Structured Lists Directory

Overview

Physical Constants

Physical constants are universal constants that hold true throughout nature, forming the foundation of natural sciences such as physics and chemistry. Recommended values are established by CODATA (Committee on Data for Science and Technology), with representative examples including the speed of light, Planck constant, gravitational constant, and Avogadro constant. Following the 2019 redefinition of SI units, some constants became exact defined values.

physics chemistry constants CODATA NIST SI units natural science
code slug name description symbol uncertainty unit value
c speed-of-light Speed of light in vacuum The propagation speed of light in vacuum. c exact m s^-1 299792458
h planck-constant Planck constant The fundamental constant of quantum mechanics. h exact J Hz^-1 6.62607015e-34
h-bar reduced-planck-constant Reduced Planck constant Planck constant divided by 2π. ℏ exact J s 1.054571817e-34
G gravitational-constant Newtonian constant of gravitation The proportional constant in Newton's law of universal gravitation. G 0.00015e-11 m^3 kg^-1 s^-2 6.67430e-11
Na avogadro-constant Avogadro constant The number of particles in one mole. N_A exact mol^-1 6.02214076e23
e elementary-charge Elementary charge The magnitude of charge carried by an electron. e exact C 1.602176634e-19
k boltzmann-constant Boltzmann constant The conversion factor between temperature and energy. k exact J K^-1 1.380649e-23
alpha fine-structure-constant Fine-structure constant A dimensionless constant representing the strength of electromagnetic interaction. α 0.0000000011e-3 7.2973525643e-3
me electron-mass Electron mass The rest mass of an electron. m_e 0.0000000028e-31 kg 9.1093837139e-31
mp proton-mass Proton mass The rest mass of a proton. m_p 0.00000000052e-27 kg 1.67262192595e-27
mn neutron-mass Neutron mass The rest mass of a neutron. m_n 0.00000000085e-27 kg 1.67492750056e-27
R molar-gas-constant Molar gas constant The constant in the ideal gas law equation. R exact J mol^-1 K^-1 8.314462618
sigma stefan-boltzmann-constant Stefan-Boltzmann constant The constant representing total radiated energy density of blackbody radiation. σ exact W m^-2 K^-4 5.670374419e-8
R-inf rydberg-constant Rydberg constant The constant describing spectral lines of hydrogen atoms. R_∞ 0.000012 m^-1 10973731.568157
a0 bohr-radius Bohr radius The average distance of the electron in the ground state of a hydrogen atom. a_0 0.00000000082e-11 m 5.29177210544e-11
muB bohr-magneton Bohr magneton The natural unit of electron magnetic moment. μ_B 0.0000000029e-24 J T^-1 9.2740100657e-24
muN nuclear-magneton Nuclear magneton The natural unit of nucleon magnetic moment. μ_N 0.0000000016e-27 J T^-1 5.0507837393e-27
F faraday-constant Faraday constant The charge of one mole of electrons. F exact C mol^-1 96485.33212
g standard-acceleration-of-gravity Standard acceleration of gravity The standard acceleration due to gravity at Earth's surface. g exact m s^-2 9.80665

A collection of universal constants that form the foundation of natural science.