Units dictionary: si units dictionary

namespace: http://www.xml-cml.org/units/siUnits

idtitlesymbolunitTypemultSISI.iddescriptionunitType description
a.m-1ampere per metreA.m-1magnetic_field_strength1.0a.m-1 not yet added Magnetic field strength
a.m-2ampere per square metreA.m-2electric_current_density1.0a.m-2 not yet added electric current density
ampereampereAcurrent1.0ampere This is equivalent to setting the permeability of vacuum to pi*4E-7 Hm^-1. Prior to 1948, the International Ampere (equal to 0.99985 A) was used; it was defined in terms of the electrolytic deposition rate of silver. Electrical current
becquerelBecquerelBqradioactivity1.0becquerel This, therefore, has the same dimensionality as the hertz (s^-1, reciprocal time) - a frequency, in other words. The reason for having a specific unit for radioactivity is slightly unusual; it was specifically introduced because of the dangers to human health which might arise from mistakes involving the units reciprocal second. Using the becquerel unit, a more active (and so, all the other things fixed, more dangerous) source has a higher number. Using 1/s or s as a second instead may lead to confusion. Radioactivity
c.kg-1coulomb per kilogramC.kg-1exposure1.0c.kg-1 not yet added exposure (X and gamma rays)
c.m-3coulomb per cubic metreC.m-3electric_charge_density1.0c.m-3 not yet added electric charge density
candelacandelacdluminous_intensity1.0candela This is based on an older unit, the candlepower, which was referenced to the luminous intensity of a "standard candle" of known composition. The frequency chosen is in the visible spectrum near green, which is within the range where the human eye is most sensitive. Luminous intensity
cd.m-2candela per square metrecd.m-2luminance1.0cd.m-2 not yet added Luminance
coulombCoulombCelectric_charge1.0coulomb Also the unit of electric flux. The Coulomb could, in principle, be defined in terms of the elementary charge of the electron and the Josephson and von Klitzing constants; in this case, the kilogram would become a derived rather than fundamental unit. Electric charge
f.m-1farad per metreF.m-1permittivity1.0f.m-1 not yet added Permittivity
faradFaradFelectric_capacitance1.0farad Capacitance is a measure of the total amount of electric charge stored for a given electric potential. The farad is a very large unit; typical capacitors are in the microfarad to picofarad range. Although the farad is named after Michael Faraday, it should not be confused with the Faraday - an older unit of capacitance. Electric capacitance
grayGrayGyradioactive_absorbed_dose1.0gray Note that these are the same units as the sievert. To avoid any risk of confusion between the absorbed dose and the equivalent dose, one must use the corresponding special units, namely the gray instead of the joule per kilogram for absorbed dose and the sievert instead of the joule per kilogram for the dose equivalent. absorbed dose (of ionising radiation)
gy.s-1gray per secondGy.s-1absorbed_dose_rate1.0gy.s-1 not yet added absorbed dose rate
h.m-1henry per metreH.m-1permeability1.0h.m-1 not yet added Permeability (electromagnetism)
henryHenryHmagnetic_inductance1.0henry Inductance is a measure of how much magnetic flux is produced for a given circuit. Inductance
hertzHertzHzfrequency1.0hertz Periodically varying angles are typically not expressed in Hz, but instead in an appropriate angular unit (such as radians per second). Frequency
j.k-1joule per kelvinJ.K-1heat_capacity1.0j.k-1 not yet added Entropy, Heat Capacity
j.k-1.kg-1joule per kilogram kelvinJ.K-1.kg-1specific_heat_capacity1.0j.k-1.kg-1 not yet added Specific heat capacity
j.k-1.mol-1joule per kelvin moleJ.K-1.mol-1molar_heat_capacity1.0j.k-1.mol-1 not yet added molar heat capacity
j.kg-1joule per kilogramJ.kg-1specific_energy1.0j.kg-1 not yet added specific energy
j.m-1joule per metreJ.m-1energy_length_gradient1.0j.m-1 Although formally identical to force, many authors report energy gradients as energy per unit length and this unitType preserves the dimensional representation. energy_length_gradient
