# Units and Symbols Found in the UDUNITS2 Database

The UDUNITS2 package provides recognition and conversion of wide variety of measurement units. This page contains a full list of all of the units and prefixes, by name and by symbol, contained in the UDUNIT2 units database. Each entry shows the definition of the unit or symbol and lists the other units and symbols that share that same definition.

These tables are based on UDUNITS version 2.2.19

## Units by Name

Unit Plural Formula Definition Symbol(s) Other names
abampere abamperes 10 A basic unit of electricity in the electromagnetic CGS system of units
abhenry abhenries 1e-9 H unit of electricity/magnetism (exact)
abmho abmhos 1e9 S unit of electricity/magnetism (exact)
abohm abohms 1e-9 ohm unit of electricity/magnetism (exact)
abvolt abvolts 1e-8 V unit of electricity/magnetism (exact)
acre acres 160 rod ^2 unit of area in the US Customary System, used in land and sea floor measurement, equal to 43560 square feet (exact)
acre_foot acre_feet 1.233489e3 m ^3 unit of volume used to describe large-scale water resources in the United State; equal to the volume of one acre of surface area with one foot of depth depth (An “acre.foot”, however, is 1233.4867714897 m^3. Odd.)
amp amps A unit of electric current, synonym for ampere (Synonym for SI unit)
ampere amperes Base SI unit The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2e-7 newton per meter of length. A
amu 1.6605402e-27 kg standard unit for indicating mass on an atomic or molecular scale; is approximately the mass of one nucleon (either a single proton or neutron), and equivalent to 1 g/mol (Unit’s value is obtained experimentally) u atomic_mass_unit , atomicmassunit , unified_atomic_mass_unit
angstrom angstroms 1e-10 m unit of length equal to one hundred-millionth of a centimeter (1 meter/10**10) (Unit is temporarily accepted for use with the SI.) Å , ångström
angular_degree angular_degrees (pi /180) rad measurement of a plane angle representing 1/360 of a full rotation ° arc_degree , arcdeg , degree
angular_minute angular_minutes ° /60 measurement of a plane angle equal to 1/60 arc degree , arc_minute , arcmin , arcminute
angular_second angular_seconds /60 measurement of a plane angle equal to 1/60 arc minute , arc_second , arcsec , arcsecond
apdram apdrams 60 grain unit of mass in apothecaries’ weight system (is 1/8 apounce)
apostilb apostilbs cd /(pi m ^2) unit of illumination (exact) blondel
apothecary_ounce apothecary_ounces 3.110348e-2 kg unit of mass; based on historical US troy weight system (is 1/12 troy pound) troy_ounce
apothecary_pound apothecary_pounds 3.732417e-1 kg unit of mass; based on historical US troy weight system (is 5760 grain) troy_pound
apounce apounces 480 grain unit of mass in apothecaries’ weight system (is 1/16 appound)
appound appounds 5760 grain unit of mass in apothecaries’ weight system (is same as a troy pound)
arc_degree arc_degrees (pi /180) rad measurement of a plane angle representing 1/360 of a full rotation ° angular_degree , arcdeg , degree
arc_minute arc_minutes ° /60 measurement of a plane angle equal to 1/60 arc degree , angular_minute , arcmin , arcminute
arc_second arc_seconds /60 measurement of a plane angle equal to 1/60 arc minute , angular_second , arcsec , arcsecond
arcdeg arcdegs (pi /180) rad measurement of a plane angle representing 1/360 of a full rotation ° angular_degree , arc_degree , degree
arcmin arcmins ° /60 measurement of a plane angle equal to 1/60 arc degree , angular_minute , arc_minute , arcminute
arcminute arcminutes ° /60 measurement of a plane angle equal to 1/60 arc degree , angular_minute , arc_minute , arcmin
arcsec arcsecs /60 measurement of a plane angle equal to 1/60 arc minute , angular_second , arc_second , arcsecond
arcsecond arcseconds /60 measurement of a plane angle equal to 1/60 arc minute , angular_second , arc_second , arcsec
are ares dam ^2 unit of area equal to 100 square meters (Unit is temporarily accepted for use with the SI.) a
arpentlin arpentlins 191.835 foot unit of length in French regions; a linear arpent is of length 10 perch (10 rod)
assay_ton assay_tons 2.916667e-2 kg reference unit of mass for a body of ore; roughly equal to 29167 milligrams
astronomical_unit astronomical_units 1.495979e11 m unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun (Unit’s value is obtained experimentally) ua
atmosphere atmospheres 1.01325e5 Pa unit of pressure, an international reference pressure intended to represent the mean atmospheric pressure at mean sea level at the latitude of Paris, France (exact) atm standard_atmosphere
atomic_mass_unit atomic_mass_units 1.6605402e-27 kg standard unit for indicating mass on an atomic or molecular scale; is approximately the mass of one nucleon (either a single proton or neutron), and equivalent to 1 g/mol (Unit’s value is obtained experimentally) u amu , atomicmassunit , unified_atomic_mass_unit
atomicmassunit atomicmassunits 1.6605402e-27 kg standard unit for indicating mass on an atomic or molecular scale; is approximately the mass of one nucleon (either a single proton or neutron), and equivalent to 1 g/mol (Unit’s value is obtained experimentally) u amu , atomic_mass_unit , unified_atomic_mass_unit
avogadro_constant 6.02214179e23/mol number of constituent particles (usually atoms or molecules) per mole of a given substance (Constant; value is +-30e15)
avoirdupois_ounce avoirdupois_ounces 2.834952e-2 kg unit of mass equal to 1/16 avoirdupois pound, commonly used in the United States (16 oz = 1 pound = 7000 grains)
avoirdupois_pound avoirdupois_pounds 4.5359237e-1 kg unit of mass in avoirdupois system of weights (a system commonly used in United States) lb pound
bag bags 94 pound unit of mass, for a traditional bag of portland cement
bar bars 1000 hPa unit of pressure equal to 100000 Pascals, or about 0.987 atmospheres of pressure (Unit is temporarily accepted for use with the SI.)
barie baries 0.1 N /m ^2 unit of pressure equal to one dyne per square centimeter (exact) barye
barleycorn barleycorns inch /3 unit of length based in medieval laws of England and Wales, defining an inch as being 3 barleycorns long (length of a corn of barley); still the basis for current shoe sizes in Great Britain and Ireland
barn barns 100 fm ^2 unit of area, approximately the cross-sectional area of a uranium nucleus (10e-28 square meters) (Unit is temporarily accepted for use with the SI.) b
barrel barrels 42 US_liquid_gallon unit of volume used by US and Canadian petroleum organizations (The following is the definition of the petroleum industry) bbl
barye baryes 0.1 N /m ^2 unit of pressure equal to one dyne per square centimeter (exact) barie
baud bauds Hz unit of frequency, synonym for hertz (Synonym for SI unit) Bd , bps
becquerel (Is an alias because ‘1/s’ is already mapped to ‘hertz’ and ‘Hz’) becquerels 1/s unit of radioactivity; the activity of a quantity of material in which one nucleus decays per second (hence, equivalent to one unit per second) (SI derived unit with special names/symbols admitted for reasons of safeguarding human health) Bq
big_point big_points inch /72 unit of length equal to 1/72 inch, standardized unit in modern computer-based publishing for measuring font size and other small items on a printed page (contrast to printers_point)
biot biots 10 A basic unit of electricity in the electromagnetic CGS system of units (same as abampere), named after Jean-Baptiste Biot
bit bits 1 count
blondel blondels cd /(pi m ^2) unit of illumination (exact) apostilb
board_foot board_feet 2.359737e-3 m ^3 unit of volume equal to the cubic contents of a piece of lumber one foot square and one inch thick, used in measuring logs and lumber in the United States and Canada
boiler_horsepower boiler_horsepowers 9.80950e3 W unit of power equal to the power required to evaporate 34.5 lb of fresh water at 212 degrees F in one hour; describes a boiler’s capacity to deliver steam to a steam engine
Btu Btus 1.05505585262e3 J unit of energy, equal to the energy needed to cool or heat one pound of water by one degree F; this uses the International Steam Table (IT) calorie , defined by the Fifth International Conference on the properties of Steam (1956) (exact) IT_Btu
bushel bushels 3.523907e-2 m ^3 unit of volume defined as 2150.42 cubic inches or 4 pecks in the US Customary system (and formerly in England), where it is used as a dry measure bu
byte bytes 8 octet
calorie calories 4.1868 J unit of heat energy used in thermochemistry, the International Steam Table (IT) calorie defined by the Fifth International Conference on the properties of Steam (1956) (exact) cal IT_calorie
Canadian_liquid_gallon Canadian_liquid_gallons 4.546090e-3 m ^3 unit of volume for liquids in the Imperial system (exact)
candela candelas Base SI unit The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540e12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. cd
candle candles cd unit of luminous intensity, synonym for candela (Synonym for SI unit)
carat carats 2e-4 kg unit of mass equal to 0.2 gram (defined 1907)
celsius celsiuses degree_Celsius unit of temperature, synonym for ‘K @ 273.15’ (degree_Celsius) (Synonym for SI unit) degC , deg_C , degreeC , degree_C
chain chains 2.011684e1 m unit of length equal to 66 feet (4 poles), or 1/10 furlong, a typical (historical) scale of land surveying
