Constants (scipy.constants)

Physical and mathematical constants and units.

Mathematical constants

pi	Pi
golden	Golden ratio
golden_ratio	Golden ratio

Physical constants

c	speed of light in vacuum
speed_of_light	speed of light in vacuum
mu_0	the magnetic constant \(\mu_0\)
epsilon_0	the electric constant (vacuum permittivity), \(\epsilon_0\)
h	the Planck constant \(h\)
Planck	the Planck constant \(h\)
hbar	\(\hbar = h/(2\pi)\)
G	Newtonian constant of gravitation
gravitational_constant	Newtonian constant of gravitation
g	standard acceleration of gravity
e	elementary charge
elementary_charge	elementary charge
R	molar gas constant
gas_constant	molar gas constant
alpha	fine-structure constant
fine_structure	fine-structure constant
N_A	Avogadro constant
Avogadro	Avogadro constant
k	Boltzmann constant
Boltzmann	Boltzmann constant
sigma	Stefan-Boltzmann constant \(\sigma\)
Stefan_Boltzmann	Stefan-Boltzmann constant \(\sigma\)
Wien	Wien displacement law constant
Rydberg	Rydberg constant
m_e	electron mass
electron_mass	electron mass
m_p	proton mass
proton_mass	proton mass
m_n	neutron mass
neutron_mass	neutron mass

Constants database

In addition to the above variables, scipy.constants also contains the 2018 CODATA recommended values [CODATA2018] database containing more physical constants.

value(key)	Value in physical_constants indexed by key
unit(key)	Unit in physical_constants indexed by key
precision(key)	Relative precision in physical_constants indexed by key
find([sub, disp])	Return list of physical_constant keys containing a given string.
ConstantWarning	Accessing a constant no longer in current CODATA data set

scipy.constants.physical_constants

Dictionary of physical constants, of the format physical_constants[name] = (value, unit, uncertainty).

Available constants:

