, pa-gy, pa-h, pa-hz, pa-j, pa-k, pa-kat, pa-lm, pa-lx, pa-m, pa-mol, pa-n, pa-ohm, pa-pa, pa-rad, pa-s, pa-si, pa-sr, pa-sv, pa-t, pa-v, pa-w, pa-wb, prefix_attaches_to

en · official · sha256:29b0a429548094c549dbe93554a0d57bb24f970ccc798244745252608e18d734

It is recognized that some non-SI units are widely used and that this is expected to continue for many years. It is therefore important to recall the values of these non-SI units in terms of SI units, because the SI is the internationally agreed reference with respect to which all other units are defined. A non-exhaustive list of non-SI units is given in Table 8, grouped into indicative unit categories to aid explanation.

Referencing norms: NonSiUnitAccepted

en · official · sha256:7af45fae4cb7a313e6c6425db7389d026287af5edadb25837e7fd871ec1e9fbb

Table 1. The seven defining constants of the SI and the seven corresponding units they define ___________________________________________________________________________ Defining constant Symbol Numerical value Unit ___________________________________________________________________________ hyperfine transition frequency of Cs ∆νCs 9 192 631 770 Hz speed of light in vacuum c 299 792 458 m s−1 Planck constant h 6.626 070 15 × 10−34 Js elementary charge e 1.602 176 634 × 10−19 C Boltzmann constant k 1.380 649 × 10 −23 J K−1 Avogadro constant NA 6.022 140 76 × 1023 mol−1 luminous efficacy Kcd 683 lm W−1

Referencing norms: defining_constant, defining_constant_quantity, t1-c, t1-dnu-cs, t1-e, t1-h, t1-k, t1-kcd, t1-na, t1q-c, t1q-dnu-cs, t1q-e, t1q-h, t1q-k, t1q-kcd, t1q-na, ExactConstantHasCoincidingBounds

en · official · sha256:bdd9a6b3aadcc3e36539d3972cbe501a92940a3328bf1920d89660a3acc9e77b

Table 2. SI base units _____________________________________________________________________________ Base quantity Base unit _____________________________________________________________________________ Name Typical symbol Name Symbol _____________________________________________________________________________ time t second s length l, x, r, etc. metre m mass m kilogram kg electric current I, i ampere A thermodynamic temperature T kelvin K amount of substance n mole mol luminous intensity Iv candela cd

Referencing norms: BaseUnitIsCoherent, TableRowVerifiedByRegistry, base_unit, registry_name, rn-a, rn-bq, rn-c, rn-cd, rn-f, rn-gy, rn-h, rn-hz, rn-j, rn-k, rn-kat, rn-kg, rn-lm, rn-lx, rn-m, rn-mol, rn-n, rn-ohm, rn-pa, rn-s, rn-si, rn-sv, rn-t, rn-v, rn-w, rn-wb, t2-a, t2-cd, t2-k, t2-kg, t2-m, t2-mol, t2-s

en · official · sha256:fd0d2e3ba1b4f130bcf6fbeb2bc54f86b671e4e4cab5a195f3a165f8c72d8070

Table 4. The 22 SI units with special names and symbols _____________________________________________________________________________________________ Special name Unit expressed in Unit expressed in Derived quantity of unit Symbol terms of base units (a) terms of other SI units ______________________________________________________________________________________________ plane angle radian (b) rad (b) 1 solid angle steradian (c) sr (c) 1 frequency hertz (d) Hz s−1 force newton N kg m s−2 pressure, stress pascal Pa kg m−1 s−2 N/m2 energy, work, joule J kg m2 s−2 Nm amount of heat power, radiant flux watt W kg m2 s−3 J/s electric charge coulomb C As electric potential difference (e) volt V kg m2 s−3 A−1 W/A capacitance farad F kg−1 m−2 s4 A2 C/V electric resistance ohm Ω kg m2 s−3 A−2 V/A electric conductance siemens S kg −1 m−2 s3 A2 A/V magnetic flux weber Wb kg m2 s−2 A−1 Vs magnetic flux density tesla T kg s−2 A−1 Wb/m2 inductance henry H kg m 2 s−2 A−2 Wb/A 134 • The International System of Units Celsius temperature degree Celsius (f) °C K luminous flux lumen lm cd sr (g) cd sr illuminance lux lx cd sr m−2 lm/m2 activity referred to becquerel Bq s−1 a radionuclide (d, h) absorbed dose, kerma gray Gy m2 s−2 J/kg dose equivalent sievert (i) Sv m2 s−2 J/kg catalytic activity katal kat mol s −1