circle circles 2 pi rad unit of angle in a plane signifying a full 360-degree circle cycle , revolution , rotation , turn
circular_mil circular_mils 5.067075e-10 m ^2 unit of area equal to the area of a one-mil diameter circle
clo clos 1.55e-1 K .m ^2/W unit of thermal resistance used in describing the insulating value of clothing; the amount of thermal resistance needed to maintain in comfort a resting subject in a normally ventilated room (air movement 10 cm/sec) at a temperature of 20 degrees C and a humidity less than 50%
common_year common_years 365 day unit of time corresponding to a ‘normal’ calendar year, that is, one without insertion of a leap day
conventional_mercury conventional_mercuries gravity 13595.10 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of mercury at 0 degrees C Hg mercury_0C , mercury_32F
conventional_water conventional_waters gravity 1000 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of water (exact) H2O , h2o water
coulomb coulombs s .A standard unit of electric charge, the quantity of electricity transported in one second by a current of one ampere (SI derived unit) C
count counts 1 bit
cup cups US_liquid_gallon /16 unit of volume for liquid measure in the US Customary system, equal to 1/16 liquid gallon (exact) US_liquid_cup , liquid_cup
curie curies 3.7e10 Bq unit of radioactivity corresponding to 3.7 * 10e10 disintegrations per second (Unit is temporarily accepted for use with the SI.) Ci
cycle cycles 2 pi rad unit of angle in a plane signifying a full 360-degree circle circle , revolution , rotation , turn
darcy darcies 9.869233e-13 m ^2 unit of area for measuring permeability to fluid, equal to 1 cubic centimeter of fluid with 1 centipoise viscosity in 1 second through a 1-square-centimeter cross section of porous medium 1 centimeter long at 1 atmosphere (porous solid permeability)
day days 24 h period of time equal to 24 hours d
deg_C degs_C degree_Celsius unit of temperature, synonym for ‘K @ 273.15’ (degree_Celsius) (Synonym for SI unit) celsius , degC , degreeC , degree_C
deg_F degs_F °R @ 459.67 unit of thermodynamic temperature °F , degF , degreeF , degree_F , degree_fahrenheit , fahrenheit
deg_K degs_K K unit of temperature, synonym for kelvin (Synonym for SI unit) °K degK , degreeK , degree_K , degree_kelvin
deg_R degs_R K /1.8 unit of thermodynamic temperature °R degR , degreeR , degree_R , degree_rankine
degC degsC degree_Celsius unit of temperature, synonym for ‘K @ 273.15’ (degree_Celsius) (Synonym for SI unit) celsius , deg_C , degreeC , degree_C
degF degsF °R @ 459.67 unit of thermodynamic temperature °F , deg_F , degreeF , degree_F , degree_fahrenheit , fahrenheit
degK degsK K unit of temperature, synonym for kelvin (Synonym for SI unit) °K deg_K , degreeK , degree_K , degree_kelvin
degR degsR K /1.8 unit of thermodynamic temperature °R deg_R , degreeR , degree_R , degree_rankine
degree degrees (pi /180) rad measurement of a plane angle representing 1/360 of a full rotation ° angular_degree , arc_degree , arcdeg
degree_C degrees_C degree_Celsius unit of temperature, synonym for ‘K @ 273.15’ (degree_Celsius) (Synonym for SI unit) celsius , degC , deg_C , degreeC
degree_Celsius degrees_Celsius K @ 273.15 unit (and scale) of temperature, with same magnitude as the kelvin and a zero-point offset of 273.15 (SI derived unit) °C
degree_E degrees_E arc_degree unit of angle on a sphere degreeE , degreeN , degreeT , degree_N , degree_T , degree_east , degree_north , degree_true
degree_east degrees_east arc_degree unit of angle on a sphere degreeE , degreeN , degreeT , degree_E , degree_N , degree_T , degree_north , degree_true
degree_F degrees_F °R @ 459.67 unit of thermodynamic temperature °F , degF , deg_F , degreeF , degree_fahrenheit , fahrenheit
degree_fahrenheit degrees_fahrenheit °R @ 459.67 unit of thermodynamic temperature °F , degF , deg_F , degreeF , degree_F , fahrenheit
degree_K degrees_K K unit of temperature, synonym for kelvin (Synonym for SI unit) °K degK , deg_K , degreeK , degree_kelvin
degree_kelvin degrees_kelvin K unit of temperature, synonym for kelvin (Synonym for SI unit) °K degK , deg_K , degreeK , degree_K
degree_N degrees_N arc_degree unit of angle on a sphere degreeE , degreeN , degreeT , degree_E , degree_T , degree_east , degree_north , degree_true
degree_north degrees_north arc_degree unit of angle on a sphere degreeE , degreeN , degreeT , degree_E , degree_N , degree_T , degree_east , degree_true
degree_R degrees_R K /1.8 unit of thermodynamic temperature °R degR , deg_R , degreeR , degree_rankine
degree_rankine degrees_rankine K /1.8 unit of thermodynamic temperature °R degR , deg_R , degreeR , degree_R
degree_T degrees_T arc_degree unit of angle on a sphere degreeE , degreeN , degreeT , degree_E , degree_N , degree_east , degree_north , degree_true
degree_true degrees_true arc_degree unit of angle on a sphere degreeE , degreeN , degreeT , degree_E , degree_N , degree_T , degree_east , degree_north
degree_W degrees_W -1 degree_east unit of angle on a sphere (units for negative direction) degreeW , degree_west
degree_west degrees_west -1 degree_east unit of angle on a sphere (units for negative direction) degreeW , degree_W
degreeC degreesC degree_Celsius unit of temperature, synonym for ‘K @ 273.15’ (degree_Celsius) (Synonym for SI unit) celsius , degC , deg_C , degree_C
degreeE degreesE arc_degree unit of angle on a sphere degreeN , degreeT , degree_E , degree_N , degree_T , degree_east , degree_north , degree_true
degreeF degreesF °R @ 459.67 unit of thermodynamic temperature °F , degF , deg_F , degree_F , degree_fahrenheit , fahrenheit
degreeK degreesK K unit of temperature, synonym for kelvin (Synonym for SI unit) °K degK , deg_K , degree_K , degree_kelvin
degreeN degreesN arc_degree unit of angle on a sphere degreeE , degreeT , degree_E , degree_N , degree_T , degree_east , degree_north , degree_true
degreeR degreesR K /1.8 unit of thermodynamic temperature °R degR , deg_R , degree_R , degree_rankine
degreeT degreesT arc_degree unit of angle on a sphere degreeE , degreeN , degree_E , degree_N , degree_T , degree_east , degree_north , degree_true
degreeW degreesW -1 degree_east unit of angle on a sphere (units for negative direction) degree_W , degree_west
denier deniers 1.111111e-7 kg /m unit of lineic mass density for fibers, equal to the mass in grams per 9000 meters (more common in United States and United Kingdom); a single strand of silk is approximately one denier
dobson dobsons 446.2 micromoles /meter ^2 DU
dram drams avoirdupois_ounce /16 unit of mass in the avoirdupois system (the system commonly used in the United States) (exact) dr
dry_pint dry_pints US_dry_gallon /8 unit of volume for dry measure in the US Customary system, equal to 1/2 US dry quart (exact) US_dry_pint
dry_quart dry_quarts US_dry_gallon /4 unit of volume for dry measure in the US Customary system, equal to 1/32 US bushel (exact) US_dry_quart
dynamic dynamics gravity (exact) gp geopotential
dyne dynes 1e-5 N unit of force, equal to the force that produces an acceleration of one centimeter per second per second on a mass of one gram (the standard centimeter-gram-second unit of force) (exact)
EC_therm EC_therms 1.05506e8 J unit of energy legally defined by the Council Directive of 20 December 1979, Council of the European Communities (now the European Union, EU);.roughly equal to 100,000 IT_Btu (exact (reference NIST Guide to SI Units))
einstein einsteins mole unit of chemical mass, synonym for mole (Synonym for SI unit)
electric_horsepower electric_horsepowers 7.460000e2 W unit of power defined in the International System of Units as exactly 746 W; generally used for power used by electrical machines (exact)
electron_volt electron_volts 1.60217733e-19 J unit of energy equal to the work accelerating an electron through a potential difference of one volt (Unit’s value is obtained experimentally) eV electronvolt
electronvolt electronvolts 1.60217733e-19 J unit of energy equal to the work accelerating an electron through a potential difference of one volt (Unit’s value is obtained experimentally) eV electron_volt
eon eons 1e9 year unit of time defined in astronomy as 1 billion years
erg ergs 1e-7 J unit of work, equal to the amount of work done by a force of one dyne exerted for a distance of one centimeter (in CGS base units, one gram centimeter-squared per second-squared) (exact)
fahrenheit fahrenheits °R @ 459.67 unit of thermodynamic temperature °F , degF , deg_F , degreeF , degree_F , degree_fahrenheit
farad farads C /V standard unit of capacitance; the amount which, when a capacitor is charged to a potential difference of one volt, carries a charge of one coulomb (SI derived unit) F
fathom fathoms 6 US_survey_feet unit of length equal to 6 feet in the imperial and US customary systems, typically used for measuring depth of water
fermi fermis 1e-15 m unit of length equal to 10e-15 meters, a typical length-scale of nuclear physics
firkin firkins barrel /4 unit of volume whose exact quantity depends on the type of barrel on which it is defined; in this table it is defined based on the oil barrel used by the petroleum industry (The following is exact regardless of the definition of “barrel”)
fluid_dram fluid_drams US_fluid_ounce /8 unit of volume for liquid measure in the apothecary system, equal to 1/8 liquid ounce (exact) fldr
