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
The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...
(SI). By extension they include units of
electromagnetism from the
CGS and SI units systems, and other units for which use of
SI prefix
The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...
es has become the norm. Other unit systems using metric units include:
*
International System of Electrical and Magnetic Units
*
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 (one, unit, unity) is a number representing a single or the only entity. 1 is also a numerical digit and represents a single unit of counting or measurement. For example, a line segment of ''unit length'' is a line segment of length 1. I ...
(1) is the unit of a
quantity of dimension one.
* The
second
The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...
(s) is the unit of
time.
* The
metre (m) is the unit of
length
Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In most systems of measurement a base unit for length is chosen, from which all other units are derived. In the Interna ...
.
* The
kilogram
The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...
(kg) is the unit of
mass.
* The
ampere
The ampere (, ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to elect ...
(A) is the unit of
electric current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
.
* The
kelvin (K) is the unit of
thermodynamic temperature.
* The
mole (mol) is the unit of
amount of substance
In chemistry, the amount of substance ''n'' in a given sample of matter is defined as the quantity or number of discrete atomic-scale particles in it divided by the Avogadro constant ''N''A. The particles or entities may be molecules, atoms, ions, ...
.
* The
candela (cd) is the unit of
luminous intensity.
* The
hertz (Hz) is equal to one
reciprocal second ().
* The
radian (rad) is equal to one ().
* The
steradian (sr) is equal to one ().
* The
newton
Newton most commonly refers to:
* Isaac Newton (1642–1726/1727), English scientist
* Newton (unit), SI unit of force named after Isaac Newton
Newton may also refer to:
Arts and entertainment
* ''Newton'' (film), a 2017 Indian film
* Newton ( ...
(N) is equal to one kilogram-metre per second squared ().
* The
pascal
Pascal, Pascal's or PASCAL may refer to:
People and fictional characters
* Pascal (given name), including a list of people with the name
* Pascal (surname), including a list of people and fictional characters with the name
** Blaise Pascal, Fren ...
(Pa) is equal to one newton per square metre ().
* The
joule (J) is equal to one newton-metre ().
* The
watt (W) is equal to one joule per second ().
* The
coulomb
The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI).
In the present version of the SI it is equal to the electric charge delivered by a 1 ampere constant current in 1 second and to elementary char ...
(C) is equal to one ampere second ().
* The
volt (V) is equal to one joule per coulomb ().
* The
weber
Weber (, or ; German: ) is a surname of German origin, derived from the noun meaning " weaver". In some cases, following migration to English-speaking countries, it has been anglicised to the English surname 'Webber' or even 'Weaver'.
Notable pe ...
(Wb) is equal to one volt-second ().
* The
tesla (T) is equal to one weber per square metre ().
* The
farad
The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base unit ...
(F) is equal to one coulomb per volt ().
* The
ohm (Ω) is equal to one volt per ampere ().
* The
siemens
Siemens AG ( ) is a German multinational conglomerate corporation and the largest industrial manufacturing company in Europe headquartered in Munich with branch offices abroad.
The principal divisions of the corporation are ''Industry'', '' ...
(S) is equal to one ampere per volt ().
* The
henry (H) is equal to one volt-second per ampere ().
* The
degree Celsius (°C) is equal to one kelvin ().
* The
lumen (lm) is equal to one candela-steradian ().
* The
lux
The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the ...
(lx) is equal to one lumen per square metre ().
* The
becquerel (Bq) is equal to one
reciprocal second ().
* The
gray (Gy) is equal to one joule per kilogram ().
* The
sievert (Sv) is equal to one joule per kilogram ().
* The
katal (kat) is equal to one mole per second ().
There are twenty-four
metric prefixes 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 (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 144t ...
, until which the
magnetic constant
The vacuum magnetic permeability (variously ''vacuum permeability'', ''permeability of free space'', ''permeability of vacuum''), also known as the magnetic constant, is the magnetic permeability in a classical vacuum. It is a physical 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 equal to .
* The
dyne (dyn) is a unit of
force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
equal to ().
* The
barye (Ba) is a unit of
pressure equal to ().
* The
erg (erg) is a unit of
energy equal to ().
