60 s
minute
min period of time equal to 60 seconds
60 min
hour
h hr period of time equal to 60 minutes
24 h
day
d period of time equal to 24 hours
This "unit" is useful in the definition of subsequent units.
3.141592653589793238462643383279
pi
π
mathematical constant equal to the ratio of a circle's circumference to its diameter
(pi/180) rad
arc_degree
° angular_degree degree arcdeg measurement of a plane angle representing 1/360 of a full rotation
°/60
arc_minute
' ′ angular_minute arcminute arcmin measurement of a plane angle equal to 1/60 arc degree
'/60
arc_second
" ″ angular_second arcsecond arcsec measurement of a plane angle equal to 1/60 arc minute
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).
dm^3
liter
L litre l unit of capacity equal to 1000 cubic centimeters
1000 kg
metric_ton
t tonne unit of weight equal to 1000 kilograms
Unit's value is obtained experimentally
1.60217733e-19 J
electronvolt
eV electron_volt unit of energy equal to the work accelerating an electron through a potential difference of one volt
Unit's value is obtained experimentally
1.6605402e-27 kg
unified_atomic_mass_unit
u atomic_mass_unit atomicmassunit amu 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
According to resolution by the International Astronomical Union (IAU) in 2012
1.49597870700e11 m
astronomical_unit
au
Exact definition according to 2012 resolution by the International Astronomical Union (IAU). Ostensibly equal to the mean distance from the center of the earth to the center of the sun.
Pre-2012 resolution by the IAU
1.495979e11 m
astronomical_unit_BIPM_2006
ua
unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun according to the International Bureau of Weights and Measures (BIPM) in 2006
Unit is temporarily accepted for use with the SI.
1852 m
nautical_mile
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.
nautical_mile/hour
international_knot
knot_international
knot
derived unit of speed at sea
Unit is temporarily accepted for use with the SI.
1e-10 m
angstrom
ångström
Å Å
unit of length equal to one hundred-millionth of a centimeter (1 meter/10**10)
Unit is temporarily accepted for use with the SI.
dam^2
are
a
unit of area equal to 100 square meters
Unit is temporarily accepted for use with the SI.
100 are
hectare
unit of area equal to 100 are ('hectoare'), or 10000 square meters
Unit is temporarily accepted for use with the SI.
100 fm^2
barn
b
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.
1000 hPa
bar
unit of pressure equal to 100000 Pascals, or about 0.987 atmospheres of pressure
Unit is temporarily accepted for use with the SI.
cm/s^2
gal
unit of acceleration equal to 1 cm per second squared
Unit is temporarily accepted for use with the SI.
3.7e10 Bq
curie
Ci
unit of radioactivity corresponding to 3.7 * 10e10 disintegrations per second
Unit is temporarily accepted for use with the SI.
2.58e-4 C/kg
roentgen
R
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.
cSv
rem
unit of radiation dosage applied to humans; equal to one hundredth of a sievert
meter
m metre 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.
kilogram
kg The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram.
second
s 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.
ampere
A 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.
kelvin
K The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
mole
mol 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.
candela
cd 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.