fluid_ounce fluid_ounces US_liquid_gallon /128 unit of volume for liquid measure in the US Customary system, equal to 1/128 liquid gallon (exact) floz , oz US_fluid_ounce , US_liquid_ounce , liquid_ounce
foot feet 12 international_inches unit of length equal to 12 international inches, in the imperial and US customary systems; primarily used in the United States ft international_foot
foot_H2O feet_H2O foot water unit of pressure representing the pressure exerted by a column of water of 1 foot height at 4 degrees C ftH2O , fth2o footH2O , foot_water
foot_water feet_water foot water unit of pressure representing the pressure exerted by a column of water of 1 foot height at 4 degrees C ftH2O , fth2o footH2O , foot_H2O
footcandle footcandles 1.076391e-1 lx unit of illumination
footH2O feetH2O foot water unit of pressure representing the pressure exerted by a column of water of 1 foot height at 4 degrees C ftH2O , fth2o foot_H2O , foot_water
footlambert footlamberts 3.426259 cd /m ^2 unit of illumination (exact)
force forces standard_free_fall unit of force equivalent to the force generated by the effect of gravity
force_gram force_grams gram force unit of force, equal to the magnitude of the force exerted by one gram of mass in a 9.80665 m/s2 gravitational field (exact) gf gram_force
force_kilogram force_kilograms 9.806650 N unit of force, equal to the magnitude of the force exerted by one kilogram of mass in a 9.80665 m/s2 gravitational field (exact) kgf kilogram_force
force_ounce force_ounces 2.780139e-1 N unit of force, equal to the magnitude of the force exerted by one ounce of mass in a 9.80665 m/s2 gravitational field (exact) ozf ounce_force
force_pound force_pounds 4.4482216152605 N unit of force, equal to the magnitude of the force exerted by one pound of mass in a 9.80665 m/s2 gravitational field (exact) lbf pound_force
force_ton force_tons 2000 force_pound unit of force, equal to the magnitude of the force exerted by one ton of mass in a 9.80665 m/s2 gravitational field (specifically a short ton of mass) (exact) ton_force
fortnight fortnights 14 day unit of time commonly defined as 14 days
furlong furlongs 660 US_survey_feet unit of length equal to 1/8 mile or 10 chains
gal gals cm /s ^2 unit of acceleration equal to 1 cm per second squared (Unit is temporarily accepted for use with the SI.)
gallon gallons 3.785412e-3 m ^3 unit of volume for liquid measure in the US Customary system, defined as 3.785412 liters US_liquid_gallon , liquid_gallon
gamma gammas 1e-9 T unit of electricity/magnetism (exact)
gauss gausses 1e-4 T unit of electricity/magnetism (exact)
geopotential geopotentials gravity (exact) gp dynamic
gilbert gilberts 7.957747e-1 A unit of electricity/magnetism
gill gills US_liquid_gallon /32 unit of volume for liquid measure in the US Customary system, equal to 1/32 liquid gallon (exact) US_liquid_gill , liquid_gill
grain grains 6.479891e-5 kg unit of mass equal to 1/7000 pound gr
gram grams 1e-3 kg unit of mass equal to one thousandth of a kilogram (SI derived unit) g
gram_force grams_force gram force unit of force, equal to the magnitude of the force exerted by one gram of mass in a 9.80665 m/s2 gravitational field (exact) gf force_gram
gravity gravities standard_free_fall unit of acceleration synonymous with standard rate of free fall (in earth’s gravity) (should be local)
gray grays J /kg unit of ionizing radiation, a measure of the absorbed dose of radiation; absorption of one joule of radiation energy by one kilogram of matter (SI derived unit with special names/symbols admitted for reasons of safeguarding human health) Gy
Gregorian_year Gregorian_years 365.2425 day unit of time based on the Gregorian Calendar, the one commonly used today; approximates the tropical year as 365 + 97/400 days
hectare hectares 100 are unit of area equal to 100 are (‘hectoare’), or 10000 square meters (Unit is temporarily accepted for use with the SI.)
henry henries Wb /A unit of inductance; where a circuit’s current changes at a constant rate of 1 ampere per second, results in a generation of 1 V of potential difference (SI derived unit) H
hertz hertzs 1/s unit of frequency meaning one cycle per second (SI derived unit) Hz
horsepower horsepowers 7.456999e2 W unit of power originally corresponding to the estimated typical power of draft horses, calculated as lifting 33000 pounds one foot in one minute (550 foot-pounds/second) (shaft_horsepower is a unit of power as delivered by a drive shaft at its output (e.g., of a ship, aircraft engine, or helicopter rotor; typically not automobiles due to drive train losses)) hp shaft_horsepower
hour hours 60 min period of time equal to 60 minutes h , hr
inch inches 2.54 cm unit of length equal to 25.4 mm by definition, used in imperial and US customary systems in international_inch
inch_H2O_39F inches_H2O_39F inch water_39F unit of pressure representing the pressure exerted by a column of water of 1 inch height at 39 degrees F (exact)
inch_H2O_60F inches_H2O_60F inch water_60F unit of pressure representing the pressure exerted by a column of water of 1 inch height at 60 degrees F (exact)
inch_Hg inches_Hg inch Hg unit of pressure representing the pressure exerted by a column of mercury of 1 inch height at 0 degrees C inHg , in_Hg
inch_Hg_32F inches_Hg_32F inch mercury_32F unit of pressure representing the pressure exerted by a column of mercury of 1 inch height at 32 degrees F (exact)
inch_Hg_60F inches_Hg_60F inch mercury_60F unit of pressure representing the pressure exerted by a column of mercury of 1 inch height at 60 degrees F (exact)
international_foot international_feet 12 international_inches unit of length equal to 12 international inches, in the imperial and US customary systems; primarily used in the United States ft foot
international_inch international_inches 2.54 cm unit of length equal to 25.4 mm by definition, used in imperial and US customary systems in inch
international_knot international_knots nautical_mile /hour derived unit of speed at sea (Unit is temporarily accepted for use with the SI.) knot , knot_international
international_mile international_miles 5280 international_feet unit of length equal to 5280 feet, equal to 12 international inches, in the imperial and US customary systems; primarily used in the United States and other smaller countries with ties to the US or United Kingdom mi mile
international_yard international_yards 3 international_feet unit of length equal to 3 international feet, in the imperial and US customary systems; primarily used in the United States yd yard
IT_Btu IT_Btus 1.05505585262e3 J unit of energy, equal to the energy needed to cool or heat one pound of water by one degree F; this uses the International Steam Table (IT) calorie , defined by the Fifth International Conference on the properties of Steam (1956) (exact) Btu
IT_calorie IT_calories 4.1868 J unit of heat energy used in thermochemistry, the International Steam Table (IT) calorie defined by the Fifth International Conference on the properties of Steam (1956) (exact) cal calorie
jiffy jiffies 0.01 s unit of time used in computer animation as a method of defining playback rate (multiple values have been proposed for the amount of time represented by a ‘jiffy’)
joule joules N .m standard unit of work or energy, equal to the work done by a force of one newton acting along a distance of one meter (SI derived unit) J
Julian_year Julian_years 365.25 day unit of time recognized by the International Astronomical Union for use in astronomy, defined as 365.25 days of 86400 seconds
katal katals mol /s unit of catalytic activity (property of a catalyst, such as an enzyme); expresses the ability to break 1 mole of bonds per second under specified conditions (SI derived unit) kat
kayser kaysers 100/m (exact)
kelvin kelvins Base SI unit The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. K
kilogram kilograms Base SI unit The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram. kg
kilogram_force kilograms_force 9.806650 N unit of force, equal to the magnitude of the force exerted by one kilogram of mass in a 9.80665 m/s2 gravitational field (exact) kgf force_kilogram
kip kips 1000 lbf unit of force, equal to the magnitude of the force exerted by one thousand pounds of mass in a 9.80665 m/s2 gravitational field (exact)
knot knots nautical_mile /hour derived unit of speed at sea (Unit is temporarily accepted for use with the SI.) international_knot , knot_international
knot_international knot_internationals nautical_mile /hour derived unit of speed at sea (Unit is temporarily accepted for use with the SI.) international_knot , knot
lambert lamberts (1e4/pi ) cd /m ^2 unit of illumination (exact)
langley langleys 4.184000e4 J /m ^2 unit of illumination (exact)
leap_year leap_years 366 day unit of time corresponding to a calendar year with a leap day inserted
light_year light_years 9.46073e15 m unit of length equal to the distance traversed by light in one mean solar year (365.2422 days), a typical length-scale of astronomy
liquid_cup liquid_cups US_liquid_gallon /16 unit of volume for liquid measure in the US Customary system, equal to 1/16 liquid gallon (exact) US_liquid_cup , cup
liquid_gallon liquid_gallons 3.785412e-3 m ^3 unit of volume for liquid measure in the US Customary system, defined as 3.785412 liters US_liquid_gallon , gallon
