Metric units are
units
Unit may refer to:
Arts and entertainment
* UNIT, a fictional military organization in the science fiction television series ''Doctor Who''
* Unit of action, a discrete piece of action (or beat) in a theatrical presentation
Music
* Unit (album), ...
based on the metre, gram or second and decimal (power of ten) multiples or sub-multiples of these. The most widely used examples are the units of the
International System of Units (SI). By extension they include units of
electromagnetism
In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of ...
from the
CGS and SI units systems, and other units for which use of
SI prefixes has become the norm. Other unit systems using metric units include:
*
International System of Electrical and Magnetic Units The International System of Electrical and Magnetic Units is an obsolete system of units used for measuring electrical and magnetic quantities. It was proposed as a system of practical international units by unanimous recommendation at the Internati ...
*
Metre–tonne–second (MTS) system of units
*
MKS system of units (metre, kilogram, second)
Metric units that are part of the SI
The first group of metric units are those that are at present defined as units within the International System of Units (SI). In its most restrictive interpretation, this is what may be meant when the term ''metric unit'' is used.
The SI defines 30 named units and associated symbols:
* The unit
one (1) is the unit of a
quantity of dimension one.
* The
second (s) is the unit of
time
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, ...
.
* The
metre
The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefi ...
(m) is the unit of
length.
* The
kilogram (kg) is the unit of
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
.
* The
ampere (A) is the unit of
electric current.
* The
kelvin
The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phy ...
(K) is the unit of
thermodynamic temperature
Thermodynamic temperature is a quantity defined in thermodynamics as distinct from kinetic theory or statistical mechanics.
Historically, thermodynamic temperature was defined by Kelvin in terms of a macroscopic relation between thermodynamic ...
.
* The
mole
Mole (or Molé) may refer to:
Animals
* Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America
* Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpida ...
(mol) is the unit of
amount of substance.
* The
candela
The candela ( or ; symbol: cd) is the unit of luminous intensity in the International System of Units (SI). It measures luminous power per unit solid angle emitted by a light source in a particular direction. Luminous intensity is analogous t ...
(cd) is the unit of
luminous intensity
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human e ...
.
* The
hertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that o ...
(Hz) is equal to one
reciprocal second
The inverse second or reciprocal second (s−1) is a unit of frequency, defined as the multiplicative inverse of the second (a unit of time). It is dimensionally equivalent to:
* the unit hertz – the SI unit for frequency
* the unit radian per s ...
().
* The
radian
The radian, denoted by the symbol rad, is the unit of angle in the International System of Units (SI) and is the standard unit of angular measure used in many areas of mathematics. The unit was formerly an SI supplementary unit (before tha ...
(rad) is equal to one ().
* The
steradian
The steradian (symbol: sr) or square radian is the unit of solid angle in the International System of Units (SI). It is used in three-dimensional geometry, and is analogous to the radian, which quantifies planar angles. Whereas an angle in radian ...
(sr) is equal to one ().
* The
newton (N) is equal to one kilogram-metre per second squared ().
* The
pascal (Pa) is equal to one newton per square metre ().
* The
joule
The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applie ...
(J) is equal to one newton-metre ().
* The
watt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...
(W) is equal to one joule per second ().
* The
coulomb (C) is equal to one ampere second ().
* The
volt
The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827).
Defin ...
(V) is equal to one joule per coulomb ().
* The
weber (Wb) is equal to one volt-second ().
* The
tesla (T) is equal to one weber per square metre ().
* The
farad (F) is equal to one coulomb per volt ().
* The
ohm (Ω) is equal to one volt per ampere ().
* The
siemens (S) is equal to one ampere per volt ().
* The
henry
Henry may refer to:
People
*Henry (given name)
* Henry (surname)
* Henry Lau, Canadian singer and musician who performs under the mononym Henry
Royalty
* Portuguese royalty
** King-Cardinal Henry, King of Portugal
** Henry, Count of Portugal, ...
(H) is equal to one volt-second per ampere ().
* The
degree Celsius
Degree may refer to:
As a unit of measurement
* Degree (angle), a unit of angle measurement
** Degree of geographical latitude
** Degree of geographical longitude
* Degree symbol (°), a notation used in science, engineering, and mathematics
...
(°C) is equal to one kelvin ().
* The
lumen (lm) is equal to one candela-steradian ().
* The
lux (lx) is equal to one lumen per square metre ().
* The
becquerel
The becquerel (; symbol: Bq) is the unit of radioactivity in the International System of Units (SI). One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. For applications relatin ...
(Bq) is equal to one
reciprocal second
The inverse second or reciprocal second (s−1) is a unit of frequency, defined as the multiplicative inverse of the second (a unit of time). It is dimensionally equivalent to:
* the unit hertz – the SI unit for frequency
* the unit radian per s ...