* The
poise
Poise may mean:
* Poise (unit), a measure of viscosity
* A concept similar to gracefulness
* Ferdinand Poise
image:Ferdinand Poise 1892.jpg,
Jean Alexandre Ferdinand Poise (3 June 1828 – 13 May 1892) was a French composer, mainly of opéra ...
(P) is a unit of
dynamic 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 inter ...
equal to ().
* The
stokes (St) is a unit of
kinematic viscosity equal to ().
* The
stilb (sb) is a unit of
luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...
equal to ().
* The
phot (ph) is a unit of
illuminance equal to ().
* The
rayl
A Rayl, rayl or Rayleigh is one of two units of specific acoustic impedance or, equivalently, characteristic acoustic impedance; one an MKS unit, and the other a CGS unit. These have the same dimensions as momentum per volume.
The units are nam ...
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 equal to , which is equal to .
* The
statcoulomb (statC) or
franklin (Fr) is a unit of
electric charge equal to , corresponding to ~.
* The
statampere
The statampere (statA) is the derived electromagnetic unit of electric current in the CGS-ESU (electrostatic cgs) and Gaussian systems of units.
One statampere corresponds to / ampere ≈ in the SI system of units.
The name ''statampere'' is ...
(statA) is a unit of
electric current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
equal to , corresponding to ~.
* The
statvolt (statV) is a unit of
electric potential difference equal to , corresponding to .
* The
statohm The statohm is the unit of electrical resistance in the electrostatic system of units which was part of the CGS system of units based upon the centimetre, gram and second.
The static units in that system were related to the equivalent electromagn ...
is a unit of
electric resistance equal to , corresponding to ~.
* The
statsiemens or
statmho The statmho is the unit of electrical conductance in the electrostatic system of units (ESU), an extension of the centimeter-gram-second (CGS) system to cover electrical units. It is sometimes called the statsiemens, with symbol statS.
Conversio ...
is a unit of
electric conductance equal to , corresponding to ~.
* The
stathenry is a unit of
electric inductance
Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of th ...
equal to , corresponding to ~.
* The
statfarad
The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base units ...
(statF) is a unit of
electric capacitance
Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...
equal to , corresponding to ~.
* The statdaraf (statD) is a unit of
electric elastance
Electrical elastance is the multiplicative inverse, reciprocal of capacitance. The SI unit of elastance is the inverse farad (F−1). The concept is not widely used by electrical and electronic engineers. The value of capacitors is invariably ...
equal to 1/statF.
* The
statweber is a unit of
magnetic flux
In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the weber ( ...
, corresponding to .
* The
stattesla is a unit of
magnetic flux density equal to , corresponding to .
CGS-EMU electromagnetic units
* The
abwatt (abW) is a unit of
power equal to , which is equal to .
* The
abcoulomb (abC) is a unit of
electric charge equal to , corresponding to .
* The
abampere (abA) or
biot (Bi) is a unit of
electric current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
, corresponding to .
* The
abvolt (abV) is a unit of
electric potential difference, corresponding to .
* The
abohm (abΩ) is a unit of
electric resistance, corresponding to .
* The
abmho Abmho or absiemens is a unit of electrical conductance in the centimetre gram second (CGS-EMU) system of units. It corresponds to one gigasiemens (inverse nanoohm).
The CGS-EMU units are one of several systems of electromagnetic units that are su ...
is a unit of
electric conductance, corresponding to .
* The
abhenry is a unit of
electric inductance
Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of th ...
, corresponding to .
* The
abfarad (abF) is a unit of
electric capacitance
Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...
, corresponding to .
* The
gilbert (Gb) is a unit of
magnetomotive force equal to one biot-turn, corresponding to (10/4π) A = .
* The
oersted (Oe) is a unit of
magnetic field strength equal to , corresponding to (1000/4π) A/m = .
* The
maxwell
Maxwell may refer to:
People
* Maxwell (surname), including a list of people and fictional characters with the name
** James Clerk Maxwell, mathematician and physicist
* Justice Maxwell (disambiguation)
* Maxwell baronets, in the Baronetage o ...
(Mx) is a unit of
magnetic flux
In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the weber ( ...
, corresponding to .
* The
gauss (G) is a unit of
magnetic flux density, corresponding to .