Synonym for SI unit
s
sec
unit of time, synonym for second
Synonym for SI unit
A
amp
unit of electric current, synonym for ampere
Synonym for SI unit
K
°K degree_kelvin degrees_kelvin degree_K degrees_K degreeK degreesK deg_K degs_K degK degsK
unit of temperature, synonym for kelvin
Synonym for SI unit
cd
candle
unit of luminous intensity, synonym for candela
Synonym for SI unit
mole
einstein
unit of chemical mass, synonym for mole
Synonym for SI unit
Hz
baud
Bd bps
unit of frequency, synonym for hertz
Synonym for SI unit
degree_Celsius
℃ celsius degree_C degrees_C degreeC degreesC deg_C degs_C degC degsC
unit of temperature, synonym for 'K @ 273.15' (degree_Celsius)
Synonym for SI unit
knot
kt kts
unit of speed, synonym for nautical_mile/hour
Constant; value is +-30e15
6.02214179e23/mol
avogadro_constant
number of constituent particles (usually atoms or molecules) per mole of a given substance
Constant
0.01
percent
%
number of parts per hundred
Constant
1
ppv
parts per volume
Constant
1e-6
ppm ppmv
parts per million
Constant
1e-9
ppb ppbv
parts per billion
Constant
1e-12
ppt pptv
parts per trillion
Constant
1e-15
ppq ppqv
parts per quadrillion
0.9 arc_degree
grade
1/100 of a right angle (90 degrees)
2 pi rad
circle
cycle
turn
revolution
rotation
unit of angle in a plane signifying a full 360-degree circle
arc_degree
degree_north
degrees_north
degree_N
degrees_N
degreeN
degreesN
degree_east
degrees_east
degree_E
degrees_E
degreeE
degreesE
degree_true
degrees_true
degree_T
degrees_T
degreeT
degreesT
unit of angle on a sphere
-1 degree_east
degree_west
degrees_west
degree_W
degrees_W
degreeW
degreesW
unit of angle on a sphere (units for negative direction)
2.916667e-2 kg
assay_ton
reference unit of mass for a body of ore; roughly equal to 29167 milligrams
2.834952e-2 kg
avoirdupois_ounce
unit of mass equal to 1/16 avoirdupois pound, commonly used in the United States (16 oz = 1 pound = 7000 grains)
4.5359237e-1 kg
avoirdupois_pound
pound
lb
unit of mass in avoirdupois system of weights (a system commonly used in United States)
2e-4 kg
carat
unit of mass equal to 0.2 gram (defined 1907)
6.479891e-5 kg
grain
gr
unit of mass equal to 1/7000 pound
5.080235e1 kg
long_hundredweight
unit of mass; a British hundredweight, which is 8 stone * 14 pounds/stone
1.555174e-3 kg
pennyweight
unit of mass; based on historical US troy weight system (is 1/20 troy ounce)
4.535924e1 kg
short_hundredweight
unit of mass, a US hundredweight, which is 100 pounds
14.59390 kg
slug
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
3.110348e-2 kg
troy_ounce
apothecary_ounce
unit of mass; based on historical US troy weight system (is 1/12 troy pound)
3.732417e-1 kg
troy_pound
apothecary_pound
unit of mass; based on historical US troy weight system (is 5760 grain)
20 grain
scruple
unit of mass in apothecaries' weight system (is 1/3 apdram)
60 grain
apdram
unit of mass in apothecaries' weight system (is 1/8 apounce)
exact
avoirdupois_ounce/16
dram
dr
unit of mass in the avoirdupois system (the system commonly used in the United States)
480 grain
apounce
unit of mass in apothecaries' weight system (is 1/16 appound)
5760 grain
appound
unit of mass in apothecaries' weight system (is same as a troy pound)
94 pound
bag
unit of mass, for a traditional bag of portland cement
2000 pound
short_ton
ton
unit of mass based on US weight system
2240 pound
long_ton
unit of mass based on British imperial weight system
1e-15 m
fermi
unit of length equal to 10e-15 meters, a typical length-scale of nuclear physics
9.46073e15 m
light_year
unit of length equal to the distance traversed by light in one mean solar year (365.2422 days), a typical length-scale of astronomy
1e-6 m
micron
unit of length, a typical length-scale of technology and science fields
2.54e-5 m
mil
unit of length equal to 0.001 inch, a typical length-scale for measuring wire diameters
3.085678e16 m
parsec
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
3.514598e-4 m
printers_point
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)
