Fundamental physical constants
Exponent (base 10) of decimal numbers: e n = 10n .
Units are separated by spaces, positive numbers denote powers, all units to the right of the slash are in the denominator (negative powers).

Planck constant h
6.6260755e-34 J s
h / (2 pi) = 1.05457266e-34 J s
Boltzmann constant kB
1.380658e-23 J/K
Elementary charge e
1.60217733e-19 C
Avogadro number NA
6.0221367e23 particles/mol
Speed of light c
2.99792458e8 m/s
Permeability of vacuum mu0
mu0 = 4 pi e-7 T2 m3/J
12.566370614e-7 T2 m3/J
Permittivity of vacuum epsilon0
epsilon0 = 1 / (mu0 c2)
8.854187817e-12 C2/J m
Fine structure constant alpha
1 / 137.0359895
Electron rest mass me
9.1093897e-31 kg
Proton rest mass mp
1.6726231e-27 kg
Neutron rest mass mn
1.6749286e-27 kg
Bohr magneton muB
muB = e h / (4 pi me)
9.2740154e-24 J/T
Nuclear magneton muN
muN = e h / (4 pi mp)
5.0507866e-27 J/T
Free electron g factor ge
2.002319304386
Free electron gyromagnetic ratio gammae
gammae = 2 pi ge muB / h
1.7608592e11 1/s T
gammae / (2 pi) = 28.024944 GHz/T
Electron magnetic moment mue
mue = -(1/2) ge muB
-9.2847701e-24 J/T
Proton gyromagnetic ratio (H2O) gammap
2.67515255e8 1/s T
gammap / (2 pi) = 42.576375 MHz/T
Proton magnetic moment mup
1.41060761e-26 J/T
Proton-electron ratios
mp / me = 1836.152701
mue / mup = 658.2106881
gammae / gammap = 658.2275841 (protons in water)
Charge-to-mass ratio for electron e / me
1.75880e11 C/kg
Atomic mass unit amu
1.66057e-27 kg
Bohr radius a0
5.29177e-11 m
Electron radius re
2.81792e-15 m
Gas constant R
R = NA kB
8.31451 m2 kg/s2 K mol
Molar volume Vmol
22.41383 m3/kmol
Faraday constant F
F = NA e
9.64846e4 C/mol
Proton g factor (Lande factor) gH
5.585
Gravitational constant G
(6.673 +- 0.010)e-11 m3/kg s2 (CODATA)
6.67390 e-11 m3/kg s2 +- 0.0014 % (Jens Gundlach, Univ. of Washington; from: Der Tagesspiegel 2000-05-08)
(6.6873 +- 0.0094)e-11 m3/kg s2 (Schwarz et al., Science 282, 2230 (1998))
Acceleration due to gravity g
9.80665 m/s2
Compton wavelength of the electron lambdac
lambdac = h / (me c)
2.42631e-12 m

Further useful constants
Atomic energy unit Hartree
1 Hartree = e2 / (4 pi epsilon0 a0)
1 Hartree = 2.625501e+06 J/mol (approx. 627.5 kcal/mol)
USEFUL CONVERSION FACTORS
NMR (Nuclear Magnetic Resonance)
Proton Larmor frequency
nup = gammap / (2 pi) B
nup = 42.5764 MHz/T (H₂O)
EPR (Electron Paramagnetic Resonance, ESR)
(Note that the use of brackets [ ] in the following expressions is not in accordance with standards which require the use of a slash, e.g. A/MHz.)
Electron Larmor frequency
nue = gammae / (2 pi) g / ge B
nue [GHz] = 13.9962 g B [T]
g = 0.07144775 nue [GHz] / B [T]
g = 3.04199 nue [GHz] / nup [MHz]
B [T] = 0.0234872 nup [MHz]
Conversion of Units
1 G = 0.1 mT
1 T = 10 kG
1 mT = 10 G
A [MHz] = 2.80249 (g / ge) A [G]
A [MHz] = 28.0249 (g / ge) A [mT]
A [MHz] = 13.9962 g A [mT]
A [MHz] = 2.99792e4 A [1/cm]
A [1/cm] = 0.333564e-4 A [MHz]
A [1/cm] = 4.66863e-4 g A [mT]