().
* The
gray
Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...
(Gy) is equal to one joule per kilogram ().
* The
sievert
The sievert (symbol: SvNot be confused with the sverdrup or the svedberg, two non-SI units that sometimes use the same symbol.) is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing rad ...
(Sv) is equal to one joule per kilogram ().
* The
katal
The katal (symbol: kat) is the unit of catalytic activity in the International System of Units (SI) used for quantifying the catalytic activity of enzymes (that is, measuring the enzymatic activity level in enzyme catalysis) and other catalyst ...
(kat) is equal to one mole per second ().
There are twenty-four
metric prefix
A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The pr ...
es that can be combined with any of these units except one (1) and kilogram (kg) to form further units of the SI. For mass, the same prefixes are applied to the gram (g) instead of the kilogram.
Metric units that are not part of the SI
There are several metric systems, most of which have become disused or are still used in only niche disciplines. Systems are listed with named units that are associated with them.
CGS
The
centimetre–gram–second system of units
The centimetre–gram–second system of units (abbreviated CGS or cgs) is a variant of the metric system based on the centimetre as the unit of length, the gram as the unit of mass, and the second as the unit of time. All CGS mechanical units ...
(CGS) is based on three base units: centimetre, gram and second. Its subsystems (
CGS-ESU,
CGS-EMU and
CGS-Gaussian) have different defining equations for their systems of quantities for defining electromagnetic quantities and hence the associated units, with CGS-Gaussian units being selected from each of the other two subsystems.
The CGS-to-SI correspondence of electromagnetic units as given was exact prior to the
2019 redefinition of the SI base units
In 2019, four of the seven SI base units specified in the International System of Quantities were redefined in terms of natural physical constants, rather than human artifacts such as the standard kilogram.
Effective 20 May 2019, the 144th ...
, until which the
magnetic constant ''μ''
0 was defined as . As from the redefinition, ''μ''
0 has an inexactly known value when expressed in SI units, with the exactness of the electromagnetic unit correspondence given here being affected accordingly.
CGS nonelectromagnetic units
* The
kayser (K) is a unit of
wavenumber equal to ().
* The
gal (Gal) is a unit of
acceleration
In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by t ...
equal to .
* The
dyne
The dyne (symbol: dyn; ) is a derived unit of force specified in the centimetre–gram–second (CGS) system of units, a predecessor of the modern SI.
History
The name dyne was first proposed as a CGS unit of force in 1873 by a Committee of ...
(dyn) is a unit of
force equal to ().
* The
barye (Ba) is a unit of
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
equal to ().
* The
erg (erg) is a unit of
energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...
equal to ().
* The
poise (P) is a unit of
dynamic viscosity equal to ().
* The
stokes (St) is a unit of
kinematic viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the int ...
equal to ().
* The
stilb (sb) is a unit of
luminance equal to ().
* The
phot (ph) is a unit of
illuminance
In photometry (optics), photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate w ...
equal to ().
* The
rayl is a unit of
specific acoustic impedance, equal to 1 dyn⋅s⋅cm
−3.
CGS-ESU electromagnetic units
* The
statwatt (statW) is a unit of
power
Power most often refers to:
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power
* Power (social and political), the ability to influence people or events
** Abusive power
Power may a ...
equal to , which is equal to .
* The
statcoulomb
The franklin (Fr) or statcoulomb (statC) electrostatic unit of charge (esu) is the physical unit for electrical charge used in the cgs-esu and Gaussian units. It is a derived unit given by
: 1 statC = 1 dyn1/2⋅cm = 1 cm3/2⋅g1/2⋅s−1.
Tha ...
(statC) or
franklin (Fr) is a unit of
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
equal to , corresponding to ~.
* The
statampere (statA) is a unit of
electric current equal to , corresponding to ~.
* The
statvolt (statV) is a unit of
electric potential difference equal to , corresponding to .
* The
statohm is a unit of
electric resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels ...
equal to , corresponding to ~.
* The
statsiemens or
statmho is a unit of
electric conductance equal to , corresponding to ~.
* The
stathenry is a unit of
electric inductance equal to , corresponding to ~.
* The
statfarad (statF) is a unit of
electric capacitance equal to , corresponding to ~.
* The statdaraf (statD) is a unit of
electric elastance equal to 1/statF.
* The
statweber is a unit of
magnetic flux, corresponding to .
* The
stattesla is a unit of
magnetic flux density
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
equal to , corresponding to .
CGS-EMU electromagnetic units
* The
abwatt (abW) is a unit of
power
Power most often refers to:
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power
* Power (social and political), the ability to influence people or events
** Abusive power
Power may a ...
equal to , which is equal to .