alpha particle mass	6.6446573357e-27 kg
alpha particle mass energy equivalent	5.9719201914e-10 J
alpha particle mass energy equivalent in MeV	3727.3794066 MeV
alpha particle mass in u	4.001506179127 u
alpha particle molar mass	0.0040015061777 kg mol^-1
alpha particle relative atomic mass	4.001506179127
alpha particle-electron mass ratio	7294.29954142
alpha particle-proton mass ratio	3.97259969009
Angstrom star	1.00001495e-10 m
atomic mass constant	1.6605390666e-27 kg
atomic mass constant energy equivalent	1.4924180856e-10 J
atomic mass constant energy equivalent in MeV	931.49410242 MeV
atomic mass unit-electron volt relationship	931494102.42 eV
atomic mass unit-hartree relationship	34231776.874 E_h
atomic mass unit-hertz relationship	2.25234271871e+23 Hz
atomic mass unit-inverse meter relationship	751300661040000.0 m^-1
atomic mass unit-joule relationship	1.4924180856e-10 J
atomic mass unit-kelvin relationship	10809540191600.0 K
atomic mass unit-kilogram relationship	1.6605390666e-27 kg
atomic unit of 1st hyperpolarizability	3.2063613061e-53 C^3 m^3 J^-2
atomic unit of 2nd hyperpolarizability	6.2353799905e-65 C^4 m^4 J^-3
atomic unit of action	1.054571817e-34 J s
atomic unit of charge	1.602176634e-19 C
atomic unit of charge density	1081202384570.0 C m^-3
atomic unit of current	0.00662361823751 A
atomic unit of electric dipole mom.	8.4783536255e-30 C m
atomic unit of electric field	514220674763.0 V m^-1
atomic unit of electric field gradient	9.7173624292e+21 V m^-2
atomic unit of electric polarizability	1.64877727436e-41 C^2 m^2 J^-1
atomic unit of electric potential	27.211386245988 V
atomic unit of electric quadrupole mom.	4.4865515246e-40 C m^2
atomic unit of energy	4.3597447222071e-18 J
atomic unit of force	8.2387234983e-08 N
atomic unit of length	5.29177210903e-11 m
atomic unit of mag. dipole mom.	1.85480201566e-23 J T^-1
atomic unit of mag. flux density	235051.756758 T
atomic unit of magnetizability	7.8910366008e-29 J T^-2
atomic unit of mass	9.1093837015e-31 kg
atomic unit of momentum	1.9928519141e-24 kg m s^-1
atomic unit of permittivity	1.11265005545e-10 F m^-1
atomic unit of time	2.4188843265857e-17 s
atomic unit of velocity	2187691.26364 m s^-1
Avogadro constant	6.02214076e+23 mol^-1
Bohr magneton	9.2740100783e-24 J T^-1
Bohr magneton in eV/T	5.788381806e-05 eV T^-1
Bohr magneton in Hz/T	13996244936.1 Hz T^-1
Bohr magneton in inverse meter per tesla	46.686447783 m^-1 T^-1
Bohr magneton in K/T	0.67171381563 K T^-1
Bohr radius	5.29177210903e-11 m
Boltzmann constant	1.380649e-23 J K^-1
Boltzmann constant in eV/K	8.617333262e-05 eV K^-1
Boltzmann constant in Hz/K	20836619120.0 Hz K^-1
Boltzmann constant in inverse meter per kelvin	69.50348004 m^-1 K^-1
classical electron radius	2.8179403262e-15 m
Compton wavelength	2.42631023867e-12 m
conductance quantum	7.748091729e-05 S
conventional value of ampere-90	1.00000008887 A
conventional value of coulomb-90	1.00000008887 C
conventional value of farad-90	0.9999999822 F
conventional value of henry-90	1.00000001779 H
conventional value of Josephson constant	483597900000000.0 Hz V^-1
conventional value of ohm-90	1.00000001779 ohm
conventional value of volt-90	1.00000010666 V
conventional value of von Klitzing constant	25812.807 ohm
conventional value of watt-90	1.00000019553 W
Cu x unit	1.00207697e-13 m
deuteron g factor	0.8574382338