j.m-3joule per cubic metreJ.m-3energy_density1.0j.m-3 not yet added energy density
j.mol-1joule per moleJ.mol-1molar_energy1.0j.mol-1 not yet added molar energy
jouleJouleJenergy1.0joule This is dimensionally, but not semantically, equivalent to the newton metre, which is typically used as a unit of torque. It is also, significantly, the work required to move an electric charge of one coulomb through an electric potential difference of one volt. energy
kkelvinKtemperature1.0k A temperature in Kelvin is measured with respect to absolute zero - where, except for zero-point motion, molecular motion stops. The unit is named after William Thomson, first Baron Kelvin, a Scottish physicist and engineer. Temperature
katalKatalkatcatalytic_activity1.0katal The katal is not used to express the rate of a reaction; that is expressed in moles per second. Rather, it is used to express catalytic activity which is a property of the catalyst. The katal is invariant of the measurement procedure, but the numerical quantity value is not and depends on the experimental conditions. Therefore, in order to define the quantity of a catalyst, the rate of conversion of a defined chemical reaction has to be specified, preferably of the first order, under strictly controlled conditions. Catalytic activity
kgkilogramkgmass1.0kg It is the only SI base unit that employs a prefix, and the only SI unit that is still defined in relation to an artifact (a platinum-iridium mass) rather than to a fundamental physical property. Mass
kg-1.m3cubic metre per kilogramkg-1.m3specific_volume1.0kg-1.m3 not yet added specific volume
kg.m-3Kilogram per cubic metrekg.m-3mass_density1.0kg.m-3 not yet added Density
mmetremlength1.0m The modern metre dates from 1791, when it was defined one ten-millionth of the length of the earth's meridian along a quadrant; it became France's official unit of length in 1793. Until 1960, the metre (like the kilogram) was defined by a prototype - in this case, a platinum-iridium bar; in 1960, the SI defined the metre as 1650763.73 wavelengths of the orange-red emission line (the 2p10 - 5d5 transition) in the EM spectrum of Krypton-86 in vacuum. Since 1983, the present definition has been used. Length
m-1reciprocal metrem-1wavenumber1.0m-1 not yet added Wavenumber
m-3.molmole per cubic metrem-3.molamount_concentration1.0m-3.mol not yet added amount (-of-substance) concentration
m.s-1Metre per secondm.s-1velocity1.0m.s-1 not yet added Velocity
m.s-2Metre per second squaredm.s-2acceleration1.0m.s-2 not yet added Acceleration
m2Square metrem2area1.0m2 not yet added Area
m2.s-1square metre per secondm2.s-1kinematic_viscosity1.0m2.s-1 not yet added Diffusion coefficient, kinematic viscosity
m3Cubic metrem3volume1.0m3 not yet added Volume
m3.mol-1cubic metre per molem3.mol-1molar_volume1.0m3.mol-1 not yet added molar volume
molmolemolamount1.0mol The number of atoms in 12 grams of carbon 12 is commonly known as Avogadro's number; it is approximately 6.0221415E23. Prior to 1959, IUPAP and IUPAC defined the mole in terms of oxygen (though the definitions were slightly different from each other); in 1959/1960, the two organizations unified on the present definition. Amount of substance
molalityMolality_i_m__i_molality1.0molality not yet added Concentration (moles of substance per mass of solution)
molarityMolarity_i_M__i_molarity1.0molarity not yet added Concentration (moles of substance per volume of solution)
n.mnewton metreN.mtorque1.0n.m not yet added Torque, moment of force
n.m-1newton per metreN.m-1 = J.m-2surface_tension1.0n.m-1 not yet added Surface tension
n.m.snewton metre secondN.m.sangular_momentum1.0n.m.s not yet added Angular momentum
n.snewton secondN.smomentum1.0n.s not yet added Momentum
newtonNewtonNforce1.0newton Named after Sir Isaac Newton, the Newton was adopted as the name for the MKS (direct predecessor of the SI) unit of force in 1948. A small apple, fittingly, exerts a gravitational force of about 1N on Earth. Force