* The
abcoulomb
The abcoulomb (abC or aC) or electromagnetic unit of charge (emu of charge) is the derived physical unit of electric charge in the cgs-emu system of units. One abcoulomb is equal to ten coulombs.
The name "abcoulomb" was introduced by Kennelly ...
(abC) is a unit of
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
equal to , corresponding to .
* The
abampere (abA) or
biot (Bi) is a unit of
electric current, corresponding to .
* The
abvolt
The abvolt (abV) is the unit of potential difference in the CGS-EMU system of units. It corresponds to in the SI system and 1/ statvolt ≈ in the CGS-ESU system.
A potential difference of 1 abV will drive a current of one abampere through ...
(abV) is a unit of
electric potential difference, corresponding to .
* The
abohm
The abohm is the derived unit of electrical resistance in the emu-cgs ''(centimeter-gram-second)'' system of units (emu stands for "electromagnetic units"). One abohm corresponds to 10−9 ohms in the SI system of units, which is a nanoohm. ...
(abΩ) is a unit of
electric resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels ...
, corresponding to .
* The
abmho is a unit of
electric conductance, corresponding to .
* The
abhenry is a unit of
electric inductance, corresponding to .
* The
abfarad (abF) is a unit of
electric capacitance, corresponding to .
* The
gilbert (Gb) is a unit of
magnetomotive force
In physics, the magnetomotive force (mmf) is a quantity appearing in the equation for the magnetic flux in a magnetic circuit, often called Ohm's law for magnetic circuits. It is the property of certain substances or phenomena that give rise to ...
equal to one biot-turn, corresponding to (10/4π) A = .
* The
oersted
The oersted (symbol Oe) is the coherent derived unit of the auxiliary magnetic field H in the centimetre–gram–second system of units (CGS). It is equivalent to 1 dyne per maxwell.
Difference between CGS and SI systems
In the CGS system, ...
(Oe) is a unit of
magnetic field strength equal to , corresponding to (1000/4π) A/m = .
* The
maxwell (Mx) is a unit of
magnetic flux, corresponding to .
* The
gauss
Johann Carl Friedrich Gauss (; german: Gauß ; la, Carolus Fridericus Gauss; 30 April 177723 February 1855) was a German mathematician and physicist who made significant contributions to many fields in mathematics and science. Sometimes refer ...
(G) is a unit of
magnetic flux density
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
, corresponding to .
CGS-Gaussian electromagnetic units
* The
franklin (Fr) is a unit of
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
equal to , corresponding to ~.
* The
oersted
The oersted (symbol Oe) is the coherent derived unit of the auxiliary magnetic field H in the centimetre–gram–second system of units (CGS). It is equivalent to 1 dyne per maxwell.
Difference between CGS and SI systems
In the CGS system, ...
(Oe) is a unit of
magnetic field strength equal to , corresponding to ~.
* The
maxwell (Mx) is a unit of
magnetic flux, corresponding to .
* The
gauss
Johann Carl Friedrich Gauss (; german: Gauß ; la, Carolus Fridericus Gauss; 30 April 177723 February 1855) was a German mathematician and physicist who made significant contributions to many fields in mathematics and science. Sometimes refer ...
(G) is a unit of
magnetic flux density
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
, corresponding to .
MTS
* The
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
(t) is a unit of
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
equal to .
* The
sthène
The sthène (; symbol sn), sometimes spelled (or misspelled) sthéne or sthene (from grc, σθένος, sthénos, force), is an obsolete unit of force (physics), force or thrust in the metre–tonne–second system of units (mts) introduced in Fra ...
(sn) is a unit of
force equal to .
* The
pièze (pz) is a unit of
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
equal to .
MKSA
* The
cycle per second
The cycle per second is a once-common English name for the unit of frequency now known as the hertz (Hz). The plural form was typically used, often written cycles per second, cycles/second, c.p.s., c/s, or, ambiguously, just cycles (Cy./Cyc.). The ...
(cps or cyc/s) is a unit of
frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
equal to .
* The MKS
rayl is a unit of
acoustic impedance
Acoustic impedance and specific acoustic impedance are measures of the opposition that a system presents to the acoustic flow resulting from an acoustic pressure applied to the system. The SI unit of acoustic impedance is the pascal-second per cu ...
equal to .
* The
mho (℧) is a unit of
electric conductance equal to .
MKpS units
* The
kilogram-force
The kilogram-force (kgf or kgF), or kilopond (kp, from la, pondus, lit=weight), is a non-standard gravitational metric unit of force. It does not comply with the International System of Units (SI) and is deprecated for most uses. The kilogram- ...