liquid_gill liquid_gills US_liquid_gallon /32 unit of volume for liquid measure in the US Customary system, equal to 1/32 liquid gallon (exact) US_liquid_gill , gill
liquid_ounce liquid_ounces US_liquid_gallon /128 unit of volume for liquid measure in the US Customary system, equal to 1/128 liquid gallon (exact) floz , oz US_fluid_ounce , US_liquid_ounce , fluid_ounce
liquid_pint liquid_pints US_liquid_gallon /8 unit of volume for liquid measure in the US Customary system, equal to 1/8 liquid gallon (exact) pt US_liquid_pint , pint
liquid_quart liquid_quarts US_liquid_gallon /4 unit of volume for liquid measure in the US Customary system, equal to 1/4 liquid gallon (exact) US_liquid_quart , quart
liter liters dm ^3 unit of capacity equal to 1000 cubic centimeters (The definition is exact. From 1901 to 1964, however, 1 liter was 1.000028 dm^3 (volume of 1 kg of water under standard conditions).) L , l litre
litre litres dm ^3 unit of capacity equal to 1000 cubic centimeters (The definition is exact. From 1901 to 1964, however, 1 liter was 1.000028 dm^3 (volume of 1 kg of water under standard conditions).) L , l liter
long_hundredweight long_hundredweights 5.080235e1 kg unit of mass; a British hundredweight, which is 8 stone * 14 pounds/stone
long_ton long_tons 2240 pound unit of mass based on British imperial weight system
lumen lumens cd .sr unit of luminous flux, a measure of the total “amount” of visible light emitted by a source; one candela-steradian (SI derived unit) lm
lunar_month lunar_months 29.530589 day unit of time equal to the average time between successive new or full moons; equal to approximately 29 days, 12 hours, 44 minutes
lux luxes lm /m ^2 unit of illuminance and luminous emittance, measuring luminous flux per unit area, and used as a measure of intensity of light; equal to one lumen per square meter (SI derived unit) lx
maxwell maxwells 1e-8 Wb unit of electricity/magnetism (exact)
mercury_0C mercuries_0C gravity 13595.10 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of mercury at 0 degrees C Hg conventional_mercury , mercury_32F
mercury_32F mercuries_32F gravity 13595.10 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of mercury at 0 degrees C Hg conventional_mercury , mercury_0C
mercury_60F mercuries_60F gravity 13556.8 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of mercury at 60 degrees F
meter meters Base SI unit The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. m metre
metre metres Base SI unit The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. m meter
metric_horsepower metric_horsepowers 7.35499e2 W unit of power corresponding to a calculation of 75 kilogram-meters/second
metric_ton metric_tons 1000 kg unit of weight equal to 1000 kilograms t tonne
micron microns 1e-6 m unit of length, a typical length-scale of technology and science fields
mil mils 2.54e-5 m unit of length equal to 0.001 inch, a typical length-scale for measuring wire diameters
mile miles 5280 international_feet unit of length equal to 5280 feet, equal to 12 international inches, in the imperial and US customary systems; primarily used in the United States and other smaller countries with ties to the US or United Kingdom mi international_mile
millimeter_Hg millimeters_Hg mm Hg unit of pressure representing the pressure exerted by a column of mercury of 1 mm height at 0 degrees C; approximately (within 0.000015%, generally below measurement error) 1 Torr, which is 1/760 standard atmospheric pressure mmHg , mm_Hg , mm_hg , mmhg torr
millimeter_Hg_0C millimeters_Hg_0C mm mercury_0C unit of pressure representing the pressure exerted by a column of mercury of 1 mm height at 0 degrees C (exact)
minute minutes 60 s period of time equal to 60 seconds min
mole moles Base SI unit The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles. mol
molec molecs 1/avogadro_constant molecule , nuc , nucleon
molecule molecules 1/avogadro_constant molec , nuc , nucleon
month months year /12 unit of time defined as the average length of time for a calendar month
nautical_mile nautical_miles 1852 m unit of distance at sea, set at 1852 meters (approximately one minute of arc measured along any meridian) (Unit is temporarily accepted for use with the SI.)
newton newtons m .kg /s ^2 unit of force; the amount needed to accelerate 1 kilogram of mass at the rate of 1 metre per second squared (SI derived unit) N
nit nits 1 cd /m ^2 unit of illumination (exact) nt
nmile nmiles nautical_mile unit of length in the US Customary System, equal to 6,076 feet; typically used for air and sea navigation
nuc nucs 1/avogadro_constant molec , molecule , nucleon
nucleon nucleons 1/avogadro_constant molec , molecule , nuc
octet octets 8 byte
oersted oersteds 7.957747e1 A /m unit of electricity/magnetism Oe
ohm ohms V /A standard unit of electrical resistance; the resistance between two points of a conductor when a constant potential difference of 1.0 volt, applied to these points, produces in the conductor a current of 1.0 ampere (SI derived unit) , Ω
ounce_force ounces_force 2.780139e-1 N unit of force, equal to the magnitude of the force exerted by one ounce of mass in a 9.80665 m/s2 gravitational field (exact) ozf force_ounce
parsec parsecs 3.085678e16 m unit of length corresponding to the distance at which the mean radius of the earth’s orbit subtends an angle of one second of arc, a typical length-scale of astronomy
pascal pascals N /m ^2 unit of pressure (force per unit area) equal to one newton per square meter (SI derived unit) Pa
peck pecks bushel /4 unit of volume defined as 537.6 cubic inches in the US Customary system (and formerly in England), where it is used as a dry measure (exact) pk
pennyweight pennyweights 1.555174e-3 kg unit of mass; based on historical US troy weight system (is 1/20 troy ounce)
percent 0.01 number of parts per hundred (Constant) %
perch perches 16.5 US_survey_feet unit of length equal to one-fourth of a surveyor’s chain pole , rod
perm_0C perms_0C 5.72135e-11 kg /(Pa .s .m ^2) unit of mass per unit time (includes flow) for how fast water vapor flows through substance, or permeance; equals 1 gram of water vapor per hour, per square meter, per millimeter of mercury at 0 degrees C
perm_23C perms_23C 5.74525e-11 kg /(Pa .s .m ^2) unit of mass per unit time for how fast water vapor flows through substance, or permeance; equals 1 gram of water vapor per hour, per square meter, per millimeter of mercury at 23 degrees C
phot phots 1e4 lm /m ^2 unit of illumination (exact) ph
pi 3.141592653589793238462643383279 mathematical constant equal to the ratio of a circle’s circumference to its diameter (This “unit” is useful in the definition of subsequent units.) π
pica picas 12 printers_point unit of length equal to 1/6 inch (12 printers points) printers_pica
pint pints US_liquid_gallon /8 unit of volume for liquid measure in the US Customary system, equal to 1/8 liquid gallon (exact) pt US_liquid_pint , liquid_pint
poise poises 1e-1 Pa .s unit of dynamic viscosity, corresponding to 0.1 pascal-second (pascal-second: a fluid placed between two plates, when one plate is pushed sideways with a shear stress of one pascal, moves a distance equal to the thickness of the layer between the plates in one second) (exact)
pole poles 16.5 US_survey_feet unit of length equal to one-fourth of a surveyor’s chain perch , rod
pond ponds 9.806650e-3 N unit of force, equal to the magnitude of the force exerted by one gram of mass in a 9.80665 m/s2 gravitational field (exact)
potential_vorticity_unit potential_vorticity_units 1e-6 m ^2 s ^-1 K kg ^-1 (exact) PVU
pound pounds 4.5359237e-1 kg unit of mass in avoirdupois system of weights (a system commonly used in United States) lb avoirdupois_pound
pound_force pounds_force 4.4482216152605 N unit of force, equal to the magnitude of the force exerted by one pound of mass in a 9.80665 m/s2 gravitational field (exact) lbf force_pound
poundal poundals 1.382550e-1 N unit of force, that which is necessary to accelerate 1 pound-mass to 1 foot per second per second (exact)
printers_pica printers_picas 12 printers_point unit of length equal to 1/6 inch (12 printers points) pica
printers_point printers_points 3.514598e-4 m unit of length equal to 1/72.27 inch, the original (standardized 1886) unit for measuring font size and other small items on a printed page (see also big_point)
quart quarts US_liquid_gallon /4 unit of volume for liquid measure in the US Customary system, equal to 1/4 liquid gallon (exact) US_liquid_quart , liquid_quart
radian radians Dimensionless quantity standard unit of angular measure, an angle that creates an arc in a circle equal in length to that circle’s radius (roughly 57.3 degrees); as a ratio of two lengths, it has no dimension (SI derived unit) rad
refrigeration_ton refrigeration_tons 12000 Btu /hr unit of power describing the heat-extraction capacity of cooling equipment; defined as the heat absorbed by melting 1 short ton of pure ice at 0 degrees C in 24 hours ton_of_refrigeration
register_ton register_tons 2.831685 m ^3 unit of volume used for internal capacity of ships, equal to 100 cubic feet
rem rems cSv unit of radiation dosage applied to humans; equal to one hundredth of a sievert (Unit is temporarily accepted for use with the SI.)
