Constants (`scipy.constants`)¶

Physical and mathematical constants and units.

Mathematical constants¶

`pi`	Pi
`golden`	Golden ratio

Physical constants¶

`c`	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 $h$
`hbar`	$\hbar = h/(2\pi)$
`G`	Newtonian constant of gravitation
`g`	standard acceleration of gravity
`e`	elementary charge
`R`	molar gas constant
`alpha`	fine-structure constant
`N_A`	Avogadro constant
`k`	Boltzmann constant
`sigma`	Stefan-Boltzmann constant $\sigma$
`Wien`	Wien displacement law constant
`Rydberg`	Rydberg constant
`m_e`	electron mass
`m_p`	proton mass
`m_n`	neutron mass

Constants database¶

In addition to the above variables containing physical constants, scipy.constants also contains a database of additional physical constants.

`value` (key)	value indexed by key
`unit` (key)	unit indexed by key
`precision` (key)	relative precision indexed by key
`find` (sub)	list all keys containing the string sub

scipy.constants.physical_constants¶

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

Available constants:

`alpha particle mass`
`alpha particle mass energy equivalent`
`alpha particle mass energy equivalent in MeV`
`alpha particle mass in u`
`alpha particle molar mass`
`alpha particle-electron mass ratio`
`alpha particle-proton mass ratio`
`Angstrom star`
`atomic mass constant`
`atomic mass constant energy equivalent`
`atomic mass constant energy equivalent in MeV`
`atomic mass unit-electron volt relationship`
`atomic mass unit-hartree relationship`
`atomic mass unit-hertz relationship`
`atomic mass unit-inverse meter relationship`
`atomic mass unit-joule relationship`
`atomic mass unit-kelvin relationship`
`atomic mass unit-kilogram relationship`
`atomic unit of 1st hyperpolarizablity`
`atomic unit of 2nd hyperpolarizablity`
`atomic unit of action`
`atomic unit of charge`
`atomic unit of charge density`
`atomic unit of current`
`atomic unit of electric dipole moment`
`atomic unit of electric field`
`atomic unit of electric field gradient`
`atomic unit of electric polarizablity`
`atomic unit of electric potential`
`atomic unit of electric quadrupole moment`
`atomic unit of energy`
`atomic unit of force`
`atomic unit of length`
`atomic unit of magnetic dipole moment`
`atomic unit of magnetic flux density`
`atomic unit of magnetizability`
`atomic unit of mass`
`atomic unit of momentum`
`atomic unit of permittivity`
`atomic unit of time`
`atomic unit of velocity`
`Avogadro constant`
`Bohr magneton`
`Bohr magneton in eV/T`
`Bohr magneton in Hz/T`
`Bohr magneton in inverse meters per tesla`
`Bohr magneton in K/T`
`Bohr radius`
`Boltzmann constant`
`Boltzmann constant in eV/K`
`Boltzmann constant in Hz/K`
`Boltzmann constant in inverse meters per kelvin`
`characteristic impedance of vacuum`
`classical electron radius`
`Compton wavelength`
`Compton wavelength over 2 pi`
`conductance quantum`
`conventional value of Josephson constant`
`conventional value of von Klitzing constant`
`Cu x unit`
`deuteron magnetic moment`
`deuteron magnetic moment to Bohr magneton ratio`
`deuteron magnetic moment to nuclear magneton ratio`
`deuteron mass`
`deuteron mass energy equivalent`
`deuteron mass energy equivalent in MeV`
`deuteron mass in u`
`deuteron molar mass`
`deuteron rms charge radius`
`deuteron-electron magnetic moment ratio`
`deuteron-electron mass ratio`
`deuteron-neutron magnetic moment ratio`
`deuteron-proton magnetic moment ratio`
`deuteron-proton mass ratio`
`electric constant`
`electron charge to mass quotient`
`electron g factor`
`electron gyromagnetic ratio`
`electron gyromagnetic ratio over 2 pi`
`electron magnetic moment`
`electron magnetic moment anomaly`
`electron magnetic moment to Bohr magneton ratio`
`electron magnetic moment to nuclear magneton ratio`
`electron mass`
`electron mass energy equivalent`
`electron mass energy equivalent in MeV`
`electron mass in u`
`electron molar mass`
`electron to alpha particle mass ratio`
`electron to shielded helion magnetic moment ratio`
`electron to shielded proton magnetic moment ratio`
`electron volt`
`electron volt-atomic mass unit relationship`
`electron volt-hartree relationship`
`electron volt-hertz relationship`
`electron volt-inverse meter relationship`
`electron volt-joule relationship`
`electron volt-kelvin relationship`
`electron volt-kilogram relationship`
`electron-deuteron magnetic moment ratio`
`electron-deuteron mass ratio`
`electron-muon magnetic moment ratio`
`electron-muon mass ratio`
`electron-neutron magnetic moment ratio`
`electron-neutron mass ratio`
`electron-proton magnetic moment ratio`
`electron-proton mass ratio`
`electron-tau mass ratio`
`elementary charge`
`elementary charge over h`
`Faraday constant`
`Faraday constant for conventional electric current`
`Fermi coupling constant`
`fine-structure constant`
`first radiation constant`
`first radiation constant for spectral radiance`
`Hartree energy`
`Hartree energy in eV`
`hartree-atomic mass unit relationship`
`hartree-electron volt relationship`
`hartree-hertz relationship`
`hartree-inverse meter relationship`
`hartree-joule relationship`
`hartree-kelvin relationship`
`hartree-kilogram relationship`
`helion mass`
`helion mass energy equivalent`
`helion mass energy equivalent in MeV`
`helion mass in u`
`helion molar mass`
`helion-electron mass ratio`
`helion-proton mass ratio`
`hertz-atomic mass unit relationship`
`hertz-electron volt relationship`
`hertz-hartree relationship`