(kgf), also
kilopond (kp), is a unit of
force ().
* The
hyl is a unit of
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
equal to ().
* The
poncelet
The poncelet (symbol p) is an obsolete unit of power, once used in France and replaced by (ch, metric horsepower). The unit was named after Jean-Victor Poncelet.François Cardarelli, ''Encyclopaedia of Scientific Units, Weights and Measures: The ...
(p) is a unit of
power
Power most often refers to:
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power
* Power (social and political), the ability to influence people or events
** Abusive power
Power may a ...
equal to ().
* The
technical atmosphere
Technical may refer to:
* Technical (vehicle), an improvised fighting vehicle
* Technical analysis, a discipline for forecasting the future direction of prices through the study of past market data
* Technical drawing, showing how something is co ...
(at) is a (non-coherent) unit of
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
equal to ().
Other metric units
Length
* The
fermi is a unit of distance used in
nuclear physics
Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter.
Nuclear physics should not be confused with atomic physics, which studies the ...
equal to .
* The
angstrom
The angstromEntry "angstrom" in the Oxford online dictionary. Retrieved on 2019-03-02 from https://en.oxforddictionaries.com/definition/angstrom.Entry "angstrom" in the Merriam-Webster online dictionary. Retrieved on 2019-03-02 from https://www.m ...
(symbol Å) is a unit of distance used in
chemistry and
atomic physics equal to .
* The
micron
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Un ...
(μ) is a unit of distance equal to one
micrometre
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...
().
* The
basic module (M) is a unit of distance equal to one hundred millimetres ().
* The
myriametre (mym) is a unit of distance equal to ten kilometres ().
* The
hebdometre
Hebdo- (symbol H) is an obsolete decimal metric prefix equal to 107. It is derived from the Greek ''hebdοmos'' ( el, ἕβδομος) meaning ''seventh''.
The definition of one ''hebdomometre'' or ''hebdometre'' as was originally proposed by R ...
is a unit of distance equal to ten megametres ().
* The
spat (S) is a unit of distance equal to one
terametre ().
Area
* The
shed is a unit of area used in nuclear physics equal to 10
−24 barn
A barn is an agricultural building usually on farms and used for various purposes. In North America, a barn refers to structures that house livestock, including cattle and horses, as well as equipment and fodder, and often grain.Alle ...
s (100 rm
2 = 10
−52 m
2).
* The
outhouse
An outhouse is a small structure, separate from a main building, which covers a toilet. This is typically either a pit latrine or a bucket toilet, but other forms of dry (non-flushing) toilets may be encountered. The term may also be used ...
is a unit of area used in nuclear physics equal to 10
−6 barns (100 am
2 = 10
−34 m
2).
* The
barn
A barn is an agricultural building usually on farms and used for various purposes. In North America, a barn refers to structures that house livestock, including cattle and horses, as well as equipment and fodder, and often grain.Alle ...
(b) is a unit of area used in nuclear physics equal to one hundred femtometres squared (100 fm
2 = 10
−28 m
2).
* The
are (a) is a unit of area equal to .
* The
decare
The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is a ...
(daa) is a unit of area equal to .
* The
hectare
The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100- metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is ...
(ha) is a unit of area equal to .
Volume
* The
lambda
Lambda (}, ''lám(b)da'') is the 11th letter of the Greek alphabet, representing the voiced alveolar lateral approximant . In the system of Greek numerals, lambda has a value of 30. Lambda is derived from the Phoenician Lamed . Lambda gave ri ...
(λ) is a unit of volume equal to one cubic
millimetre (1 mm
3).
* The
litre
The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3 ...
(symbol l or L) is a unit of volume equal to one cubic
decimetre
The decimetre (symbol dm) or decimeter (American English) is a unit of length in the International System of Units (SI), equal to one tenth of a metre, ten centimetres, 100 millimetres or 3.937 inches.
The common non-SI metric unit of volume, ...
(1 dm
3).
* The
stere (st) is a unit of volume equal to .
Reciprocal length
* The
dioptre is a unit of
optical power
In optics, optical power (also referred to as dioptric power, refractive power, focusing power, or convergence power) is the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the reciprocal of the ...
equal to one
reciprocal metre Reciprocal length or inverse length is a quantity or measurement used in several branches of science and mathematics. As the reciprocal of length, common units used for this measurement include the reciprocal metre or inverse metre (symbol: m− ...
().
Time
* The
svedberg
A Svedberg unit or svedberg (symbol S, sometimes Sv) is a non- SI metric unit for sedimentation coefficients. The Svedberg unit offers a measure of a particle's size indirectly based on its sedimentation rate under acceleration (i.e. how fast a ...