revolution revolutions 2 pi rad unit of angle in a plane signifying a full 360-degree circle circle , cycle , rotation , turn
rhe rhes 10/(Pa .s ) unit of fluidity (reciprocal of velocity), measured in reciprocal poise (exact)
rod rods 16.5 US_survey_feet unit of length equal to one-fourth of a surveyor’s chain perch , pole
roentgen roentgens 2.58e-4 C /kg unit of ionizing radiation, the amount producing one electrostatic unit of positive or negative ionic charge in one cubic centimeter of air under standard conditions; rarely used (Unit is temporarily accepted for use with the SI.) R
rotation rotations 2 pi rad unit of angle in a plane signifying a full 360-degree circle circle , cycle , revolution , turn
rotation_per_second rotations_per_second rotation /second unit of angular velocity (exact) cps , rps
scruple scruples 20 grain unit of mass in apothecaries’ weight system (is 1/3 apdram)
sec secs s unit of time, synonym for second (Synonym for SI unit)
second seconds Base SI unit The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. s
shaft_horsepower shaft_horsepowers 7.456999e2 W unit of power originally corresponding to the estimated typical power of draft horses, calculated as lifting 33000 pounds one foot in one minute (550 foot-pounds/second) (shaft_horsepower is a unit of power as delivered by a drive shaft at its output (e.g., of a ship, aircraft engine, or helicopter rotor; typically not automobiles due to drive train losses)) hp horsepower
shake shakes 1e-8 s unit of time approximating the lifetime of an individual neutron, useful for describing very brief durations, e.g., in nuclear physics
short_hundredweight short_hundredweights 4.535924e1 kg unit of mass, a US hundredweight, which is 100 pounds
short_ton short_tons 2000 pound unit of mass based on US weight system ton
sidereal_day sidereal_days 8.616409e4 s unit of time that it takes the earth to complete one revolution with respect to a star, roughly 23 hours, 56 minutes, 4 seconds
sidereal_hour sidereal_hours 3.590170e3 s unit of time equal to 1/24 sidereal day
sidereal_minute sidereal_minutes 5.983617e1 s unit of time equal to 1/60 sidereal hour
sidereal_month sidereal_months 27.321661 day unit of time based on 1/12 of the sidereal year
sidereal_second sidereal_seconds 0.9972696 s unit of time equal to 1/60 sidereal second
sidereal_year sidereal_years 3.155815e7 s unit of time for the earth to make one complete revolution around the sun, relative to the fixed stars
siemens siemenses A /V unit of electric conductance; the reciprocal of one ohm (SI derived unit) S
sievert sieverts J /kg unit of ionizing radiation dose, measuring the health effect of low levels of ionizing radiation on the human body (SI derived unit with special names/symbols admitted for reasons of safeguarding human health) Sv
slug slugs 14.59390 kg unit of mass associated with Imperial units; a mass that accelerates by 1 ft/s2 when a force of one pound-force (lbF) is exerted on it
standard_atmosphere standard_atmospheres 1.01325e5 Pa unit of pressure, an international reference pressure intended to represent the mean atmospheric pressure at mean sea level at the latitude of Paris, France (exact) atm atmosphere
standard_free_fall standard_free_falls 9.806650 m /s ^2 unit of acceleration corresponding to the nominal gravitational acceleration of an object in a vacuum near the surface of earth (exact)
statampere statamperes 3.335640e-10 A unit of electricity/magnetism
statcoulomb statcoulombs 3.335640e-10 C unit of electricity/magnetism
stathenry stathenries 8.987554e11 H unit of electricity/magnetism
statmho statmhos 1.112650e-12 S unit of electricity/magnetism
statohm statohms 8.987554e11 ohm unit of electricity/magnetism
statvolt statvolts 2.997925e2 V unit of electricity/magnetism
steradian steradians rad ^2 standard unit of solid angle measure, it is the solid angle which cuts out an area on a sphere that is the square of the sphere’s radius; as a ratio of two areas, it has no dimension (SI derived unit) sr
stere steres 1 m ^3 unit of volume equal to a cubic meter, originally defined primarily as a measure for firewood (exact)
stilb stilbs 1e4 cd /m ^2 unit of illumination (exact) sb
stokes stokeses 1e-4 m ^2/s unit of kinematic viscosity, measuring the ratio of the dynamic viscosity to the density of the fluid; water at 20 degrees C has a kinematic viscosity about 100 stokes, or more cmomonly, 1 cSt (exact) St
sverdrup sverdrups 1e6 m ^3/s unit of volume transport, used almost exclusively to measure the volumetric rate of ocean currents (exact)
tablespoon tablespoons US_fluid_ounce /2 unit of volume for liquid measure in the US Customary system, equal to 1/2 liquid ounce (exact) Tbl , Tblsp , Tbsp , tblsp , tbsp
teaspoon teaspoons tablespoon /3 unit of volume defined as 1/3 tablespoon, the actual volume of which can vary depending on the measurement system (but is based on the US Customary system in this database) (exact) tsp
technical_atmosphere technical_atmospheres 1 kg gravity /cm 2 unit of pressure equal to one kilogram force per square centimeter (exact; note that the symbol ‘at’ clashes with that of the katal (‘kat’), the SI unit of catalytic activity) at
tesla teslas Wb /m ^2 unit of flux density, equal to one weber per square meter (SI derived unit) T
tex texes 1e-6 kg /m unit of lineic mass density for fibers, defined as mass in grams per 1000 meters (more common in Canada and Continental Europe) (exact)
therm therms 1.054804e8 J unit of energy legally defined in the U.S. Federal Register of July 27, 1968, and the legal unit used by the U.S. natural gas industry (exact) thm US_therm
thermochemical_calorie thermochemical_calories 4.184000 J unit of heat energy defined as 4.184 Joules exactly (International Standard ISO 31-4: Quantities and units, Part 4: Heat); approximately the energy needed to increase the temperature of 1 gram of water by 1 C (exact)
TNT 4.184 MJ /kg unit of energy; approximately the energy released by the detonation of a given amount of mass of TNT (by definition)
ton tons 2000 pound unit of mass based on US weight system short_ton
ton_force tons_force 2000 force_pound unit of force, equal to the magnitude of the force exerted by one ton of mass in a 9.80665 m/s2 gravitational field (specifically a short ton of mass) (exact) force_ton
ton_of_refrigeration tons_of_refrigeration 12000 Btu /hr unit of power describing the heat-extraction capacity of cooling equipment; defined as the heat absorbed by melting 1 short ton of pure ice at 0 degrees C in 24 hours refrigeration_ton
ton_TNT tons_TNT 4.184e9 J unit of energy; approximately the energy released by the detonation of a 1000 kilograms of TNT (by definition)
tonne tonnes 1000 kg unit of weight equal to 1000 kilograms t metric_ton
torr torrs mm Hg unit of pressure representing the pressure exerted by a column of mercury of 1 mm height at 0 degrees C; approximately (within 0.000015%, generally below measurement error) 1 Torr, which is 1/760 standard atmospheric pressure mmHg , mm_Hg , mm_hg , mmhg millimeter_Hg
tropical_month tropical_months 27.321582 day unit of time based on 1/12 of the tropical year
tropical_year tropical_years 3.15569259747e7 s unit of time; Interval between 2 successive passages of sun through vernal equinox (365.242198781 days). See http://www.ast.cam.ac.uk/pubinfo/leaflets/, http://aa.usno.navy.mil/AA/, and http://adswww.colorado.edu/adswww/astro_coord.html yr year
troy_ounce troy_ounces 3.110348e-2 kg unit of mass; based on historical US troy weight system (is 1/12 troy pound) apothecary_ounce
troy_pound troy_pounds 3.732417e-1 kg unit of mass; based on historical US troy weight system (is 5760 grain) apothecary_pound
turn turns 2 pi rad unit of angle in a plane signifying a full 360-degree circle circle , cycle , revolution , rotation
UK_fluid_ounce UK_fluid_ounces UK_liquid_gallon /160 unit of volume for liquid measure in the Imperial system, equal to 1/160 liquid gallon (exact) UK_liquid_ounce
UK_horsepower UK_horsepowers 7.4570e2 W unit of power originally corresponding to the estimated typical power of draft horses, calculated as lifting 33000 pounds one foot in one minute (550 foot-pounds/second), as calculated/specified in the United Kingdom
UK_liquid_cup UK_liquid_cups UK_liquid_gallon /16 unit of volume for liquid measure in the Imperial system, equal to 1/16 liquid gallon (exact)
UK_liquid_gallon UK_liquid_gallons 4.546090e-3 m ^3 unit of volume for liquid measure in the Imperial system (exact)
UK_liquid_gill UK_liquid_gills UK_liquid_gallon /32 unit of volume for liquid measure in the Imperial system, equal to 1/32 liquid gallon (exact)
UK_liquid_ounce UK_liquid_ounces UK_liquid_gallon /160 unit of volume for liquid measure in the Imperial system, equal to 1/160 liquid gallon (exact) UK_fluid_ounce
UK_liquid_pint UK_liquid_pints UK_liquid_gallon /8 unit of volume for liquid measure in the Imperial system, equal to 1/8 liquid gallon (exact)
UK_liquid_quart UK_liquid_quarts UK_liquid_gallon /4 unit of volume for liquid measure in the Imperial system, equal to 1/4 liquid gallon (exact)