deuteron mag. mom.	4.330735094e-27 J T^-1
deuteron mag. mom. to Bohr magneton ratio	0.000466975457
deuteron mag. mom. to nuclear magneton ratio	0.8574382338
deuteron mass	3.3435837724e-27 kg
deuteron mass energy equivalent	3.00506323102e-10 J
deuteron mass energy equivalent in MeV	1875.61294257 MeV
deuteron mass in u	2.013553212745 u
deuteron molar mass	0.00201355321205 kg mol^-1
deuteron relative atomic mass	2.013553212745
deuteron rms charge radius	2.12799e-15 m
deuteron-electron mag. mom. ratio	-0.0004664345551
deuteron-electron mass ratio	3670.48296788
deuteron-neutron mag. mom. ratio	-0.44820653
deuteron-proton mag. mom. ratio	0.30701220939
deuteron-proton mass ratio	1.99900750139
electron charge to mass quotient	-175882001076.0 C kg^-1
electron g factor	-2.00231930436256
electron gyromag. ratio	176085963023.0 s^-1 T^-1
electron gyromag. ratio in MHz/T	28024.9514242 MHz T^-1
electron mag. mom.	-9.2847647043e-24 J T^-1
electron mag. mom. anomaly	0.00115965218128
electron mag. mom. to Bohr magneton ratio	-1.00115965218128
electron mag. mom. to nuclear magneton ratio	-1838.28197188
electron mass	9.1093837015e-31 kg
electron mass energy equivalent	8.1871057769e-14 J
electron mass energy equivalent in MeV	0.51099895 MeV
electron mass in u	0.000548579909065 u
electron molar mass	5.4857990888e-07 kg mol^-1
electron relative atomic mass	0.000548579909065
electron to alpha particle mass ratio	0.0001370933554787
electron to shielded helion mag. mom. ratio	864.058257
electron to shielded proton mag. mom. ratio	-658.2275971
electron volt	1.602176634e-19 J
electron volt-atomic mass unit relationship	1.07354410233e-09 u
electron volt-hartree relationship	0.036749322175655 E_h
electron volt-hertz relationship	241798924200000.0 Hz
electron volt-inverse meter relationship	806554.3937 m^-1
electron volt-joule relationship	1.602176634e-19 J
electron volt-kelvin relationship	11604.51812 K
electron volt-kilogram relationship	1.782661921e-36 kg
electron-deuteron mag. mom. ratio	-2143.9234915
electron-deuteron mass ratio	0.0002724437107462
electron-helion mass ratio	0.0001819543074573
electron-muon mag. mom. ratio	206.7669883
electron-muon mass ratio	0.00483633169
electron-neutron mag. mom. ratio	960.9205
electron-neutron mass ratio	0.00054386734424
electron-proton mag. mom. ratio	-658.21068789
electron-proton mass ratio	0.000544617021487
electron-tau mass ratio	0.000287585
electron-triton mass ratio	0.0001819200062251
elementary charge	1.602176634e-19 C
elementary charge over h-bar	1519267447000000.0 A J^-1
Faraday constant	96485.33212 C mol^-1
Fermi coupling constant	1.1663787e-05 GeV^-2
fine-structure constant	0.0072973525693
first radiation constant	3.741771852e-16 W m^2
first radiation constant for spectral radiance	1.191042972e-16 W m^2 sr^-1
Hartree energy	4.3597447222071e-18 J
Hartree energy in eV	27.211386245988 eV
hartree-atomic mass unit relationship	2.92126232205e-08 u
hartree-electron volt relationship	27.211386245988 eV
hartree-hertz relationship	6579683920502000.0 Hz
hartree-inverse meter relationship	21947463.13632 m^-1
hartree-joule relationship	4.3597447222071e-18 J
hartree-kelvin relationship	315775.02480407 K
hartree-kilogram relationship	4.8508702095432e-35 kg
helion g factor	-4.255250615
helion mag. mom.	-1.074617532e-26 J T^-1
helion mag. mom. to Bohr magneton ratio	-0.001158740958