2.011684e1 m
chain
unit of length equal to 66 feet (4 poles), or 1/10 furlong, a typical (historical) scale of land surveying
12 printers_point
printers_pica
pica
unit of length equal to 1/6 inch (12 printers points)
nautical_mile
nmile
unit of length in the US Customary System, equal to 6,076 feet; typically used for air and sea navigation
(1200/3937) m
US_survey_foot
US_survey_feet
unit of length used for earlier survey data in some countries, slightly different than the current international foot
3 US_survey_feet
US_survey_yard
unit of length used in earlier survey data in some countries, slightly different than the current international yard
5280 US_survey_feet
US_survey_mile
US_statute_mile
unit of length used for earlier survey data in some countries, slightly slightly different than the current international mile
16.5 US_survey_feet
rod
pole
perch
unit of length equal to one-fourth of a surveyor's chain
660 US_survey_feet
furlong
unit of length equal to 1/8 mile or 10 chains
6 US_survey_feet
fathom
unit of length equal to 6 feet in the imperial and US customary systems, typically used for measuring depth of water
2.54 cm
international_inch
inch
in
unit of length equal to 25.4 mm by definition, used in imperial and US customary systems
12 international_inches
international_foot
international_feet
foot
feet
ft
unit of length equal to 12 international inches, in the imperial and US customary systems; primarily used in the United States
3 international_feet
international_yard
yard
yd
unit of length equal to 3 international feet, in the imperial and US customary systems; primarily used in the United States
5280 international_feet
international_mile
mile
mi
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
inch/72
big_point
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)
inch/3
barleycorn
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
191.835 foot
arpentlin
unit of length in French regions; a linear arpent is of length 10 perch (10 rod)
exact
rotation/second
rotation_per_second
rotations_per_second
rps cps
unit of angular velocity
exact
rotation/minute
rpm
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
1.111111e-7 kg/m
denier
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
exact
1e-6 kg/m
tex
unit of lineic mass density for fibers, defined as mass in grams per 1000 meters (more common in Canada and Continental Europe)
5.72135e-11 kg/(Pa.s.m^2)
perm_0C
perms_0C
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
5.74525e-11 kg/(Pa.s.m^2)
perm_23C
perms_23C
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
5.067075e-10 m^2
circular_mil
unit of area equal to the area of a one-mil diameter circle
porous solid permeability
9.869233e-13 m^2
darcy
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
exact
160 rod^2
acre
unit of area in the US Customary System, used in land and sea floor measurement, equal to 43560 square feet
An "acre.foot", however, is 1233.4867714897 m^3. Odd.
1.233489e3 m^3
acre_foot
acre_feet
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
2.359737e-3 m^3
board_foot
board_feet
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
3.523907e-2 m^3
bushel
bu
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
exact
bushel/4
peck
pk
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
4.546090e-3 m^3
Canadian_liquid_gallon
unit of volume for liquids in the Imperial system
4.404884e-3 m^3
US_dry_gallon
unit of volume for dry measure in the US Customary system, defined as 1/2 peck or 1/8 bushel
exact
cm^3
cc
unit of volume equal to the volume of a cube 1 centimeter on each side
exact
1 m^3
stere
unit of volume equal to a cubic meter, originally defined primarily as a measure for firewood
2.831685 m^3
register_ton
unit of volume used for internal capacity of ships, equal to 100 cubic feet
exact
US_dry_gallon/4
US_dry_quart
dry_quart
unit of volume for dry measure in the US Customary system, equal to 1/32 US bushel
exact
US_dry_gallon/8
US_dry_pint
dry_pint