unified_atomic_mass_unit unified_atomic_mass_units 1.6605402e-27 kg standard unit for indicating mass on an atomic or molecular scale; is approximately the mass of one nucleon (either a single proton or neutron), and equivalent to 1 g/mol (Unit’s value is obtained experimentally) u amu , atomic_mass_unit , atomicmassunit
unit_pole unit_poles 1.256637e-7 Wb unit of electricity/magnetism
US_dry_gallon US_dry_gallons 4.404884e-3 m ^3 unit of volume for dry measure in the US Customary system, defined as 1/2 peck or 1/8 bushel
US_dry_pint US_dry_pints US_dry_gallon /8 unit of volume for dry measure in the US Customary system, equal to 1/2 US dry quart (exact) dry_pint
US_dry_quart US_dry_quarts US_dry_gallon /4 unit of volume for dry measure in the US Customary system, equal to 1/32 US bushel (exact) dry_quart
US_fluid_ounce US_fluid_ounces US_liquid_gallon /128 unit of volume for liquid measure in the US Customary system, equal to 1/128 liquid gallon (exact) floz , oz US_liquid_ounce , fluid_ounce , liquid_ounce
US_liquid_cup US_liquid_cups US_liquid_gallon /16 unit of volume for liquid measure in the US Customary system, equal to 1/16 liquid gallon (exact) cup , liquid_cup
US_liquid_gallon US_liquid_gallons 3.785412e-3 m ^3 unit of volume for liquid measure in the US Customary system, defined as 3.785412 liters gallon , liquid_gallon
US_liquid_gill US_liquid_gills US_liquid_gallon /32 unit of volume for liquid measure in the US Customary system, equal to 1/32 liquid gallon (exact) gill , liquid_gill
US_liquid_ounce US_liquid_ounces US_liquid_gallon /128 unit of volume for liquid measure in the US Customary system, equal to 1/128 liquid gallon (exact) floz , oz US_fluid_ounce , fluid_ounce , liquid_ounce
US_liquid_pint US_liquid_pints US_liquid_gallon /8 unit of volume for liquid measure in the US Customary system, equal to 1/8 liquid gallon (exact) pt liquid_pint , pint
US_liquid_quart US_liquid_quarts US_liquid_gallon /4 unit of volume for liquid measure in the US Customary system, equal to 1/4 liquid gallon (exact) liquid_quart , quart
US_statute_mile US_statute_miles 5280 US_survey_feet unit of length used for earlier survey data in some countries, slightly slightly different than the current international mile US_survey_mile
US_survey_foot US_survey_feet (1200/3937) m unit of length used for earlier survey data in some countries, slightly different than the current international foot
US_survey_mile US_survey_miles 5280 US_survey_feet unit of length used for earlier survey data in some countries, slightly slightly different than the current international mile US_statute_mile
US_survey_yard US_survey_yards 3 US_survey_feet unit of length used in earlier survey data in some countries, slightly different than the current international yard
US_therm US_therms 1.054804e8 J unit of energy legally defined in the U.S. Federal Register of July 27, 1968, and the legal unit used by the U.S. natural gas industry (exact) thm therm
volt volts W /A standard unit of electric potential difference (and electromotive force); the difference of potential between two points of a conductor carrying a constant current of one ampere and dissipating one watt of power (SI derived unit) V
voltampere voltamperes V .A unit of electric power equal to the product of one volt and one ampere, equivalent to one watt for direct current systems and a unit of apparent power for alternating current systems (exact) VA
water waters gravity 1000 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of water (exact) H2O , h2o conventional_water
water_39F (actually 39.2 F) waters_39F gravity 999.972 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of water at 4 degrees C water_4C
water_4C waters_4C gravity 999.972 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of water at 4 degrees C water_39F
water_60F waters_60F gravity 999.001 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of water at 60 degrees F
water_horsepower water_horsepowers 7.46043e2 W unit of power used in the U.S. primarily in rating pumps; calculated as pump capacity Q (gallons per minute) times pump pressure (“head”) of P (feet of head), divided by 3956 water horsepower; the calculation assumes water density is 8 1/3 pounds per U.S. gallon, which is not exact.
watt watts J /s standard unit of power, equivalent to one joule per second, and equal to one ampere flowing across a potential difference of one volt (SI derived unit) W
watthour watthours watt .hour unit of energy equal to the product of the power in watts and the time in hours (if the energy is being transmitted or used at a constant rate (power) over a period of time); one watt is equal to 1 Joule/second (exact)
weber webers V .s unit of magnetic flux (product of the average magnetic field times the perpendicular area that it penetrates), expressed as volt-seconds (SI derived unit) Wb
week weeks 7 day unit of time commonly defined as 7 days
work_month work_months work_year /12 (exact)
work_year work_years 2056 hours (exact)
yard yards 3 international_feet unit of length equal to 3 international feet, in the imperial and US customary systems; primarily used in the United States yd international_yard
year years 3.15569259747e7 s unit of time; Interval between 2 successive passages of sun through vernal equinox (365.242198781 days). See http://www.ast.cam.ac.uk/pubinfo/leaflets/, http://aa.usno.navy.mil/AA/, and http://adswww.colorado.edu/adswww/astro_coord.html yr tropical_year
ångström ångströms 1e-10 m unit of length equal to one hundred-millionth of a centimeter (1 meter/10**10) (Unit is temporarily accepted for use with the SI.) Å , angstrom

## Units by Symbol

Symbol Formula Definition Name(s) Other Symbols
/60 measurement of a plane angle equal to 1/60 arc minute angular_second , arc_second , arcsec , arcsecond
% 0.01 number of parts per hundred (Constant) percent
° /60 measurement of a plane angle equal to 1/60 arc degree angular_minute , arc_minute , arcmin , arcminute
a dam ^2 unit of area equal to 100 square meters (Unit is temporarily accepted for use with the SI.) are
A Base SI unit The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2e-7 newton per meter of length. ampere
at 1 kg gravity /cm 2 unit of pressure equal to one kilogram force per square centimeter (exact; note that the symbol ‘at’ clashes with that of the katal (‘kat’), the SI unit of catalytic activity) technical_atmosphere
atm 1.01325e5 Pa unit of pressure, an international reference pressure intended to represent the mean atmospheric pressure at mean sea level at the latitude of Paris, France (exact) atmosphere , standard_atmosphere
b 100 fm ^2 unit of area, approximately the cross-sectional area of a uranium nucleus (10e-28 square meters) (Unit is temporarily accepted for use with the SI.) barn
B_SPL lg(re 20e-6 Pa ) logarithmic unit used to compare the sound pressure of an unknown sound to a standard reference sound pressure; is the base unit for “dB_SPL”, a more typical logarithmic unit for measuring sound pressure (the SI unit for sound pressure is pascal); the standard reference sound pressure in air or other gases is 20 microPascal, which is usually considered the threshold of human hearing (at 1 kHz) (sound pressure level)
bbl 42 US_liquid_gallon unit of volume used by US and Canadian petroleum organizations (The following is the definition of the petroleum industry) barrel
Bd Hz unit of frequency, synonym for hertz (Synonym for SI unit) baud bps
bev 1e9 eV unit of energy corresponding to 1 billion electron volts (eV) (exact)
Bm lg(re 1 mW ) unit of power in decibel scale, referenced to 1 milliwatt; the power in bel-milliwatts is equal to 100 times the base 10 logarithm of the power in milliwatts (making decibel-milliwatt, the more common term, 10 times the base 10 log of the power in watts)
bps Hz unit of frequency, synonym for hertz (Synonym for SI unit) baud Bd
Bq (Is an alias because ‘1/s’ is already mapped to ‘hertz’ and ‘Hz’) 1/s unit of radioactivity; the activity of a quantity of material in which one nucleus decays per second (hence, equivalent to one unit per second) (SI derived unit with special names/symbols admitted for reasons of safeguarding human health) becquerel
bu 3.523907e-2 m ^3 unit of volume defined as 2150.42 cubic inches or 4 pecks in the US Customary system (and formerly in England), where it is used as a dry measure bushel
BV lg(re 1 V ) unit of electricity/magnetism
Bv lg(re 0.775 V ) unit of electricity/magnetism (rms voltage)
BW lg(re 1 W ) unit of power in decibel scale, referenced to 1 watt; the power in bel-watts is equal to 100 times the base 10 logarithm of the power in watts (making decibel-watt, the more common term, 10 times the base 10 log of the power in watts)
BZ lg(re (1e-6 m )^3) logarithmic unit used to compare the reflectivity (Z) of an unknown remote object, to the reflective return created by a droplet of rain with a diameter of 1 mm; is the base unit for “dBz”, which is the typical logarithmic unit for measuring atmospheric radar reflectivity; a value of 0 Bz (0 DBz) corresponds to the return from a single cubic micron; a value of 6 Bz (60 DBz) corresponds to extremely heavy rain.