CGS-Gaussian electromagnetic units
* The
franklin (Fr) is a unit of
electric charge equal to , corresponding to ~.
* The
oersted (Oe) is a unit of
magnetic field strength equal to , corresponding to ~.
* The
maxwell
Maxwell may refer to:
People
* Maxwell (surname), including a list of people and fictional characters with the name
** James Clerk Maxwell, mathematician and physicist
* Justice Maxwell (disambiguation)
* Maxwell baronets, in the Baronetage o ...
(Mx) is a unit of
magnetic flux
In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the weber ( ...
, corresponding to .
* The
gauss (G) is a unit of
magnetic flux density, corresponding to .
MTS
* The
tonne (t) is a unit of
mass equal to .
* The
sthène (sn) is a unit of
force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
equal to .
* The
pièze
The pièze () is the unit of pressure in the metre–tonne–second system of units (mts system), used, e.g., in the former Soviet Union 1933–1955. It is defined as one sthène
The sthène (; symbol sn), sometimes spelled (or misspelled) sthéne ...
(pz) is a unit of
pressure equal to .
MKSA
* The
cycle per second (cps or cyc/s) is a unit of
frequency equal to .
* The MKS
rayl
A Rayl, rayl or Rayleigh is one of two units of specific acoustic impedance or, equivalently, characteristic acoustic impedance; one an MKS unit, and the other a CGS unit. These have the same dimensions as momentum per volume.
The units are nam ...
is a unit of
acoustic impedance equal to .
* The
mho
The siemens (symbol: S) is the unit of electric conductance, electric susceptance, and electric admittance in the International System of Units (SI). Conductance, susceptance, and admittance are the reciprocals of resistance, reactance, and ...
(℧) is a unit of
electric conductance equal to .
MKpS units
* The
kilogram-force (kgf), also
kilopond (kp), is a unit of
force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
().
* The
hyl is a unit of
mass equal to ().
* The
poncelet (p) is a unit of
power equal to ().
* The
technical atmosphere (at) is a (non-coherent) unit of
pressure equal to ().
Other metric units
Length
* The
fermi is a unit of distance used in
nuclear physics equal to .
* The
angstrom (symbol Å) is a unit of distance used in
chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
and
atomic physics
Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. Atomic physics typically refers to the study of atomic structure and the interaction between atoms. It is primarily concerned wit ...
equal to .
* The
micron (μ) is a unit of distance equal to one
micrometre ().
* 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 ...
is a unit of distance equal to ten megametres ().
* The
spat (S) is a unit of distance equal to one
terametre
The following are examples of orders of magnitude for different lengths.
__TOC__
Overview
Detailed list
To help compare different orders of magnitude, the following list describes various lengths between 1.6 \times 10^ metres and 10 ...
().
Area
* The
shed
A shed is typically a simple, single-story roofed structure that is used for hobbies, or as a workshop in a back garden or on an allotment. Sheds vary considerably in their size and complexity of construction, from simple open-sided ones de ...
is a unit of area used in nuclear physics equal to 10
−24 barns (100 rm
2 = 10
−52 m
2).
* The
outhouse is a unit of area used in nuclear physics equal to 10
−6 barns (100 am
2 = 10
−34 m
2).
* The
barn (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
Are commonly refers to:
* Are (unit), a unit of area equal to 100 m2
Are, ARE or Åre may also refer to:
Places
* Åre, a locality in Sweden
* Åre Municipality, a municipality in Sweden
**Åre ski resort in Sweden
* Are Parish, a municipa ...
(a) is a unit of area equal to .
* The
decare (daa) is a unit of area equal to .
* The
hectare (ha) is a unit of area equal to .
Volume
* The
lambda (λ) is a unit of volume equal to one cubic
millimetre
330px, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is between 1 meter to 1 millimeter.
The millimetre (American and British English spelling differences#-re, -er, ...
(1 mm
3).
* The
litre (symbol l or L) is a unit of volume equal to one cubic
decimetre (1 dm
3).
* The
stere
The stere or stère (st) is a unit of volume in the original metric system equal to one cubic metre. The stere is typically used for measuring large quantities of firewood or other cut wood, while the cubic meter is used for uncut wood. The nam ...