helion mag. mom. to nuclear magneton ratio	-2.127625307
helion mass	5.0064127796e-27 kg
helion mass energy equivalent	4.4995394125e-10 J
helion mass energy equivalent in MeV	2808.39160743 MeV
helion mass in u	3.014932247175 u
helion molar mass	0.00301493224613 kg mol^-1
helion relative atomic mass	3.014932247175
helion shielding shift	5.996743e-05
helion-electron mass ratio	5495.88528007
helion-proton mass ratio	2.99315267167
hertz-atomic mass unit relationship	4.4398216652e-24 u
hertz-electron volt relationship	4.135667696e-15 eV
hertz-hartree relationship	1.519829846057e-16 E_h
hertz-inverse meter relationship	3.3356409519815204e-09 m^-1
hertz-joule relationship	6.62607015e-34 J
hertz-kelvin relationship	4.799243073e-11 K
hertz-kilogram relationship	7.372497323e-51 kg
hyperfine transition frequency of Cs-133	9192631770.0 Hz
inverse fine-structure constant	137.035999084
inverse meter-atomic mass unit relationship	1.3310250501e-15 u
inverse meter-electron volt relationship	1.239841984e-06 eV
inverse meter-hartree relationship	4.556335252912e-08 E_h
inverse meter-hertz relationship	299792458.0 Hz
inverse meter-joule relationship	1.986445857e-25 J
inverse meter-kelvin relationship	0.01438776877 K
inverse meter-kilogram relationship	2.210219094e-42 kg
inverse of conductance quantum	12906.40372 ohm
Josephson constant	483597848400000.0 Hz V^-1
joule-atomic mass unit relationship	6700535256.5 u
joule-electron volt relationship	6.241509074e+18 eV
joule-hartree relationship	2.2937122783963e+17 E_h
joule-hertz relationship	1.509190179e+33 Hz
joule-inverse meter relationship	5.034116567e+24 m^-1
joule-kelvin relationship	7.242970516e+22 K
joule-kilogram relationship	1.1126500560536185e-17 kg
kelvin-atomic mass unit relationship	9.2510873014e-14 u
kelvin-electron volt relationship	8.617333262e-05 eV
kelvin-hartree relationship	3.1668115634556e-06 E_h
kelvin-hertz relationship	20836619120.0 Hz
kelvin-inverse meter relationship	69.50348004 m^-1
kelvin-joule relationship	1.380649e-23 J
kelvin-kilogram relationship	1.536179187e-40 kg
kilogram-atomic mass unit relationship	6.0221407621e+26 u
kilogram-electron volt relationship	5.609588603e+35 eV
kilogram-hartree relationship	2.0614857887409e+34 E_h
kilogram-hertz relationship	1.356392489e+50 Hz
kilogram-inverse meter relationship	4.524438335e+41 m^-1
kilogram-joule relationship	8.987551787368176e+16 J
kilogram-kelvin relationship	6.50965726e+39 K
lattice parameter of silicon	5.431020511e-10 m
lattice spacing of ideal Si (220)	1.920155716e-10 m
Loschmidt constant (273.15 K, 100 kPa)	2.651645804e+25 m^-3
Loschmidt constant (273.15 K, 101.325 kPa)	2.686780111e+25 m^-3
luminous efficacy	683.0 lm W^-1
mag. flux quantum	2.067833848e-15 Wb
Mo x unit	1.00209952e-13 m
molar gas constant	8.314462618 J mol^-1 K^-1
molar mass constant	0.00099999999965 kg mol^-1
molar mass of carbon-12	0.0119999999958 kg mol^-1
molar Planck constant	3.990312712e-10 J Hz^-1 mol^-1
molar volume of ideal gas (273.15 K, 100 kPa)	0.02271095464 m^3 mol^-1
molar volume of ideal gas (273.15 K, 101.325 kPa)	0.02241396954 m^3 mol^-1
molar volume of silicon	1.205883199e-05 m^3 mol^-1
muon Compton wavelength	1.17344411e-14 m
muon g factor	-2.0023318418
muon mag. mom.	-4.4904483e-26 J T^-1
muon mag. mom. anomaly	0.00116592089
muon mag. mom. to Bohr magneton ratio	-0.00484197047