BµV (uses MICRO SIGN) lg(re 1e-6 V ) unit of electricity/magnetism
C s .A standard unit of electric charge, the quantity of electricity transported in one second by a current of one ampere (SI derived unit) coulomb
cal 4.1868 J unit of heat energy used in thermochemistry, the International Steam Table (IT) calorie defined by the Fifth International Conference on the properties of Steam (1956) (exact) IT_calorie , calorie
cc cm ^3 unit of volume equal to the volume of a cube 1 centimeter on each side (exact)
cd Base SI unit The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540e12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. candela
Ci 3.7e10 Bq unit of radioactivity corresponding to 3.7 * 10e10 disintegrations per second (Unit is temporarily accepted for use with the SI.) curie
cm_H2O cm H2O unit of pressure derived from pressure head calculations using metrology; represents the pressure exerted by a column of water of 1 cm height at 4 degrees C cmH2O
cm_Hg cm Hg unit of pressure representing the pressure exerted by a column of mercury of 1 cm height at 0 degrees C cmHg
cmH2O cm H2O unit of pressure derived from pressure head calculations using metrology; represents the pressure exerted by a column of water of 1 cm height at 4 degrees C cm_H2O
cmHg cm Hg unit of pressure representing the pressure exerted by a column of mercury of 1 cm height at 0 degrees C cm_Hg
cps rotation /second unit of angular velocity (exact) rotation_per_second rps
d 24 h period of time equal to 24 hours day
dr avoirdupois_ounce /16 unit of mass in the avoirdupois system (the system commonly used in the United States) (exact) dram
DU 446.2 micromoles /meter ^2 dobson
e 1.602176487e-19 C unit of electricity/magnetism
eV 1.60217733e-19 J unit of energy equal to the work accelerating an electron through a potential difference of one volt (Unit’s value is obtained experimentally) electron_volt , electronvolt
F C /V standard unit of capacitance; the amount which, when a capacitor is charged to a potential difference of one volt, carries a charge of one coulomb (SI derived unit) farad
fldr US_fluid_ounce /8 unit of volume for liquid measure in the apothecary system, equal to 1/8 liquid ounce (exact) fluid_dram
floz US_liquid_gallon /128 unit of volume for liquid measure in the US Customary system, equal to 1/128 liquid gallon (exact) US_fluid_ounce , US_liquid_ounce , fluid_ounce , liquid_ounce oz
ft 12 international_inches unit of length equal to 12 international inches, in the imperial and US customary systems; primarily used in the United States foot , international_foot
ftH2O foot water unit of pressure representing the pressure exerted by a column of water of 1 foot height at 4 degrees C footH2O , foot_H2O , foot_water fth2o
fth2o foot water unit of pressure representing the pressure exerted by a column of water of 1 foot height at 4 degrees C footH2O , foot_H2O , foot_water ftH2O
g 1e-3 kg unit of mass equal to one thousandth of a kilogram (SI derived unit) gram
gf gram force unit of force, equal to the magnitude of the force exerted by one gram of mass in a 9.80665 m/s2 gravitational field (exact) force_gram , gram_force
gp gravity (exact) dynamic , geopotential
gr 6.479891e-5 kg unit of mass equal to 1/7000 pound grain
Gy J /kg unit of ionizing radiation, a measure of the absorbed dose of radiation; absorption of one joule of radiation energy by one kilogram of matter (SI derived unit with special names/symbols admitted for reasons of safeguarding human health) gray
h 60 min period of time equal to 60 minutes hour hr
H Wb /A unit of inductance; where a circuit’s current changes at a constant rate of 1 ampere per second, results in a generation of 1 V of potential difference (SI derived unit) henry
h2o gravity 1000 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of water (exact) conventional_water , water H2O
H2O gravity 1000 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of water (exact) conventional_water , water h2o
Hg gravity 13595.10 kg /m ^3 specifies the acceleration at the earth’s surface of a substance with the density of mercury at 0 degrees C conventional_mercury , mercury_0C , mercury_32F
hp 7.456999e2 W unit of power originally corresponding to the estimated typical power of draft horses, calculated as lifting 33000 pounds one foot in one minute (550 foot-pounds/second) (shaft_horsepower is a unit of power as delivered by a drive shaft at its output (e.g., of a ship, aircraft engine, or helicopter rotor; typically not automobiles due to drive train losses)) horsepower , shaft_horsepower
hr 60 min period of time equal to 60 minutes hour h
Hz 1/s unit of frequency meaning one cycle per second (SI derived unit) hertz
in 2.54 cm unit of length equal to 25.4 mm by definition, used in imperial and US customary systems inch , international_inch
in_Hg inch Hg unit of pressure representing the pressure exerted by a column of mercury of 1 inch height at 0 degrees C inch_Hg inHg
inHg inch Hg unit of pressure representing the pressure exerted by a column of mercury of 1 inch height at 0 degrees C inch_Hg in_Hg
J N .m standard unit of work or energy, equal to the work done by a force of one newton acting along a distance of one meter (SI derived unit) joule
K Base SI unit The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. kelvin
kat mol /s unit of catalytic activity (property of a catalyst, such as an enzyme); expresses the ability to break 1 mole of bonds per second under specified conditions (SI derived unit) katal
kg Base SI unit The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram. kilogram
kgf 9.806650 N unit of force, equal to the magnitude of the force exerted by one kilogram of mass in a 9.80665 m/s2 gravitational field (exact) force_kilogram , kilogram_force
ksi kip /in ^2 unit of pressure representing the pressure exerted, due to gravity, by a 1000-pound mass, of area one square inch (exact)
kt knot unit of speed, synonym for nautical_mile/hour (Synonym for SI unit) kts
kts knot unit of speed, synonym for nautical_mile/hour (Synonym for SI unit) kt
L (NIST recommendation) dm ^3 unit of capacity equal to 1000 cubic centimeters (The definition is exact. From 1901 to 1964, however, 1 liter was 1.000028 dm^3 (volume of 1 kg of water under standard conditions).) liter , litre l
l dm ^3 unit of capacity equal to 1000 cubic centimeters (The definition is exact. From 1901 to 1964, however, 1 liter was 1.000028 dm^3 (volume of 1 kg of water under standard conditions).) liter , litre L
lb 4.5359237e-1 kg unit of mass in avoirdupois system of weights (a system commonly used in United States) avoirdupois_pound , pound
lbf 4.4482216152605 N unit of force, equal to the magnitude of the force exerted by one pound of mass in a 9.80665 m/s2 gravitational field (exact) force_pound , pound_force
lm cd .sr unit of luminous flux, a measure of the total “amount” of visible light emitted by a source; one candela-steradian (SI derived unit) lumen
lx lm /m ^2 unit of illuminance and luminous emittance, measuring luminous flux per unit area, and used as a measure of intensity of light; equal to one lumen per square meter (SI derived unit) lux
m Base SI unit The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. meter , metre
mi 5280 international_feet unit of length equal to 5280 feet, equal to 12 international inches, in the imperial and US customary systems; primarily used in the United States and other smaller countries with ties to the US or United Kingdom international_mile , mile
min 60 s period of time equal to 60 seconds minute
mm_Hg mm Hg unit of pressure representing the pressure exerted by a column of mercury of 1 mm height at 0 degrees C; approximately (within 0.000015%, generally below measurement error) 1 Torr, which is 1/760 standard atmospheric pressure millimeter_Hg , torr mmHg , mm_hg , mmhg
mm_hg mm Hg unit of pressure representing the pressure exerted by a column of mercury of 1 mm height at 0 degrees C; approximately (within 0.000015%, generally below measurement error) 1 Torr, which is 1/760 standard atmospheric pressure millimeter_Hg , torr mmHg , mm_Hg , mmhg
mmhg mm Hg unit of pressure representing the pressure exerted by a column of mercury of 1 mm height at 0 degrees C; approximately (within 0.000015%, generally below measurement error) 1 Torr, which is 1/760 standard atmospheric pressure millimeter_Hg , torr mmHg , mm_Hg , mm_hg
mmHg mm Hg unit of pressure representing the pressure exerted by a column of mercury of 1 mm height at 0 degrees C; approximately (within 0.000015%, generally below measurement error) 1 Torr, which is 1/760 standard atmospheric pressure millimeter_Hg , torr mm_Hg , mm_hg , mmhg
mol Base SI unit The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles. mole
N m .kg /s ^2 unit of force; the amount needed to accelerate 1 kilogram of mass at the rate of 1 metre per second squared (SI derived unit) newton