Referencing norms: DegreeCelsiusIntervalVerified, FaradViaOtherUnitsVerified, GrayViaOtherUnitsVerified, HenryViaOtherUnitsVerified, JouleViaOtherUnitsVerified, LuxViaOtherUnitsVerified, OhmViaOtherUnitsVerified, PascalViaOtherUnitsVerified, SiemensViaOtherUnitsVerified, SievertViaOtherUnitsVerified, SpecialNamedUnitIsCoherent, TableRowVerifiedByRegistry, TeslaViaOtherUnitsVerified, VoltViaOtherUnitsVerified, WattViaOtherUnitsVerified, WeberViaOtherUnitsVerified, base_exponent, registry_name, rn-a, rn-bq, rn-c, rn-cd, rn-f, rn-gy, rn-h, rn-hz, rn-j, rn-k, rn-kat, rn-kg, rn-lm, rn-lx, rn-m, rn-mol, rn-n, rn-ohm, rn-pa, rn-s, rn-si, rn-sv, rn-t, rn-v, rn-w, rn-wb, special_unit, t4-bq, t4-c, t4-degc, t4-f, t4-gy, t4-h, t4-hz, t4-j, t4-kat, t4-lm, t4-lx, t4-n, t4-ohm, t4-pa, t4-rad, t4-s, t4-sr, t4-sv, t4-t, t4-v, t4-w, t4-wb, t4e-bq-a, t4e-bq-cd, t4e-bq-k, t4e-bq-kg, t4e-bq-m, t4e-bq-mol, t4e-bq-s, t4e-c-a, t4e-c-cd, t4e-c-k, t4e-c-kg, t4e-c-m, t4e-c-mol, t4e-c-s, t4e-degc-a, t4e-degc-cd, t4e-degc-k, t4e-degc-kg, t4e-degc-m, t4e-degc-mol, t4e-degc-s, t4e-f-a, t4e-f-cd, t4e-f-k, t4e-f-kg, t4e-f-m, t4e-f-mol, t4e-f-s, t4e-gy-a, t4e-gy-cd, t4e-gy-k, t4e-gy-kg, t4e-gy-m, t4e-gy-mol, t4e-gy-s, t4e-h-a, t4e-h-cd, t4e-h-k, t4e-h-kg, t4e-h-m, t4e-h-mol, t4e-h-s, t4e-hz-a, t4e-hz-cd, t4e-hz-k, t4e-hz-kg, t4e-hz-m, t4e-hz-mol, t4e-hz-s, t4e-j-a, t4e-j-cd, t4e-j-k, t4e-j-kg, t4e-j-m, t4e-j-mol, t4e-j-s, t4e-kat-a, t4e-kat-cd, t4e-kat-k, t4e-kat-kg, t4e-kat-m, t4e-kat-mol, t4e-kat-s, t4e-lm-a, t4e-lm-cd, t4e-lm-k, t4e-lm-kg, t4e-lm-m, t4e-lm-mol, t4e-lm-s, t4e-lx-a, t4e-lx-cd, t4e-lx-k, t4e-lx-kg, t4e-lx-m, t4e-lx-mol, t4e-lx-s, t4e-n-a, t4e-n-cd, t4e-n-k, t4e-n-kg, t4e-n-m, t4e-n-mol, t4e-n-s, t4e-ohm-a, t4e-ohm-cd, t4e-ohm-k, t4e-ohm-kg, t4e-ohm-m, t4e-ohm-mol, t4e-ohm-s, t4e-pa-a, t4e-pa-cd, t4e-pa-k, t4e-pa-kg, t4e-pa-m, t4e-pa-mol, t4e-pa-s, t4e-rad-a, t4e-rad-cd, t4e-rad-k, t4e-rad-kg, t4e-rad-m, t4e-rad-mol, t4e-rad-s, t4e-si-a, t4e-si-cd, t4e-si-k, t4e-si-kg, t4e-si-m, t4e-si-mol, t4e-si-s, t4e-sr-a, t4e-sr-cd, t4e-sr-k, t4e-sr-kg, t4e-sr-m, t4e-sr-mol, t4e-sr-s, t4e-sv-a, t4e-sv-cd, t4e-sv-k, t4e-sv-kg, t4e-sv-m, t4e-sv-mol, t4e-sv-s, t4e-t-a, t4e-t-cd, t4e-t-k, t4e-t-kg, t4e-t-m, t4e-t-mol, t4e-t-s, t4e-v-a, t4e-v-cd, t4e-v-k, t4e-v-kg, t4e-v-m, t4e-v-mol, t4e-v-s, t4e-w-a, t4e-w-cd, t4e-w-k, t4e-w-kg, t4e-w-m, t4e-w-mol, t4e-w-s, t4e-wb-a, t4e-wb-cd, t4e-wb-k, t4e-wb-kg, t4e-wb-m, t4e-wb-mol, t4e-wb-s

en · official · sha256:12e43dffddcc8f179c629bcd2a1de930f970f632899c8a4da3f5ff3643c05559