(st) is a unit of volume equal to .
Reciprocal length
* The
dioptre
A dioptre (British spelling) or diopter (American spelling) is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dioptre = 1 m−1. It is normally used to express the optical power of a lens or curv ...
is a unit of
optical power equal to one
reciprocal metre ().
Time
* The
svedberg (S or Sv) is a unit of time used in chemistry equal to one hundred
femtosecond
A femtosecond is a unit of time in the International System of Units (SI) equal to 10 or of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. For context, a femtosecond is to a second as a second is to about 31. ...
s ().
* The
shake is a unit of time used in nuclear physics equal to ten
nanoseconds ().
* The
sigma
Sigma (; uppercase Σ, lowercase σ, lowercase in word-final position ς; grc-gre, σίγμα) is the eighteenth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 200. In general mathematics, uppercase Σ is used as ...
is a unit of time equal to one
microsecond ().
* The
jiffy is sometimes used to mean a unit of time of .
Reciprocal time
* The
fresnel is a unit of
frequency equal to .
Reciprocal time squared
* The
eotvos (E) is a unit of
gravitational gradient equal to ().
Speed
* The
benz
Benz, an old Germanic clan name dating to the fifth century (related to "bear", "war banner", "gau", or a "land by a waterway") also used in German () as an alternative for names such as Berthold, Bernhard, or Benedict, may refer to:
People Sur ...
is a unit of
speed equal to one metre per second (1 m/s).
Acceleration
* The leo is a unit of acceleration equal to .
Flow rate
* The
sverdrup (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 equal to ten picograms (10 pg).
* The gamma
Gamma (uppercase , lowercase ; ''gámma'') is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter re ...
(γ) is a unit of mass equal to one microgram (1 μg).
* The gravet is a unit of mass equal to one gram (1 g).
* The grave is a unit of mass equal to one kilogram (1 kg).
* The bar is a unit of mass equal to one megagram (1 Mg).
Linear mass density
* The tex (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 (msw) is a unit of pressure defined as 0.1 bar, which is equal to .
* The bar (bar) is a unit of pressure equal to .
Energy
* The foe
Friends of the Earth International (FoEI) is an international network of environmental organizations in 73 countries. The organization was founded in 1969 in San Francisco by David Brower, Donald Aitken and Gary Soucie after Brower's split w ...
is a unit of energy equal to ().
Viscosity
* The poiseuille is a unit of dynamic 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 inter ...
equal to one pascal-second ().
Electrical
* The Siemens mercury unit is a unit of electric resistance, corresponding to ~.
* The gamma (γ) a unit of magnetic flux density, corresponding to .
* The debye (D) is a unit of electric dipole moment
The electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. The SI unit for electric dipole moment is the coulomb-meter (C⋅m). The ...
equal to , corresponding to ~.
* The buckingham
Buckingham ( ) is a market town in north Buckinghamshire, England, close to the borders of Northamptonshire and Oxfordshire, which had a population of 12,890 at the 2011 Census. The town lies approximately west of Central Milton Keynes, sou ...
(B) is a unit of electric quadrupole moment equal to .
Electromagnetic radiation
* The jansky (Jy) is a unit of spectral irradiance equal to 10−26 W⋅m−2⋅Hz−1 ().
* The solar flux unit The solar flux unit (sfu) is a convenient measure of spectral flux density often used in solar radio observations, such as the F10.7 solar activity index:
:1 sfu = 104 Jy = 10−22 W⋅m−2⋅Hz−1 = 10−19 erg⋅s−1⋅cm−2⋅Hz� ...
is a unit of spectral irradiance equal to 10−22 W⋅m−2⋅Hz−1 ().
* The nox (nx) is a unit of illuminance equal to 1 millilux ().
* The nit (nt) is a unit of luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...
equal to one candela per metre squared ().
* The lambert
Lambert may refer to
People
*Lambert (name), a given name and surname
* Lambert, Bishop of Ostia (c. 1036–1130), became Pope Honorius II
*Lambert, Margrave of Tuscany ( fl. 929–931), also count and duke of Lucca
*Lambert (pianist), stage-name ...