(S or Sv) is a unit of time used in chemistry equal to one hundred
femtoseconds ().
* The
shake is a unit of time used in nuclear physics equal to ten
nanosecond
A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds.
The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ( ...
s ().
* The
sigma is a unit of time equal to one
microsecond
A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.
A microsecond is equal to 1000 ...
().
* The
jiffy is sometimes used to mean a unit of time of .
Reciprocal time
* The
fresnel
Augustin-Jean Fresnel (10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Newton's corpuscular the ...
is a unit of
frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
equal to .
Reciprocal time squared
* The
eotvos (E) is a unit of
gravitational gradient
Gravity gradiometry is the study and measurement of variations ( anomalies) in the Earth's gravity field. The gravity gradient tensor is the spatial rate of change of gravitational acceleration; as acceleration is a vector quantity, with magnitu ...
equal to ().
Speed
* The
benz is a unit of
speed
In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude
Magnitude may refer to:
Mathematics
*Euclidean vector, a quantity defined by both its magnitude and its direction
*Magnitude (ma ...
equal to one metre per second (1 m/s).
Acceleration
* The leo is a unit of acceleration equal to .
Flow rate
* The
sverdrup
In oceanography, the sverdrup (symbol: Sv) is a non- SI metric unit of volumetric flow rate, with equal to . It is equivalent to the SI derived unit cubic hectometer per second (symbol: hm3/s or hm3⋅s−1): 1 Sv is equal to 1 hm3/s. It is u ...
(Sv) is a unit of volume flow rate equal to one million metres cubed per second (10
6 m
3/s).
Aldersey-Williams, 2016
/ref>
Mass
* The undecimogramme is a unit of mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
equal to ten picograms (10 pg).
* The gamma (γ) is a unit of mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
equal to one microgram (1 μg).
* The gravet is a unit of mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
equal to one gram (1 g).
* The grave
A grave is a location where a dead body (typically that of a human, although sometimes that of an animal) is buried or interred after a funeral. Graves are usually located in special areas set aside for the purpose of burial, such as grav ...
is a unit of mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
equal to one kilogram (1 kg).
* The bar is a unit of mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
equal to one megagram (1 Mg).
Linear mass density
* The tex
Tex may refer to:
People and fictional characters
* Tex (nickname), a list of people and fictional characters with the nickname
* Joe Tex (1933–1982), stage name of American soul singer Joseph Arrington Jr.
Entertainment
* ''Tex'', the Italian ...
(tex) is a unit of linear mass density equal to one gram per kilometre (1 g/km).
* The number metric (Nm) is equal to 1000 metres per kilogram (1 km/kg).
Pressure
* The metre sea water
The metre (or meter) sea water (msw) is a metric unit of pressure used in underwater diving. It is defined as one tenth of a bar.
The unit used in the US is the foot sea water (fsw), based on standard gravity and a sea-water density of 64&nb ...
(msw) is a unit of pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
defined as 0.1 bar, which is equal to .
* The bar (bar) is a unit of pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
equal to .
Energy
* The foe is a unit of energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...
equal to ().
Viscosity
* The poiseuille is a unit of dynamic viscosity equal to one pascal-second ().
Electrical
* The Siemens mercury unit is a unit of electric resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels ...
, corresponding to ~.
* The gamma (γ) a unit of magnetic flux density
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
, corresponding to .
* The debye
The debye (symbol: D) (; ) is a CGS unit (a non- SI metric unit) of electric dipole momentTwo equal and opposite charges separated by some distance constitute an electric dipole. This dipole possesses an electric dipole moment whose value is g ...
(D) is a unit of electric dipole moment equal to , corresponding to ~.
* The buckingham (B) is a unit of electric quadrupole moment
A quadrupole or quadrapole is one of a sequence of configurations of things like electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure ref ...
equal to .
Electromagnetic radiation
* The jansky
The jansky (symbol Jy, plural ''janskys'') is a non- SI unit of spectral flux density, or spectral irradiance, used especially in radio astronomy. It is equivalent to 10−26 watts per square metre per hertz.
The ''flux density'' or ''monoch ...
(Jy) is a unit of spectral irradiance In radiometry, irradiance is the radiant flux ''received'' by a ''surface'' per unit area. The SI unit of irradiance is the watt per square metre (W⋅m−2). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used ...
equal to 10−26 W⋅m−2⋅Hz−1 ().
* The solar flux unit is a unit of spectral irradiance In radiometry, irradiance is the radiant flux ''received'' by a ''surface'' per unit area. The SI unit of irradiance is the watt per square metre (W⋅m−2). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used ...
equal to 10−22 W⋅m−2⋅Hz−1 ().