muon mag. mom. to nuclear magneton ratio	-8.89059703
muon mass	1.883531627e-28 kg
muon mass energy equivalent	1.692833804e-11 J
muon mass energy equivalent in MeV	105.6583755 MeV
muon mass in u	0.1134289259 u
muon molar mass	0.0001134289259 kg mol^-1
muon-electron mass ratio	206.768283
muon-neutron mass ratio	0.112454517
muon-proton mag. mom. ratio	-3.183345142
muon-proton mass ratio	0.1126095264
muon-tau mass ratio	0.0594635
natural unit of action	1.054571817e-34 J s
natural unit of action in eV s	6.582119569e-16 eV s
natural unit of energy	8.1871057769e-14 J
natural unit of energy in MeV	0.51099895 MeV
natural unit of length	3.8615926796e-13 m
natural unit of mass	9.1093837015e-31 kg
natural unit of momentum	2.730924488e-22 kg m s^-1
natural unit of momentum in MeV/c	0.5109989461 MeV/c
natural unit of time	1.28808866819e-21 s
natural unit of velocity	299792458.0 m s^-1
neutron Compton wavelength	1.31959090581e-15 m
neutron g factor	-3.82608545
neutron gyromag. ratio	183247171.0 s^-1 T^-1
neutron gyromag. ratio in MHz/T	29.1646931 MHz T^-1
neutron mag. mom.	-9.6623651e-27 J T^-1
neutron mag. mom. to Bohr magneton ratio	-0.00104187563
neutron mag. mom. to nuclear magneton ratio	-1.91304273
neutron mass	1.67492749804e-27 kg
neutron mass energy equivalent	1.50534976287e-10 J
neutron mass energy equivalent in MeV	939.56542052 MeV
neutron mass in u	1.00866491595 u
neutron molar mass	0.0010086649156 kg mol^-1
neutron relative atomic mass	1.00866491595
neutron to shielded proton mag. mom. ratio	-0.68499694
neutron-electron mag. mom. ratio	0.00104066882
neutron-electron mass ratio	1838.68366173
neutron-muon mass ratio	8.89248406
neutron-proton mag. mom. ratio	-0.68497934
neutron-proton mass difference	2.30557435e-30 kg
neutron-proton mass difference energy equivalent	2.07214689e-13 J
neutron-proton mass difference energy equivalent in MeV	1.29333236 MeV
neutron-proton mass difference in u	0.00138844933 u
neutron-proton mass ratio	1.00137841931
neutron-tau mass ratio	0.528779
Newtonian constant of gravitation	6.6743e-11 m^3 kg^-1 s^-2
Newtonian constant of gravitation over h-bar c	6.70883e-39 (GeV/c^2)^-2
nuclear magneton	5.0507837461e-27 J T^-1
nuclear magneton in eV/T	3.15245125844e-08 eV T^-1
nuclear magneton in inverse meter per tesla	0.0254262341353 m^-1 T^-1
nuclear magneton in K/T	0.00036582677756 K T^-1
nuclear magneton in MHz/T	7.6225932291 MHz T^-1
Planck constant	6.62607015e-34 J Hz^-1
Planck constant in eV/Hz	4.135667696e-15 eV Hz^-1
Planck length	1.616255e-35 m
Planck mass	2.176434e-08 kg
Planck mass energy equivalent in GeV	1.22089e+19 GeV
Planck temperature	1.416784e+32 K
Planck time	5.391247e-44 s
proton charge to mass quotient	95788331.56 C kg^-1
proton Compton wavelength	1.32140985539e-15 m
proton g factor	5.5856946893
proton gyromag. ratio	267522187.44 s^-1 T^-1
proton gyromag. ratio in MHz/T	42.577478518 MHz T^-1
proton mag. mom.	1.41060679736e-26 J T^-1
proton mag. mom. to Bohr magneton ratio	0.0015210322023
proton mag. mom. to nuclear magneton ratio	2.79284734463
proton mag. shielding correction	2.5689e-05
proton mass	1.67262192369e-27 kg
proton mass energy equivalent	1.50327761598e-10 J
proton mass energy equivalent in MeV	938.27208816 MeV
proton mass in u	1.007276466621 u
proton molar mass	0.00100727646627 kg mol^-1
proton relative atomic mass	1.007276466621
proton rms charge radius	8.414e-16 m