Table 7. SI prefixes _____________________________________________________________________________ Factor Name Symbol Factor Name Symbol 101 deca da 10−1 deci d 10 2 hecto h 10−2 centi c 10 3 kilo k 10 −3 milli m 106 mega M 10−6 micro µ 109 giga G 10−9 nano n 10 12 tera T 10 −12 pico p 1015 peta P 10−15 femto f 1018 exa E 10−18 atto a 1021 zetta Z 10−21 zepto z 10 24 yotta Y 10 −24 yocto y 10 27 ronna R 10 −27 ronto r 1030 quetta Q 10−30 quecto q

Referencing norms: CentimetreScaleVerified, DecimetreScaleVerified, KilometreScaleVerified, LongStandingPrefix, MilligramScaleVerified, MillimetreScaleVerified, MillimoleScaleVerified, PrefixAdded2022, prefix_factor, prefix_in_8th_edition, t5-E, t5-G, t5-M, t5-P, t5-T, t5-Y, t5-Z, t5-a, t5-c, t5-d, t5-da, t5-f, t5-h, t5-k, t5-m, t5-n, t5-p, t5-u, t5-y, t5-z, t7-E, t7-G, t7-M, t7-P, t7-Q, t7-R, t7-T, t7-Y, t7-Z, t7-a, t7-c, t7-d, t7-da, t7-f, t7-h, t7-k, t7-m, t7-n, t7-p, t7-q, t7-r, t7-u, t7-y, t7-z

en · official · sha256:57b8a23b0a6cc65a2174b77ede19272cc5689173c83bf8a600ed04f5a8699743

Table 8. Non-SI units Symbol Unit category Quantity Name of unit Value in SI units for unit Long-standing time minute min 1 min = 60 s units of time and hour h 1 h = 60 min = 3600 s angle day d 1 d = 24 h = 86 400 s plane and degree ° 1° = (π/180) rad phase angle minute ′ 1′ = (1/60)° = (π/10 800) rad second (a) ″ 1″ = (1/60)′ = (π/648 000) rad Historical names area are (b) a 1 a = 1 dam2 = 102 m2 for decimal hectare (b) ha 1 ha = 1 hm2 = 104 m2 multiples and barn (c) b 1 b = 100 fm2 = 10−28 m2 submultiples of SI units volume litre (d) l, L 1 l = 1 L = 1 dm3 = 10−3 m3 mass tonne (e) t 1 t = 1 Mg = 103 kg length angstrom (f) Å 1 Å = 0.1 nm = 10−10 m acceleration gal (g) Gal 1 Gal = 1 cm/s2 = 10−2 m/s2 pressure bar (h) bar 1 bar = 0.1 MPa = 105 Pa Internationally mass dalton (i) Da 1 Da = recognised units 1.660 539 068 92(52) × 10−27 kg that are not decimal multiples length astronomical unit (j) au 1 au = 149 597 870 700 m or submultiples nautical mile (k) 1 nautical mile = 1852 m of SI units speed knot (k) 1 nautical mile per hour = (1852/3600) m/s energy electronvolt (l) eV 1 eV = 1.602 176 634 × 10−19 J Units used in logarithmic neper (m) Np (m) specialized ratio quantities bel (m) B (m) technical decibel (m) dB (m) disciplines reactive power var (n) var 1 var = 1 V A = 1 W

Referencing norms: AstronomicalUnitValueVerified, DayValueVerified, HectareValueVerified, HourValueVerified, LitreValueVerified, MinuteValueVerified, NonSiUnitAccepted, TonneValueVerified, non_si_unit, t8-a, t8-ang, t8-arcmin, t8-arcsec, t8-au, t8-b, t8-bar, t8-bel, t8-d, t8-da, t8-db, t8-deg, t8-ev, t8-gal, t8-h, t8-ha, t8-kn, t8-l, t8-min, t8-nm, t8-np, t8-t, t8-var