(L) is a unit of luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...
equal to 104/π cd⋅m−2.
* The lumerg is a unit of luminous energy equal to lumen-seconds (100 nlm s).
* The talbot (T) is a unit of luminous energy equal to one lumen-second ().
* The 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 ...
(E) is a unit of amount of photons, equal to one mole (1 mol) of photons.
* The rayleigh Rayleigh may refer to:
Science
*Rayleigh scattering
*Rayleigh–Jeans law
*Rayleigh waves
*Rayleigh (unit), a unit of photon flux named after the 4th Baron Rayleigh
*Rayl, rayl or Rayleigh, two units of specific acoustic impedance and characte ...
(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) 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
The roentgen equivalent man (rem) is a CGS unit of equivalent dose, effective dose, and committed dose, which are dose measures used to estimate potential health effects of low levels of ionizing radiation on the human body.
Quantities measure ...
(rem) is a unit of equivalent dose 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 (W⋅h) is equal to .
* The watt hour per day
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 Watt ...
(W⋅h/d) is a unit of power equal to 3.6 kJ/(24 h) = 1/24 W.
* The enzyme unit (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 (SLPM) is approximately equal to (0.001/60) m3/s.
* The centimetre of water (cmH2O) is approximately .
* The millimetre of mercury (mmHg) is approximately .
* The torr (Torr) is approximately 133.3224 pascals.
* The centimetre of mercury (cmHg) is approximately .
* The electronvolt (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 (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
The neper (symbol: Np) is a logarithmic unit for ratios of measurements of physical field and power quantities, such as gain and loss of electronic signals. The unit's name is derived from the name of John Napier, the inventor of logarithms. As ...
(Np) is a unit of logarithmic ratio equal to 1.
* The percent
In mathematics, a percentage (from la, per centum, "by a hundred") is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign, "%", although the abbreviations "pct.", "pct" and sometimes "pc" are also use ...
(%) is equal to one part in a hundred (0.01).
* The permille (‰) is equal to one part in a thousand (0.001).
* The permyriad (‱) is equal to one part in ten thousand ().
* The part per million (ppm) is equal to one part in a million ().
* The part per billion (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 is equal to twenty five millimetre
330px, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is between 1 meter to 1 millimeter.
The millimetre (American and British English spelling differences#-re, -er, ...
s ().
* The cun is equal to one tenth of a chi (approximately 33.3333 mm).
* The metric foot 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 (''mil'') is equal to ten kilometres ().
* The metric dunam is equal to one thousand metres squared ().
* The stremma 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 u ...
is equal to .
* The metric carat
The carat (ct) is a unit of mass equal to or 0.00643 troy oz, and is used for measuring gemstones and pearls.
The current definition, sometimes known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Meas ...
(ct) is equal to .
* The li is equal to one ten-thousandth of a jin (50 mg).
* The fen 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
The pound or pound-mass is a Units of measurement, unit of mass used in imperial units, British imperial and United States customary units, United States customary systems of measurement. Various definitions have been used; the most common tod ...
is equal to .
* The jin (or catty) is equal to 500 g.
* The dan 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 (approximately 0.0303030 mm).
* The rin Rin may refer to:
*, yen, former Japanese currency
*Rin (given name)
*Rin (detergent), a brand of detergent sold by Unilever
*Rin, a Japanese standing bell
* ''Mnemosyne'' (anime) or ''RIN: Daughters of Mnemosyne'', an anime
*''Rin!'' (凛!), a Jap ...
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 is equal to one tenth of a shaku (approximately 30.3030 mm).
* The shaku is equal to 10/33 m (approximately 303.030 mm).
* The jo is equal to ten shaku (approximately 3030.30 mm).
* The metric mile
A metric mile is a colloquial term used in some countries for the 1500 meters, the premier middle distance running event in international track and field. The term 'metric mile' (0.93 statute miles) was applied to this distance because it appr ...
is equal to .
* The tsubo is equal to 400/121 metres squared (approximately 3.306 m2).
* The sho 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 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, electrica ...
* Gaussian units
* Gravitational metric system
* History of the metric system
* Metric system
* 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 French ...
* RKM code
* Unified Code for Units of Measure
Notes
References
{{Reflist
Metric system