* The nox
In atmospheric chemistry, is shorthand for nitric oxide () and nitrogen dioxide (), the nitrogen oxides that are most relevant for air pollution.
These gases contribute to the formation of smog and acid rain, as well as affecting tropo ...
(nx) is a unit of illuminance
In photometry (optics), photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate w ...
equal to 1 millilux ().
* The nit (nt) is a unit of luminance equal to one candela
The candela ( or ; symbol: cd) is the unit of luminous intensity in the International System of Units (SI). It measures luminous power per unit solid angle emitted by a light source in a particular direction. Luminous intensity is analogous t ...
per metre squared ().
* The lambert (L) is a unit of luminance equal to 104/π cd⋅m−2.
* The lumerg is a unit of luminous energy
In photometry, luminous energy is the perceived energy of light. This is sometimes called the quantity of light.[talbot
Talbot was an automobile marque introduced in 1902 by English-French company Clément-Talbot. The founders, Charles Chetwynd-Talbot, 20th Earl of Shrewsbury and Adolphe Clément-Bayard, reduced their financial interests in their Clément-Talbot ...](_blank)
(T) is a unit of luminous energy
In photometry, luminous energy is the perceived energy of light. This is sometimes called the quantity of light.[einstein
Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...](_blank)
(E) is a unit of amount
Quantity or amount is a property that can exist as a multitude or magnitude, which illustrate discontinuity and continuity. Quantities can be compared in terms of "more", "less", or "equal", or by assigning a numerical value multiple of a unit ...
of photon
A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...
s, equal to one mole
Mole (or Molé) may refer to:
Animals
* Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America
* Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpida ...
(1 mol) of photons.
* The rayleigh (R) is a unit of photon flux rate density equal to 1010 m−2⋅s−1 (104 mm−2⋅s−1).
Radioactivity
* The rad
RAD or Rad may refer to:
People
* Robert Anthony Rad Dougall (born 1951), South African former racing driver
* Rad Hourani, Canadian fashion designer and artist
* Nickname of Leonardus Rad Kortenhorst (1886–1963), Dutch politician
* Radley R ...
(rad) is a unit of absorbed dose
Absorbed dose is a dose quantity which is the measure of the energy deposited in matter by ionizing radiation per unit mass. Absorbed dose is used in the calculation of dose uptake in living tissue in both radiation protection (reduction of harmf ...
equal to .
* The roentgen equivalent man (rem) is a unit of equivalent dose
Equivalent dose is a dose quantity '' H '' representing the stochastic health effects of low levels of ionizing radiation on the human body which represents the probability of radiation-induced cancer and genetic damage. It is derived from the ...
equal to .
* The rutherford (Rd) is a unit of radioactivity defined as one million decays per second ().
Concentration
* The molar (M) is equal to one mole per litre ().
Nonmetric units
Hybrid units
Some nonmetric units arose as a combination of a nonmetric quantity combined with a metric unit. Examples include:
Metric unit combined with a unit permitted alongside the SI
* The ampere hour
An ampere hour or amp hour (symbol: A⋅h or A h; often simplified as Ah) is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for on ...
is a unit of electric charge equal to .
* The watt hour
A kilowatt-hour ( unit symbol: kW⋅h or kW h; commonly written as kWh) is a unit of energy: one kilowatt of power for one hour. In terms of SI derived units with special names, it equals 3.6 megajoules (MJ). Kilowatt-hours are a common bi ...
(W⋅h) is equal to .
* The watt hour per day (W⋅h/d) is a unit of power equal to 3.6 kJ/(24 h) = 1/24 W.
* The enzyme unit The enzyme unit, or international unit for enzyme (symbol U, sometimes also IU) is a unit of enzyme's catalytic activity.
1 U (μmol/min) is defined as the amount of the enzyme that catalyzes the conversion of one micromole of substrate per min ...
(U) is equal to one micromole per minute (50/3 nkat).
Other combinations
* The normal litre per minute (NLPM) is approximately equal to (0.001/60) m3/s.
* The standard litre per minute
The standard liter per minute (SLM or SLPM) is a unit of volumetric flow rate of a gas at standard conditions for temperature and pressure (STP), which is most commonly practiced in the United States, whereas European practice revolves around th ...
(SLPM) is approximately equal to (0.001/60) m3/s.
* The centimetre of water
A centimetre or millimetre of water (US spelling ''centimeter'' or ''millimeter of water'') are less commonly used measures of pressure derived from pressure head.
Centimetre of water
A ''centimetre of water'' (US spelling ''centimeter of water ...
(cmH2O) is approximately .
* The millimetre of mercury
A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high, and currently defined as exactly pascals. It is denoted mmHg or mm Hg.
Although not an ...
