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General Data > Physical Constants

Quantity Value
Speed of light in a vacuum (c) 2.99792458E+08 m/s (exact)
Permeability of a vacuum (µ 0) 4π×1.0E-07 H/m
Permittivity of a vacuum (ε 0) 8.854187817...E-12 F/m
Elementary charge (of proton) 1.60217733(49)E-19 C
Gravitational constant 6.67259(85)E-11 Nm 2kg -2
Unified atomic mass constant (m u = mass 12C / 12) 1.6605402(10)E-27 kg
Rest mass of electron (m e) 9.1093897(54)E-31 kg
5.48579903(13)E-04 amu
Rest mass of proton (m p) 1.6726231(10)E-27 kg
1.007276470(12) amu
1836.152701(37) m e
Rest mass of neutron (m n) 1.6749286(10)E-27 kg
1.008664904(14) amu
Energy equivalence of rest mass of electron 0.5109906(15) MeV
Energy equivalence of rest mass of proton 938.27231(28) MeV
Energy equivalence of rest mass of neutron 939.56563(28) MeV
Electron specific charge (-e/m e) -1.75881962(53)E11 C/kg
Planck constant 6.6260755(40)E-34 Js
h/2π 1.05457266(63)E-34 Js
Rydberg constant 1.0973731534E+07 1/m
Fine structure constant 7.29735308(33)
Reciprocal fine structure constant 137.0359895(61)
Hartree energy 4.3597482(26)E-18 J
2.6255000E+06 J/mol
27.211652 eV
627.51E+03 Calories/mol (US Calorie)
Bohr radius 5.29177249(24)E-11 m
Electron radius 2.81794092(38)E-15 m
Compton wavelength of electron 2.42631058(22)E-12 m
Compton wavelength of proton 1.32141002(12)E-15 m
Compton wavelength of neutron 1.31959110(12)E-15 m
Avogadro constant (N A, L) 6.0221367(36)E+23 1/mol
Faraday constant 9.6485309(29)E+04 C/mol
Molar gas constant 8.314510(70) J/K/mol
Boltzman constant 1.380658(12)E-23 J/K
Stefan-Boltzman constant 5.67051(19)E-08 W/m 2K -4
First radiation constant 3.7417749(22)E-16 Jm 2s -1
Second radiation constant 1.438769(12)E-02 mK
Bohr magneton 9.2740154(31)E-24 J/T
Nuclear magneton 5.0507866(17)E-27 J/T
Magnetic flux quantum 2.06783461(61)E-15 Vs
Gyromagnetic ratio of proton 2.67522128(81)E+08 1/s/T
*1/2π 4.2577469(13)E+07 Hz/T
in pure water 2.67515255(81)E+08 1/s/T
*1/2π 4.2756375(13)E+07 Hz/T
Magnetic moment of electron 9.2847701(31)E-24 J/T
in terms of Bohr magneton 1.001159652(10)
Magnetic moment of proton 1.41060761(47)E-26 J/T
in terms of Bohr magneton 1.521032202(15)E+03
in pure water 1.520993129(17)E+03
in terms of nuclear magneton 2.792847386(63)
Electronvolts per mol 96.485333E+03 J/mol
23.060548E+03 Calories/mol