`hertz-inverse meter relationship`
`hertz-joule relationship`
`hertz-kelvin relationship`
`hertz-kilogram relationship`
`inverse fine-structure constant`
`inverse meter-atomic mass unit relationship`
`inverse meter-electron volt relationship`
`inverse meter-hartree relationship`
`inverse meter-hertz relationship`
`inverse meter-joule relationship`
`inverse meter-kelvin relationship`
`inverse meter-kilogram relationship`
`inverse of conductance quantum`
`Josephson constant`
`joule-atomic mass unit relationship`
`joule-electron volt relationship`
`joule-hartree relationship`
`joule-hertz relationship`
`joule-inverse meter relationship`
`joule-kelvin relationship`
`joule-kilogram relationship`
`kelvin-atomic mass unit relationship`
`kelvin-electron volt relationship`
`kelvin-hartree relationship`
`kelvin-hertz relationship`
`kelvin-inverse meter relationship`
`kelvin-joule relationship`
`kelvin-kilogram relationship`
`kilogram-atomic mass unit relationship`
`kilogram-electron volt relationship`
`kilogram-hartree relationship`
`kilogram-hertz relationship`
`kilogram-inverse meter relationship`
`kilogram-joule relationship`
`kilogram-kelvin relationship`
`lattice parameter of silicon`
`Loschmidt constant (273.15 K, 101.325 kPa)`
`magnetic constant`
`magnetic flux quantum`
`Mo x unit`
`molar gas constant`
`molar mass constant`
`molar mass of carbon-12`
`molar Planck constant`
`molar Planck constant times c`
`molar volume of ideal gas (273.15 K, 100 kPa)`
`molar volume of ideal gas (273.15 K, 101.325 kPa)`
`molar volume of silicon`
`muon Compton wavelength`
`muon Compton wavelength over 2 pi`
`muon g factor`
`muon magnetic moment`
`muon magnetic moment anomaly`
`muon magnetic moment to Bohr magneton ratio`
`muon magnetic moment to nuclear magneton ratio`
`muon mass`
`muon mass energy equivalent`
`muon mass energy equivalent in MeV`
`muon mass in u`
`muon molar mass`
`muon-electron mass ratio`
`muon-neutron mass ratio`
`muon-proton magnetic moment ratio`
`muon-proton mass ratio`
`muon-tau mass ratio`
`natural unit of action`
`natural unit of action in eV s`
`natural unit of energy`
`natural unit of energy in MeV`
`natural unit of length`
`natural unit of mass`
`natural unit of momentum`
`natural unit of momentum in MeV/c`
`natural unit of time`
`natural unit of velocity`
`neutron Compton wavelength`
`neutron Compton wavelength over 2 pi`
`neutron g factor`
`neutron gyromagnetic ratio`
`neutron gyromagnetic ratio over 2 pi`
`neutron magnetic moment`
`neutron magnetic moment to Bohr magneton ratio`
`neutron magnetic moment to nuclear magneton ratio`
`neutron mass`
`neutron mass energy equivalent`
`neutron mass energy equivalent in MeV`
`neutron mass in u`
`neutron molar mass`
`neutron to shielded proton magnetic moment ratio`
`neutron-electron magnetic moment ratio`
`neutron-electron mass ratio`
`neutron-muon mass ratio`
`neutron-proton magnetic moment ratio`
`neutron-proton mass ratio`
`neutron-tau mass ratio`
`Newtonian constant of gravitation`
`Newtonian constant of gravitation over h-bar c`
`nuclear magneton`
`nuclear magneton in eV/T`
`nuclear magneton in inverse meters per tesla`
`nuclear magneton in K/T`
`nuclear magneton in MHz/T`
`Planck constant`
`Planck constant in eV s`
`Planck constant over 2 pi`
`Planck constant over 2 pi in eV s`
`Planck constant over 2 pi times c in MeV fm`
`Planck length`
`Planck mass`
`Planck temperature`
`Planck time`
`proton charge to mass quotient`
`proton Compton wavelength`
`proton Compton wavelength over 2 pi`
`proton g factor`
`proton gyromagnetic ratio`
`proton gyromagnetic ratio over 2 pi`
`proton magnetic moment`
`proton magnetic moment to Bohr magneton ratio`
`proton magnetic moment to nuclear magneton ratio`
`proton magnetic shielding correction`
`proton mass`
`proton mass energy equivalent`
`proton mass energy equivalent in MeV`
`proton mass in u`
`proton molar mass`
`proton rms charge radius`
`proton-electron mass ratio`
`proton-muon mass ratio`
`proton-neutron magnetic moment ratio`
`proton-neutron mass ratio`
`proton-tau mass ratio`
`quantum of circulation`
`quantum of circulation times 2`
`Rydberg constant`
`Rydberg constant times c in Hz`
`Rydberg constant times hc in eV`
`Rydberg constant times hc in J`
`Sackur-Tetrode constant (1 K, 100 kPa)`
`Sackur-Tetrode constant (1 K, 101.325 kPa)`
`second radiation constant`
`shielded helion gyromagnetic ratio`
`shielded helion gyromagnetic ratio over 2 pi`
`shielded helion magnetic moment`
`shielded helion magnetic moment to Bohr magneton ratio`
`shielded helion magnetic moment to nuclear magneton ratio`
`shielded helion to proton magnetic moment ratio`
`shielded helion to shielded proton magnetic moment ratio`
`shielded proton gyromagnetic ratio`
`shielded proton gyromagnetic ratio over 2 pi`
`shielded proton magnetic moment`
`shielded proton magnetic moment to Bohr magneton ratio`
`shielded proton magnetic moment to nuclear magneton ratio`
`speed of light in vacuum`
`standard acceleration of gravity`
`standard atmosphere`
`Stefan-Boltzmann constant`
`tau Compton wavelength`
`tau Compton wavelength over 2 pi`
`tau mass`
`tau mass energy equivalent`
`tau mass energy equivalent in MeV`
`tau mass in u`
`tau molar mass`
`tau-electron mass ratio`
`tau-muon mass ratio`
`tau-neutron mass ratio`
`tau-proton mass ratio`
`Thomson cross section`
`unified atomic mass unit`
`von Klitzing constant`
`weak mixing angle`
`Wien displacement law constant`
`{220} lattice spacing of silicon`