proton-electron mass ratio	1836.15267343
proton-muon mass ratio	8.88024337
proton-neutron mag. mom. ratio	-1.45989805
proton-neutron mass ratio	0.99862347812
proton-tau mass ratio	0.528051
quantum of circulation	0.00036369475516 m^2 s^-1
quantum of circulation times 2	0.00072738951032 m^2 s^-1
reduced Compton wavelength	3.8615926796e-13 m
reduced muon Compton wavelength	1.867594306e-15 m
reduced neutron Compton wavelength	2.1001941552e-16 m
reduced Planck constant	1.054571817e-34 J s
reduced Planck constant in eV s	6.582119569e-16 eV s
reduced Planck constant times c in MeV fm	197.3269804 MeV fm
reduced proton Compton wavelength	2.10308910336e-16 m
reduced tau Compton wavelength	1.110538e-16 m
Rydberg constant	10973731.56816 m^-1
Rydberg constant times c in Hz	3289841960250800.0 Hz
Rydberg constant times hc in eV	13.605693122994 eV
Rydberg constant times hc in J	2.1798723611035e-18 J
Sackur-Tetrode constant (1 K, 100 kPa)	-1.15170753706
Sackur-Tetrode constant (1 K, 101.325 kPa)	-1.16487052358
second radiation constant	0.01438776877 m K
shielded helion gyromag. ratio	203789456.9 s^-1 T^-1
shielded helion gyromag. ratio in MHz/T	32.43409942 MHz T^-1
shielded helion mag. mom.	-1.07455309e-26 J T^-1
shielded helion mag. mom. to Bohr magneton ratio	-0.001158671471
shielded helion mag. mom. to nuclear magneton ratio	-2.127497719
shielded helion to proton mag. mom. ratio	-0.7617665618
shielded helion to shielded proton mag. mom. ratio	-0.7617861313
shielded proton gyromag. ratio	267515315.1 s^-1 T^-1
shielded proton gyromag. ratio in MHz/T	42.57638474 MHz T^-1
shielded proton mag. mom.	1.41057056e-26 J T^-1
shielded proton mag. mom. to Bohr magneton ratio	0.001520993128
shielded proton mag. mom. to nuclear magneton ratio	2.792775599
shielding difference of d and p in HD	2.02e-08
shielding difference of t and p in HT	2.414e-08
speed of light in vacuum	299792458.0 m s^-1
standard acceleration of gravity	9.80665 m s^-2
standard atmosphere	101325.0 Pa
standard-state pressure	100000.0 Pa
Stefan-Boltzmann constant	5.670374419e-08 W m^-2 K^-4
tau Compton wavelength	6.97771e-16 m
tau energy equivalent	1776.86 MeV
tau mass	3.16754e-27 kg
tau mass energy equivalent	2.84684e-10 J
tau mass in u	1.90754 u
tau molar mass	0.00190754 kg mol^-1
tau-electron mass ratio	3477.23
tau-muon mass ratio	16.817
tau-neutron mass ratio	1.89115
tau-proton mass ratio	1.89376
Thomson cross section	6.6524587321e-29 m^2
triton g factor	5.957924931
triton mag. mom.	1.5046095202e-26 J T^-1
triton mag. mom. to Bohr magneton ratio	0.0016223936651
triton mag. mom. to nuclear magneton ratio	2.9789624656
triton mass	5.0073567446e-27 kg
triton mass energy equivalent	4.500387806e-10 J
triton mass energy equivalent in MeV	2808.92113298 MeV
triton mass in u	3.01550071621 u
triton molar mass	0.00301550071517 kg mol^-1
triton relative atomic mass	3.01550071621
triton to proton mag. mom. ratio	1.0666399191
triton-electron mass ratio	5496.92153573
triton-proton mass ratio	2.99371703414
unified atomic mass unit	1.6605390666e-27 kg
vacuum electric permittivity	8.8541878128e-12 F m^-1
vacuum mag. permeability	1.25663706212e-06 N A^-2
von Klitzing constant	25812.80745 ohm
W to Z mass ratio	0.88153
weak mixing angle	0.2229
Wien frequency displacement law constant	58789257570.0 Hz K^-1
Wien wavelength displacement law constant	0.002897771955 m K