unit of volume for dry measure in the US Customary system, equal to 1/2 US dry quart
3.785412e-3 m^3
US_liquid_gallon
liquid_gallon
gallon
unit of volume for liquid measure in the US Customary system, defined as 3.785412 liters
The following is the definition of the petroleum industry
42 US_liquid_gallon
barrel
bbl
unit of volume used by US and Canadian petroleum organizations
The following is exact regardless of the definition of "barrel"
barrel/4
firkin
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
exact
US_liquid_gallon/4
US_liquid_quart
liquid_quart
quart
unit of volume for liquid measure in the US Customary system, equal to 1/4 liquid gallon
exact
US_liquid_gallon/8
US_liquid_pint
liquid_pint
pint
pt
unit of volume for liquid measure in the US Customary system, equal to 1/8 liquid gallon
exact
US_liquid_gallon/16
US_liquid_cup
liquid_cup
cup
unit of volume for liquid measure in the US Customary system, equal to 1/16 liquid gallon
exact
US_liquid_gallon/32
US_liquid_gill
liquid_gill
gill
unit of volume for liquid measure in the US Customary system, equal to 1/32 liquid gallon
exact
US_liquid_gallon/128
US_fluid_ounce
US_liquid_ounce
fluid_ounce
liquid_ounce
oz floz
unit of volume for liquid measure in the US Customary system, equal to 1/128 liquid gallon
exact
US_fluid_ounce/2
tablespoon
Tbl Tbsp tbsp Tblsp tblsp
unit of volume for liquid measure in the US Customary system, equal to 1/2 liquid ounce
exact
US_fluid_ounce/8
fluid_dram
fldr
unit of volume for liquid measure in the apothecary system, equal to 1/8 liquid ounce
exact
tablespoon/3
teaspoon
tsp
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
4.546090e-3 m^3
UK_liquid_gallon
unit of volume for liquid measure in the Imperial system
exact
UK_liquid_gallon/4
UK_liquid_quart
unit of volume for liquid measure in the Imperial system, equal to 1/4 liquid gallon
exact
UK_liquid_gallon/8
UK_liquid_pint
unit of volume for liquid measure in the Imperial system, equal to 1/8 liquid gallon
exact
UK_liquid_gallon/16
UK_liquid_cup
unit of volume for liquid measure in the Imperial system, equal to 1/16 liquid gallon
exact
UK_liquid_gallon/32
UK_liquid_gill
unit of volume for liquid measure in the Imperial system, equal to 1/32 liquid gallon
exact
UK_liquid_gallon/160
UK_fluid_ounce
UK_liquid_ounce
unit of volume for liquid measure in the Imperial system, equal to 1/160 liquid gallon
lg(re (1e-6 m)^3)
BZ
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.
1e-8 s
shake
unit of time approximating the lifetime of an individual neutron, useful for describing very brief durations, e.g., in nuclear physics
8.616409e4 s
sidereal_day
unit of time that it takes the earth to complete one revolution with respect to a star, roughly 23 hours, 56 minutes, 4 seconds
3.590170e3 s
sidereal_hour
unit of time equal to 1/24 sidereal day
5.983617e1 s
sidereal_minute
unit of time equal to 1/60 sidereal hour
0.9972696 s
sidereal_second
unit of time equal to 1/60 sidereal minute
3.155815e7 s
sidereal_year
unit of time for the earth to make one complete revolution around the sun, relative to the fixed stars
3.15569259747e7 s
tropical_year
year
yr
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
29.530589 day
lunar_month
unit of time equal to the average time between successive new or full moons; equal to approximately 29 days, 12 hours, 44 minutes
365 day
common_year
unit of time corresponding to a 'normal' calendar year, that is, one without insertion of a leap day
366 day
leap_year
unit of time corresponding to a calendar year with a leap day inserted
365.25 day
Julian_year
unit of time recognized by the International Astronomical Union for use in astronomy, defined as 365.25 days of 86400 seconds
365.2425 day
Gregorian_year
unit of time based on the Gregorian Calendar, the one commonly used today; approximates the tropical year as 365 + 97/400 days
27.321661 day
sidereal_month
unit of time based on 1/12 of the sidereal year
27.321582 day
tropical_month
unit of time based on 1/12 of the tropical year