(mmHg) is approximately .
* The torr
The torr (symbol: Torr) is a unit of pressure based on an absolute scale, defined as exactly of a standard atmosphere (). Thus one torr is exactly (≈ ).
Historically, one torr was intended to be the same as one "millimeter of mercury ...
(Torr) is approximately 133.3224 pascals.
* The centimetre of mercury (cmHg) is approximately .
* The electronvolt
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defi ...
(eV) is equal to = .
* The calorie
The calorie is a unit of energy. For historical reasons, two main definitions of "calorie" are in wide use. The large calorie, food calorie, or kilogram calorie was originally defined as the amount of heat needed to raise the temperature of on ...
(cal) is .
* The langley Langley may refer to:
People
* Langley (surname), a common English surname, including a list of notable people with the name
* Dawn Langley Simmons (1922–2000), English author and biographer
* Elizabeth Langley (born 1933), Canadian perfor ...
(Ly) is a unit of energy density equal to 1 calorie per square centimetre ().
* The darcy (d) is a unit of permeability approximately equal to ().
Traditional units standardized in terms of metric units
Further traditional units were standardized by defining them in terms of metric units, such as the imperial inch
Measuring tape with inches
The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelfth") ...
, almost always retaining their original name, and replaced the units as traditionally defined.
Nonmetric units that arose as approximations to traditional units that were adjusted for convenient conversion to metric units were typically named as for the traditional unit but qualified with the word "metric". The corresponding original traditional usually remained in use alongside the corresponding "metric" version.
Units equal to an SI unit multiplied by an integer power of 10, and multiplied or divided by 1, 2, 3 or 4
* The neper (Np) is a unit of logarithmic ratio equal to 1.
* The percent (%) is equal to one part in a hundred (0.01).
* The permille
Per mille (from New Latin, Latin , "in each thousand") is an expression that means parts per thousand. Other recognised spellings include per mil, per mill, permil, permill, or permille.
The associated sign is written , which looks like a ...
(‰) is equal to one part in a thousand (0.001).
* The permyriad
A basis point (often abbreviated as bp, often pronounced as "bip" or "beep") is one hundredth of 1 percentage point. The related term '' permyriad'' means one hundredth of 1 percent. Changes of interest rates are often stated in basis points. If ...
(‱) is equal to one part in ten thousand ().
* The part per million
In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they ...
(ppm) is equal to one part in a million ().
* The part per billion
In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they ...
(ppb) is equal to one part in a billion ().
* The part per trillion
In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantity, dimensionless quantities, e.g. mole fraction or mass fraction (chemistry), mass fraction. Since these f ...
(ppt) is equal to one part in a trillion ().
* The part per quadrillion (ppq) is equal to one part in a quadrillion ().
* The metric inch
Metric units are units based on the metre, gram or second and decimal (power of ten) multiples or sub-multiples of these. The most widely used examples are the units of the International System of Units (SI). By extension they include units of e ...
is equal to twenty five millimetres ().
* The cun is equal to one tenth of a chi
Chi or CHI may refer to:
Greek
*Chi (letter), the Greek letter (uppercase Χ, lowercase χ);
Chinese
*Chi (length), ''Chi'' (length) (尺), a traditional unit of length, about ⅓ meter
*Chi (mythology) (螭), a dragon
*Chi (surname) (池, pin ...
(approximately 33.3333 mm).
* The metric foot
ISO 2848 (''Building construction – Modular coordination – Principles and rules)'' is an international standard for the construction industry that describes the aims of modular coordination and gives the rules to be used in establishing the di ...
is equal to three hundred millimetres ().
* The chi is equal to one third of a metre (approximately 333.333 mm).
* The metric lieue is equal to four kilometres ().
* The Scandinavian mile
A Scandinavian mile (Norwegian and sv, mil, [], like "meal") is a unit of length common in Norway and Sweden, but not Denmark. Today, it is standardised as 1 being , but it had different values in the past.
The word is derived from the same ...
(''mil'') is equal to ten kilometres ().
* The metric dunam is equal to one thousand metres squared ().
* The stremma
The stremma ( stremmata; el, στρέμμα, ''strémma'') is a Greek unit of land area equal to 1,000 square metres. Historically, stremmata were not standardized, and may have been anywhere from .
History
The Ancient Greece, ancient Greek Greek ...
is equal to one thousand metres squared (1000 m2).
* The '' food labeling ounce'' is equal to 30 cm3.
* The metric cup
The cup is a cooking measure of volume, commonly associated with cooking and serving sizes. In the US, it is traditionally equal to . Because actual drinking cups may differ greatly from the size of this unit, standard measuring cups may be use ...
is equal to .
* The metric carat (ct) is equal to .