nt 1 cd /m ^2 unit of illumination (exact) nit
Oe 7.957747e1 A /m unit of electricity/magnetism oersted
oz US_liquid_gallon /128 unit of volume for liquid measure in the US Customary system, equal to 1/128 liquid gallon (exact) US_fluid_ounce , US_liquid_ounce , fluid_ounce , liquid_ounce floz
ozf 2.780139e-1 N unit of force, equal to the magnitude of the force exerted by one ounce of mass in a 9.80665 m/s2 gravitational field (exact) force_ounce , ounce_force
Pa N /m ^2 unit of pressure (force per unit area) equal to one newton per square meter (SI derived unit) pascal
ph 1e4 lm /m ^2 unit of illumination (exact) phot
pk bushel /4 unit of volume defined as 537.6 cubic inches in the US Customary system (and formerly in England), where it is used as a dry measure (exact) peck
ppb 1e-9 parts per billion (Constant) ppbv
ppbv 1e-9 parts per billion (Constant) ppb
ppm 1e-6 parts per million (Constant) ppmv
ppmv 1e-6 parts per million (Constant) ppm
ppq 1e-15 parts per quadrillion (Constant) ppqv
ppqv 1e-15 parts per quadrillion (Constant) ppq
ppt 1e-12 parts per trillion (Constant) pptv
pptv 1e-12 parts per trillion (Constant) ppt
psi 1 pound gravity /in ^2 unit of pressure representing the pressure exerted, due to gravity, by a one-pound mass, of area one square inch; commonly referred to as “pounds per square inch” (exact)
pt US_liquid_gallon /8 unit of volume for liquid measure in the US Customary system, equal to 1/8 liquid gallon (exact) US_liquid_pint , liquid_pint , pint
PVU 1e-6 m ^2 s ^-1 K kg ^-1 (exact) potential_vorticity_unit
R 2.58e-4 C /kg unit of ionizing radiation, the amount producing one electrostatic unit of positive or negative ionic charge in one cubic centimeter of air under standard conditions; rarely used (Unit is temporarily accepted for use with the SI.) roentgen
rad Dimensionless quantity standard unit of angular measure, an angle that creates an arc in a circle equal in length to that circle’s radius (roughly 57.3 degrees); as a ratio of two lengths, it has no dimension (SI derived unit) radian
rpm rotation /minute unit of angular velocity measuring the angular distance covered by a rotating object, divided by the amount of time used to cover that distance; measured perpendicular to the plane of rotation, with direction usually indicated by the right-hand rule (exact)
rps rotation /second unit of angular velocity (exact) rotation_per_second cps
s Base SI unit The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. second
S A /V unit of electric conductance; the reciprocal of one ohm (SI derived unit) siemens
sb 1e4 cd /m ^2 unit of illumination (exact) stilb
sr rad ^2 standard unit of solid angle measure, it is the solid angle which cuts out an area on a sphere that is the square of the sphere’s radius; as a ratio of two areas, it has no dimension (SI derived unit) steradian
St 1e-4 m ^2/s unit of kinematic viscosity, measuring the ratio of the dynamic viscosity to the density of the fluid; water at 20 degrees C has a kinematic viscosity about 100 stokes, or more cmomonly, 1 cSt (exact) stokes
Sv J /kg unit of ionizing radiation dose, measuring the health effect of low levels of ionizing radiation on the human body (SI derived unit with special names/symbols admitted for reasons of safeguarding human health) sievert
t 1000 kg unit of weight equal to 1000 kilograms metric_ton , tonne
T Wb /m ^2 unit of flux density, equal to one weber per square meter (SI derived unit) tesla
Tbl US_fluid_ounce /2 unit of volume for liquid measure in the US Customary system, equal to 1/2 liquid ounce (exact) tablespoon Tblsp , Tbsp , tblsp , tbsp
tblsp US_fluid_ounce /2 unit of volume for liquid measure in the US Customary system, equal to 1/2 liquid ounce (exact) tablespoon Tbl , Tblsp , Tbsp , tbsp
Tblsp US_fluid_ounce /2 unit of volume for liquid measure in the US Customary system, equal to 1/2 liquid ounce (exact) tablespoon Tbl , Tbsp , tblsp , tbsp
tbsp US_fluid_ounce /2 unit of volume for liquid measure in the US Customary system, equal to 1/2 liquid ounce (exact) tablespoon Tbl , Tblsp , Tbsp , tblsp
Tbsp US_fluid_ounce /2 unit of volume for liquid measure in the US Customary system, equal to 1/2 liquid ounce (exact) tablespoon Tbl , Tblsp , tblsp , tbsp
thm 1.054804e8 J unit of energy legally defined in the U.S. Federal Register of July 27, 1968, and the legal unit used by the U.S. natural gas industry (exact) US_therm , therm
tsp tablespoon /3 unit of volume defined as 1/3 tablespoon, the actual volume of which can vary depending on the measurement system (but is based on the US Customary system in this database) (exact) teaspoon
u 1.6605402e-27 kg standard unit for indicating mass on an atomic or molecular scale; is approximately the mass of one nucleon (either a single proton or neutron), and equivalent to 1 g/mol (Unit’s value is obtained experimentally) amu , atomic_mass_unit , atomicmassunit , unified_atomic_mass_unit
ua 1.495979e11 m unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun (Unit’s value is obtained experimentally) astronomical_unit
V W /A standard unit of electric potential difference (and electromotive force); the difference of potential between two points of a conductor carrying a constant current of one ampere and dissipating one watt of power (SI derived unit) volt
VA V .A unit of electric power equal to the product of one volt and one ampere, equivalent to one watt for direct current systems and a unit of apparent power for alternating current systems (exact) voltampere
W J /s standard unit of power, equivalent to one joule per second, and equal to one ampere flowing across a potential difference of one volt (SI derived unit) watt
Wb V .s unit of magnetic flux (product of the average magnetic field times the perpendicular area that it penetrates), expressed as volt-seconds (SI derived unit) weber
yd 3 international_feet unit of length equal to 3 international feet, in the imperial and US customary systems; primarily used in the United States international_yard , yard
yr 3.15569259747e7 s unit of time; Interval between 2 successive passages of sun through vernal equinox (365.242198781 days). See http://www.ast.cam.ac.uk/pubinfo/leaflets/, http://aa.usno.navy.mil/AA/, and http://adswww.colorado.edu/adswww/astro_coord.html tropical_year , year
° (DEGREE SIGN) (pi /180) rad measurement of a plane angle representing 1/360 of a full rotation angular_degree , arc_degree , arcdeg , degree
°C (DEGREE SIGN) K @ 273.15 unit (and scale) of temperature, with same magnitude as the kelvin and a zero-point offset of 273.15 (SI derived unit) degree_Celsius
°F (DEGREE SIGN) °R @ 459.67 unit of thermodynamic temperature degF , deg_F , degreeF , degree_F , degree_fahrenheit , fahrenheit
°K (DEGREE SIGN) K unit of temperature, synonym for kelvin (Synonym for SI unit) degK , deg_K , degreeK , degree_K , degree_kelvin
°R (DEGREE SIGN) K /1.8 unit of thermodynamic temperature degR , deg_R , degreeR , degree_R , degree_rankine
Å (LATIN CAPITAL LETTER A WITH RING ABOVE) 1e-10 m unit of length equal to one hundred-millionth of a centimeter (1 meter/10**10) (Unit is temporarily accepted for use with the SI.) ångström , angstrom
Å (ANGSTROM SIGN) 1e-10 m unit of length equal to one hundred-millionth of a centimeter (1 meter/10**10) (Unit is temporarily accepted for use with the SI.) ångström , angstrom Å
π (GREEK SMALL LETTER PI) 3.141592653589793238462643383279 mathematical constant equal to the ratio of a circle’s circumference to its diameter (This “unit” is useful in the definition of subsequent units.) pi
Ω (OHM SIGN) V /A standard unit of electrical resistance; the resistance between two points of a conductor when a constant potential difference of 1.0 volt, applied to these points, produces in the conductor a current of 1.0 ampere (SI derived unit) ohm Ω
Ω (Greek capital letter omega (preferred)) V /A standard unit of electrical resistance; the resistance between two points of a conductor when a constant potential difference of 1.0 volt, applied to these points, produces in the conductor a current of 1.0 ampere (SI derived unit) ohm
′ (PRIME) ° /60 measurement of a plane angle equal to 1/60 arc degree angular_minute , arc_minute , arcmin , arcminute
″ (DOUBLE PRIME) /60 measurement of a plane angle equal to 1/60 arc minute angular_second , arc_second , arcsec , arcsecond
℃ (DEGREE CELSIUS) degree_Celsius unit of temperature, synonym for ‘K @ 273.15’ (degree_Celsius) (Synonym for SI unit) celsius , degC , deg_C , degreeC , degree_C
℉ (DEGREE FAHRENHEIT) °R @ 459.67 unit of thermodynamic temperature degF , deg_F , degreeF , degree_F , degree_fahrenheit , fahrenheit °F

## Unit Prefixes

yotta 1e24 Y
zetta 1e21 Z
exa 1e18 E
peta 1e15 P
tera 1e12 T
giga 1e9 G
mega 1e6 M
kilo 1e3 k
hecto 100 h
deka 10 da
deci .1 d
centi .01 c
milli 1e-3 m
micro 1e-6 µ
μ
u
MICRO SIGN
Greek small letter ‘mu’
nano 1e-9 n
pico 1e-12 p
femto 1e-15 f
atto 1e-18 a
zepto 1e-21 z
yocto 1e-24 y