14 day
fortnight
unit of time commonly defined as 14 days
7 day
week
unit of time commonly defined as 7 days
multiple values have been proposed for the amount of time represented by a 'jiffy'
0.01 s
jiffy
unit of time used in computer animation as a method of defining playback rate
1e9 year
eon
unit of time defined in astronomy as 1 billion years
year/12
month
unit of time defined as the average length of time for a calendar month
exact
1e6 m^3/s
sverdrup
unit of volume transport, used almost exclusively to measure the volumetric rate of ocean currents
exact
9.806650 m/s^2
standard_free_fall
unit of acceleration corresponding to the nominal gravitational acceleration of an object in a vacuum near the surface of earth
should be local
standard_free_fall
gravity
unit of acceleration synonymous with standard rate of free fall (in earth's gravity)
exact
gravity 1000 kg/m^3
conventional_water
water
H2O h2o
specifies the acceleration at the earth's surface of a substance with the density of water
gravity 999.972 kg/m^3
water_4C
waters_4C
water_39F
waters_39F
specifies the acceleration at the earth's surface of a substance with the density of water at 4 degrees C
gravity 999.001 kg/m^3
water_60F
waters_60F
specifies the acceleration at the earth's surface of a substance with the density of water at 60 degrees F
gravity 13595.10 kg/m^3
mercury_0C
mercuries_0C
mercury_32F
mercuries_32F
conventional_mercury
conventional_mercuries
Hg
specifies the acceleration at the earth's surface of a substance with the density of mercury at 0 degrees C
gravity 13556.8 kg/m^3
mercury_60F
mercuries_60F
specifies the acceleration at the earth's surface of a substance with the density of mercury at 60 degrees F
standard_free_fall
force
unit of force equivalent to the force generated by the effect of gravity
exact
1e-5 N
dyne
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
9.806650e-3 N
pond
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
9.806650 N
force_kilogram
kilogram_force
kilograms_force
kgf
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
2.780139e-1 N
force_ounce
ounce_force
ounces_force
ozf
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
4.4482216152605 N
force_pound
pound_force
pounds_force
lbf
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
1.382550e-1 N
poundal
unit of force, that which is necessary to accelerate 1 pound-mass to 1 foot per second per second
exact
gram force
gram_force
grams_force
force_gram
gf
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
2000 force_pound
force_ton
ton_force
tons_force
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
1000 lbf
kip
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
1.01325e5 Pa
standard_atmosphere
atmosphere
atm
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; note that the symbol 'at' clashes with that of the katal ('kat'), the SI unit of catalytic activity
1 kg gravity/cm2
technical_atmosphere
at
unit of pressure equal to one kilogram force per square centimeter
cm H2O
cm_H2O cmH2O
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
exact
inch water_39F
inch_H2O_39F
inches_H2O_39F
unit of pressure representing the pressure exerted by a column of water of 1 inch height at 39 degrees F
exact
inch water_60F
inch_H2O_60F
inches_H2O_60F
unit of pressure representing the pressure exerted by a column of water of 1 inch height at 60 degrees F
foot water
foot_water
feet_water
foot_H2O
feet_H2O
footH2O
feetH2O
ftH2O fth2o
unit of pressure representing the pressure exerted by a column of water of 1 foot height at 4 degrees C
cm Hg
cm_Hg cmHg
unit of pressure representing the pressure exerted by a column of mercury of 1 cm height at 0 degrees C
exact
mm mercury_0C
millimeter_Hg_0C
millimeters_Hg_0C
unit of pressure representing the pressure exerted by a column of mercury of 1 mm height at 0 degrees C
exact
inch mercury_32F
inch_Hg_32F
inches_Hg_32F
unit of pressure representing the pressure exerted by a column of mercury of 1 inch height at 32 degrees F
exact