Units

SI prefixes

yotta	\(10^{24}\)
zetta	\(10^{21}\)
exa	\(10^{18}\)
peta	\(10^{15}\)
tera	\(10^{12}\)
giga	\(10^{9}\)
mega	\(10^{6}\)
kilo	\(10^{3}\)
hecto	\(10^{2}\)
deka	\(10^{1}\)
deci	\(10^{-1}\)
centi	\(10^{-2}\)
milli	\(10^{-3}\)
micro	\(10^{-6}\)
nano	\(10^{-9}\)
pico	\(10^{-12}\)
femto	\(10^{-15}\)
atto	\(10^{-18}\)
zepto	\(10^{-21}\)

Binary prefixes

kibi	\(2^{10}\)
mebi	\(2^{20}\)
gibi	\(2^{30}\)
tebi	\(2^{40}\)
pebi	\(2^{50}\)
exbi	\(2^{60}\)
zebi	\(2^{70}\)
yobi	\(2^{80}\)

Mass

gram	\(10^{-3}\) kg
metric_ton	\(10^{3}\) kg
grain	one grain in kg
lb	one pound (avoirdupous) in kg
pound	one pound (avoirdupous) in kg
blob	one inch version of a slug in kg (added in 1.0.0)
slinch	one inch version of a slug in kg (added in 1.0.0)
slug	one slug in kg (added in 1.0.0)
oz	one ounce in kg
ounce	one ounce in kg
stone	one stone in kg
grain	one grain in kg
long_ton	one long ton in kg
short_ton	one short ton in kg
troy_ounce	one Troy ounce in kg
troy_pound	one Troy pound in kg
carat	one carat in kg
m_u	atomic mass constant (in kg)
u	atomic mass constant (in kg)
atomic_mass	atomic mass constant (in kg)

Angle

degree	degree in radians
arcmin	arc minute in radians
arcminute	arc minute in radians
arcsec	arc second in radians
arcsecond	arc second in radians

Time

minute	one minute in seconds
hour	one hour in seconds
day	one day in seconds
week	one week in seconds
year	one year (365 days) in seconds
Julian_year	one Julian year (365.25 days) in seconds

Length

inch	one inch in meters
foot	one foot in meters
yard	one yard in meters
mile	one mile in meters
mil	one mil in meters
pt	one point in meters
point	one point in meters
survey_foot	one survey foot in meters
survey_mile	one survey mile in meters
nautical_mile	one nautical mile in meters
fermi	one Fermi in meters
angstrom	one Angstrom in meters
micron	one micron in meters
au	one astronomical unit in meters
astronomical_unit	one astronomical unit in meters
light_year	one light year in meters
parsec	one parsec in meters

Pressure

atm	standard atmosphere in pascals
atmosphere	standard atmosphere in pascals
bar	one bar in pascals
torr	one torr (mmHg) in pascals
mmHg	one torr (mmHg) in pascals
psi	one psi in pascals

Area

hectare	one hectare in square meters
acre	one acre in square meters

Volume

liter	one liter in cubic meters
litre	one liter in cubic meters
gallon	one gallon (US) in cubic meters
gallon_US	one gallon (US) in cubic meters
gallon_imp	one gallon (UK) in cubic meters
fluid_ounce	one fluid ounce (US) in cubic meters
fluid_ounce_US	one fluid ounce (US) in cubic meters
fluid_ounce_imp	one fluid ounce (UK) in cubic meters
bbl	one barrel in cubic meters
barrel	one barrel in cubic meters

Speed

kmh	kilometers per hour in meters per second
mph	miles per hour in meters per second
mach	one Mach (approx., at 15 C, 1 atm) in meters per second
speed_of_sound	one Mach (approx., at 15 C, 1 atm) in meters per second
knot	one knot in meters per second

Temperature

zero_Celsius	zero of Celsius scale in Kelvin
degree_Fahrenheit	one Fahrenheit (only differences) in Kelvins

convert_temperature(val, old_scale, new_scale)

Convert from a temperature scale to another one among Celsius, Kelvin, Fahrenheit, and Rankine scales.

Energy

eV	one electron volt in Joules
electron_volt	one electron volt in Joules
calorie	one calorie (thermochemical) in Joules
calorie_th	one calorie (thermochemical) in Joules
calorie_IT	one calorie (International Steam Table calorie, 1956) in Joules
erg	one erg in Joules
Btu	one British thermal unit (International Steam Table) in Joules
Btu_IT	one British thermal unit (International Steam Table) in Joules
Btu_th	one British thermal unit (thermochemical) in Joules
ton_TNT	one ton of TNT in Joules

Power

hp	one horsepower in watts
horsepower	one horsepower in watts

Force

dyn	one dyne in newtons
dyne	one dyne in newtons
lbf	one pound force in newtons
pound_force	one pound force in newtons
kgf	one kilogram force in newtons
kilogram_force	one kilogram force in newtons

Optics

lambda2nu(lambda_)	Convert wavelength to optical frequency
nu2lambda(nu)	Convert optical frequency to wavelength.

References

CODATA2018

CODATA Recommended Values of the Fundamental Physical Constants 2018.

https://physics.nist.gov/cuu/Constants/