ohmOhm[Omega]electric_resistance1.0ohm Named after Georg Ohm, the German physicist who discovered Ohm's Law; since 1990, the unit has been internationally maintained using the Quantum Hall Effect and a conventional value for the von Klitzing constant. Resistance, reactance, impedance
pa.sPascal secondPa.s = N.s.m-2dynamic_viscosity1.0pa.s not yet added Dynamic Viscosity
pascalPascalPapressure1.0pascal The pascal, named after Blaise Pascal, is also used to measure stress, Young's modulus, and tensile strength. For atmospheric pressures, however, it is commonly regarded as an inconveniently small unit. Pressure
rad.s-1radian per secondrad.s-1angular_velocity1.0rad.s-1 not yet added Angular velocity
radiannullradangle1.0radian The radian is therefore formally dimensionless, as it is a ratio of two lengths. There are 2*pi radians in a complete circle. angle
ssecondstime1.0s The second has had many definitions throughout history; originally, it was one sixtieth of one twenty-fourth of a solar day (the factor of sixty coming from Babylonian counting and the factor of 24 from Ancient Egypt). The present definition dates from the Thirteenth General Conference on Weights and Measures, which took place in 1967. Time
s.m-1siemens per metreS.m-1electrical_conductivity1.0s.m-1 not yet added Electrical conductivity
s.m2.mol-1siemens square metre per moleS.m2.mol-1molar_conductivity1.0s.m2.mol-1 not yet added molar conductivity
siemensSiemensSelectric_conductance1.0siemens This is equivalent to the obsolete "mho" unit (derived from spelling "ohm" backwards and written with an upside-down capital omega). Electric conductance
sievertSievertSvradioactive_equivalent_dose1.0sievert The sievert attempts to reflect the biological effects of radiation as opposed to the physical aspects, which are characterised by the absorbed dose, measured in grays. Note that these are the same units as the sievert. To avoid any risk of confusion between the absorbed dose and the equivalent dose, one must use the corresponding special units, namely the gray instead of the joule per kilogram for absorbed dose and the sievert instead of the joule per kilogram for the dose equivalent. equivalent dose (of ionising radiation)
steradiansteradiansrsolid_angle1.0steradian Since the surface area of a sphere is 4*pi*r^2, a sphere measures 4*pi steradians. The steradian is the solid analogue of the radian, and like that unit, is formally dimensionless (in this case, being the ratio of two areas.) solid_angle
teslaTeslaTmagnetic_flux_density1.0tesla The tesla is the value of the total magnetic flux (in some sense, the "power" of a magnet) over area; hence reducing the affected area generally increases the magnetic flux density. Like many of the other electromagnetic units, one tesla is very large. Magnetic flux density, magnetic inductivity
v.m-1volt per metreV.m-1electric_field_strength1.0v.m-1 not yet added Electric field strength
voltVoltVelectric_potential_difference1.0volt The number of volts is a measure of the strength of an electrical source in the sense of how much power is produced for a given current level. It is named in honor of Alessandro Volta (1745–1827), who invented the voltaic pile, the first chemical battery. Since 1990 the volt is maintained internationally for practical measurement using the Josephson effect. Electrical potential difference, Electromotive force
w.m-1.k-1watt per metre kelvinW.m-1.K-1thermal_conductivity1.0w.m-1.k-1 not yet added Thermal conductivity
w.m-2watt per square metreW.m-2heat_flux_density1.0w.m-2 not yet added heat flux density
wattWattWpower1.0watt The watt dates back to the Second Congress of the British Association of the Advancement of Science in 1889, and is named after James Watt, one of the key engineers to the development of the steam engine. Power
weberWeberWbmagnetic_flux1.0weber The weber, like the farad, is a very large unit. Magnetic flux