inch mercury_60F
inch_Hg_60F
inches_Hg_60F
unit of pressure representing the pressure exerted by a column of mercury of 1 inch height at 60 degrees F
mm Hg
millimeter_Hg
millimeters_Hg
torr
mm_Hg mm_hg mmHg mmhg
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
inch Hg
inch_Hg
inches_Hg
in_Hg inHg
unit of pressure representing the pressure exerted by a column of mercury of 1 inch height at 0 degrees C
exact
1 pound gravity/in^2
psi
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
kip/in^2
ksi
unit of pressure representing the pressure exerted, due to gravity, by a 1000-pound mass, of area one square inch
exact
0.1 N/m^2
barie
barye
unit of pressure equal to one dyne per square centimeter
sound pressure level
lg(re 20e-6 Pa)
B_SPL
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)
exact
1e-1 Pa.s
poise
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
1e-4 m^2/s
stokes
St
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
10/(Pa.s)
rhe
unit of fluidity (reciprocal of velocity), measured in reciprocal poise
exact
1e-7 J
erg
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
1.05505585262e3 J
IT_Btu
IT_Btus
Btu
Btus
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 (reference NIST Guide to SI Units)
1.05506e8 J
EC_therm
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
4.184000 J
thermochemical_calorie
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
4.1868 J
IT_calorie
calorie
cal
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)
by definition
4.184 MJ/kg
TNT
unit of energy; approximately the energy released by the detonation of a given amount of mass of TNT
by definition
4.184e9 J
ton_TNT
tons_TNT
unit of energy; approximately the energy released by the detonation of a 1000 kilograms of TNT
exact
1.054804e8 J
US_therm
therm
thm
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
watt.hour
watthour
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
1e9 eV
bev
unit of energy corresponding to 1 billion electron volts (eV)
exact
V.A
voltampere
VA
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
9.80950e3 W
boiler_horsepower
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
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)
7.456999e2 W
shaft_horsepower
horsepower
hp
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)
7.35499e2 W
metric_horsepower
unit of power corresponding to a calculation of 75 kilogram-meters/second
exact
7.460000e2 W
electric_horsepower
unit of power defined in the International System of Units as exactly 746 W; generally used for power used by electrical machines
7.46043e2 W
water_horsepower
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.
7.4570e2 W
UK_horsepower
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
12000 Btu/hr
refrigeration_ton
ton_of_refrigeration
tons_of_refrigeration
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
lg(re 1 W)
BW
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)
lg(re 1 mW)
Bm
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 milliwatts)
1.55e-1 K.m^2/W
clo
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%
10 A
abampere
basic unit of electricity in the electromagnetic CGS system of units
7.957747e-1 A
gilbert
unit of electricity/magnetism
3.335640e-10 A
statampere
unit of electricity/magnetism
10 A
biot
basic unit of electricity in the electromagnetic CGS system of units (same as abampere), named after Jean-Baptiste Biot
exact
1e9 F
abfarad
unit of electricity/magnetism
exact
1e-9 H
abhenry
unit of electricity/magnetism
exact
1e9 S
abmho
unit of electricity/magnetism
exact
1e-9 ohm
abohm
unit of electricity/magnetism
exact
1e-8 V
abvolt
unit of electricity/magnetism
1.602176487e-19 C
e
unit of electricity/magnetism
9.64957e4 C
chemical_faraday
unit of electricity/magnetism
9.65219e4 C
physical_faraday
unit of electricity/magnetism
9.648531e4 C
C12_faraday
faraday
unit of electricity/magnetism
exact
1e-9 T
gamma
unit of electricity/magnetism
exact
1e-4 T
gauss
unit of electricity/magnetism
exact