* The li is equal to one ten-thousandth of a jin (50 mg).
* The fen
A fen is a type of peat-accumulating wetland fed by mineral-rich Groundwater, ground or surface water. It is one of the main types of wetlands along with marshes, swamps, and bogs. Bogs and fens, both peat-forming ecosystems, are also known as ...
is equal to one thousandth of a jin (500 mg).
* The qian is equal to one hundredth of a jin (5 g).
* The liang (or tael) is equal to one tenth of a jin (50 g).
* The metric pound is equal to .
* The jin (or catty) is equal to 500 g.
* The dan
Dan or DAN may refer to:
People
* Dan (name), including a list of people with the name
** Dan (king), several kings of Denmark
* Dan people, an ethnic group located in West Africa
**Dan language, a Mande language spoken primarily in Côte d'Ivoi ...
is equal to one hundred jin (50 kg).
* The metric quintal (q) is equal to one hundred kilograms ().
* The donkey power is equal to 250 W.
Other units
* The mo is equal to one ten-thousandth of a shaku Shaku may refer to:
* Shaku (unit)
* Shaku (ritual baton)
* Buddhist surname
In East Asian Buddhism, monks and nuns usually adopt a Buddhist surname and a Dharma name, which are combined in the surname-first East-Asian naming order. Since the 4th c ...
(approximately 0.0303030 mm).
* The rin is equal to one thousandth of a shaku (approximately 0.303030 mm).
* The bu is equal to one hundredth of a shaku (approximately 3.03030 mm).
* The sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
is equal to one tenth of a shaku (approximately 30.3030 mm).
* The shaku Shaku may refer to:
* Shaku (unit)
* Shaku (ritual baton)
* Buddhist surname
In East Asian Buddhism, monks and nuns usually adopt a Buddhist surname and a Dharma name, which are combined in the surname-first East-Asian naming order. Since the 4th c ...
is equal to 10/33 m (approximately 303.030 mm).
* The jo is equal to ten shaku (approximately 3030.30 mm).
* The metric mile is equal to .
* The tsubo
A ''pyeong'' (abbreviationpy) is a Korean unit of area and floorspace, equal to a square '' kan'' or 36square Korean feet. The ''ping'' and ''tsubo'' are its equivalent Taiwanese and Japanese units, similarly based on a square '' bu'' ( ja:步) ...
is equal to 400/121 metres squared (approximately 3.306 m2).
* The sho
Sho, Shō or SHO may refer to:
Music
* ''Shō'' (instrument) (笙), a Japanese wind instrument
* ''Kane'' (instrument) (鉦), a Japanese percussion instrument
* Sho?, a Dubai rock band
People
* Shō (given name), including ''Sho''
* Shō (su ...
is equal to 2401/1331 litres (approximately 1.804 dm3).
* The hyakume is equal to one tenth of a kan (375 g).
* The kan is equal to 15/4 kilograms (3.75 kg).
* The metric horsepower
Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are the ...
is equal to (approximately 735.499 W).
See also
* Electrostatic units The electrostatic system of units (CGS-ESU) is a system of units used to measure quantities of electric charge, electric current, and voltage within the centimetre–gram–second (or "CGS") system of metric units. In electrostatic units, electric ...
* Gaussian units
Gaussian units constitute a metric system of physical units. This system is the most common of the several electromagnetic unit systems based on cgs (centimetre–gram–second) units. It is also called the Gaussian unit system, Gaussian-cgs uni ...
* Gravitational metric system
The gravitational metric system (original French term ) is a non-standard system of units, which does not comply with the International System of Units (SI). It is built on the three base quantity, base quantities length, time and force with base u ...
* History of the metric system
The history of the metric system began during the Age of Enlightenment with measures of length and weight derived from nature, along with their decimal multiples and fractions. The system became the standard of France and Europe within half a ...
* Metric system
The metric system is a system of measurement that succeeded the Decimal, decimalised system based on the metre that had been introduced in French Revolution, France in the 1790s. The historical development of these systems culminated in the d ...
* Outline of the metric system
The following outline is provided as an overview of and topical guide to the metric system – various loosely related systems of measurement that trace their origin to the decimal system of measurement introduced in France during the Frenc ...
* RKM code
The RKM code, also referred to as "letter and numeral code for resistance and capacitance values and tolerances", "letter and digit code for resistance and capacitance values and tolerances", or informally as "R notation" is a notation to specif ...
* Unified Code for Units of Measure The Unified Code for Units of Measure (UCUM) is a system of codes for unambiguously representing measurement units. Its primary purpose is machine-to-machine communication rather than communication between humans.
The code set includes all units de ...
Notes
References
{{Reflist
Metric system