Unit prefixes¶

SI¶

`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¶

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

Units¶

Weight¶

`gram`	$10^{-3}$ kg
`metric_ton`	$10^{3}$ kg
`grain`	one grain in kg
`lb`	one pound (avoirdupous) in kg
`oz`	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)

Angle¶

`degree`	degree in radians
`arcmin`	arc minute in radians
`arcsec`	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
`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 Ångström in meters
`micron`	one micron in meters
`au`	one astronomical unit in meters
`light_year`	one light year in meters
`parsec`	one parsec in meters

Pressure¶

`atm`	standard atmosphere in pascals
`bar`	one bar in pascals
`torr`	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
`gallon`	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_imp`	one fluid ounce (UK) in cubic meters
`bbl`	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
`knot`	one knot in meters per second

Temperature¶

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

`C2K` (C)	Convert Celcius to Kelvin
`K2C` (K)	Convert Kelvin to Celcius
`F2C` (F)	Convert Fahrenheit to Celcius
`C2F` (C)	Convert Celcius to Fahrenheit
`F2K` (F)	Convert Fahrenheit to Kelvin
`K2F` (K)	Convert Kelvin to Fahrenheit

Energy¶

`eV`	one electron volt in Joules
`calorie`	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_th`	one British thermal unit (thermochemical) in Joules
`ton_TNT`	one ton of TNT in Joules

Power¶

`hp`	one horsepower in watts

Force¶

`dyn`	one dyne in watts
`lbf`	one pound force in watts
`kgf`	one kilogram force in watts

Optics¶

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

Constants (`scipy.constants`)¶

Mathematical constants¶

Physical constants¶

Constants database¶

Unit prefixes¶