1e-8 Wb
maxwell
unit of electricity/magnetism
7.957747e1 A/m
oersted
Oe
unit of electricity/magnetism
3.335640e-10 C
statcoulomb
unit of electricity/magnetism
1.112650e-12 F
statfarad
unit of electricity/magnetism
8.987554e11 H
stathenry
unit of electricity/magnetism
1.112650e-12 S
statmho
unit of electricity/magnetism
8.987554e11 ohm
statohm
unit of electricity/magnetism
2.997925e2 V
statvolt
unit of electricity/magnetism
1.256637e-7 Wb
unit_pole
unit of electricity/magnetism
lg(re 1 V)
BV
unit of electricity/magnetism
rms voltage
lg(re 0.775 V)
Bv
unit of electricity/magnetism
lg(re 1e-6 V)
BµV
unit of electricity/magnetism
K/1.8
°R degree_rankine degrees_rankine degreeR degreesR degree_R degrees_R degR degsR deg_R degs_R
unit of thermodynamic temperature
°R @ 459.67
°F ℉ fahrenheit degree_fahrenheit degrees_fahrenheit degreeF degreesF degree_F degrees_F degF degsF deg_F degs_F
unit of thermodynamic temperature
1.076391e-1 lx
footcandle
unit of illumination
exact
3.426259 cd/m^2
footlambert
unit of illumination
exact
(1e4/pi) cd/m^2
lambert
unit of illumination
exact
1e4 cd/m^2
stilb
sb
unit of illumination
exact
1e4 lm/m^2
phot
ph
unit of illumination
exact
1 cd/m^2
nit
nt
unit of illumination
exact
4.184000e4 J/m^2
langley
unit of illumination
exact
cd/(pi m^2)
blondel
apostilb
unit of illumination
exact
100/m
kayser
exact
gravity
geopotential
dynamic
gp
exact
2056 hours
work_year
exact
work_year/12
work_month
exact
1e-6 m^2 s^-1 K kg^-1
potential_vorticity_unit
PVU
1
count
1
bit
8
octet
byte
446.2 micromoles/meter^2
dobson
DU
1/avogadro_constant
molecule
molec
nucleon
nuc
SI derived unit
radian
rad 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^2
steradian
sr 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
1/s
hertz
Hz unit of frequency meaning one cycle per second
SI derived unit
1e-3 kg
gram
g unit of mass equal to one thousandth of a kilogram
SI derived unit
m.kg/s^2
newton
N 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/m^2
pascal
Pa unit of pressure (force per unit area) equal to one newton per square meter
SI derived unit
N.m
joule
J 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/s
watt
W 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
s.A
coulomb
C standard unit of electric charge, the quantity of electricity transported in one second by a current of one ampere
SI derived unit
W/A
volt
V 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
C/V
farad
F 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
V/A
ohm
Ω Ω 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
A/V
siemens
S unit of electric conductance; the reciprocal of one ohm
SI derived unit
V.s
weber
Wb 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/m^2
tesla
T unit of flux density, equal to one weber per square meter
SI derived unit
Wb/A
henry
H 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
K @ 273.15
degree_Celsius
degrees_Celsius
°C unit (and scale) of temperature, with same magnitude as the kelvin and a zero-point offset of 273.15
SI derived unit
cd.sr
lumen
lm unit of luminous flux, a measure of the total "amount" of visible light emitted by a source; one candela-steradian
SI derived unit
lm/m^2
lux
lx 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
mol/s
katal
kat 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 with special names/symbols admitted for reasons of safeguarding human health
1/s
becquerel
Bq
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
J/kg
gray
Gy 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
J/kg
sievert
Sv
unit of ionizing radiation dose, measuring the health effect of low levels of ionizing radiation on the human body
1e24
yotta
Y
1e21
zetta
Z
1e18
exa
E
1e15
peta
P
1e12
tera
T
1e9
giga
G
1e6
mega
M
1e3
kilo
k
100
hecto
h
10
deka
da
.1
deci
d
.01
centi
c
1e-3
milli
m
1e-6
micro
µ μ u
1e-9
nano
n
1e-12
pico
p
1e-15
femto
f
1e-18
atto
a
1e-21
zepto
z
1e-24
yocto
y
udunits2-prefixes.xml
udunits2-base.xml
udunits2-derived.xml
udunits2-accepted.xml
udunits2-common.xml