Quantity Value Uncertainty Unit
------------------------------------------------------------------------------------------------------------------------
speed of light in vacuum 299 792 458 (exact) m s^-1
magn. constant 12.566 370 614...e-7 (exact) N A^-2
electric constant 8.854 187 817...e-12 (exact) F m^-1
characteristic impedance of vacuum 376.730 313 461... (exact) ohm
Newtonian constant of gravitation 6.6742e-11 0.0010e-11 m^3 kg^-1 s^-2
Newtonian constant of gravitation over h-bar c 6.7087e-39 0.0010e-39 (GeV/c^2)^-2
Planck constant 6.626 0693e-34 0.000 0011e-34 J s
Planck constant in eV s 4.135 667 43e-15 0.000 000 35e-15 eV s
Planck constant over 2 pi times c in MeV fm 197.326 968 0.000 017 MeV fm
Planck constant over 2 pi 1.054 571 68e-34 0.000 000 18e-34 J s
Planck constant over 2 pi in eV s 6.582 119 15e-16 0.000 000 56e-16 eV s
Planck mass 2.176 45e-8 0.000 16e-8 kg
Planck temperature 1.416 79e32 0.000 11e32 K
Planck length 1.616 24e-35 0.000 12e-35 m
Planck time 5.391 21e-44 0.000 40e-44 s
elementary charge 1.602 176 53e-19 0.000 000 14e-19 C
elementary charge over h 2.417 989 40e14 0.000 000 21e14 A J^-1
magn. flux quantum 2.067 833 72e-15 0.000 000 18e-15 Wb
conductance quantum 7.748 091 733e-5 0.000 000 026e-5 S
inverse of conductance quantum 12 906.403 725 0.000 043 ohm
Josephson constant 483 597.879e9 0.041e9 Hz V^-1
von Klitzing constant 25 812.807 449 0.000 086 ohm
Bohr magneton 927.400 949e-26 0.000 080e-26 J T^-1
Bohr magneton in eV/T 5.788 381 804e-5 0.000 000 039e-5 eV T^-1
Bohr magneton in Hz/T 13.996 2458e9 0.000 0012e9 Hz T^-1
Bohr magneton in inverse meters per tesla 46.686 4507 0.000 0040 m^-1 T^-1
Bohr magneton in K/T 0.671 7131 0.000 0012 K T^-1
nuclear magneton 5.050 783 43e-27 0.000 000 43e-27 J T^-1
nuclear magneton in eV/T 3.152 451 259e-8 0.000 000 021e-8 eV T^-1
nuclear magneton in MHz/T 7.622 593 71 0.000 000 65 MHz T^-1
nuclear magneton in inverse meters per tesla 2.542 623 58e-2 0.000 000 22e-2 m^-1 T^-1
nuclear magneton in K/T 3.658 2637e-4 0.000 0064e-4 K T^-1
fine-structure constant 7.297 352 568e-3 0.000 000 024e-3
inverse fine-structure constant 137.035 999 11 0.000 000 46
Rydberg constant 10 973 731.568 525 0.000 073 m^-1
Rydberg constant times c in Hz 3.289 841 960 360e15 0.000 000 000 022e15 Hz
Rydberg constant times hc in J 2.179 872 09e-18 0.000 000 37e-18 J
Rydberg constant times hc in eV 13.605 6923 0.000 0012 eV
Bohr radius 0.529 177 2108e-10 0.000 000 0018e-10 m
Hartree energy 4.359 744 17e-18 0.000 000 75e-18 J
Hartree energy in eV 27.211 3845 0.000 0023 eV
quantum of circulation 3.636 947 550e-4 0.000 000 024e-4 m^2 s^-1
quantum of circulation times 2 7.273 895 101e-4 0.000 000 048e-4 m^2 s^-1
Fermi coupling constant 1.166 39e-5 0.000 01e-5 GeV^-2
weak mixing angle 0.222 15 0.000 76
electron mass 9.109 3826e-31 0.000 0016e-31 kg
electron mass in u 5.485 799 0945e-4 0.000 000 0024e-4 u
electron mass energy equivalent 8.187 1047e-14 0.000 0014e-14 J
electron mass energy equivalent in MeV 0.510 998 918 0.000 000 044 MeV
electron-muon mass ratio 4.836 331 67e-3 0.000 000 13e-3
electron-tau mass ratio 2.875 64e-4 0.000 47e-4
electron-proton mass ratio 5.446 170 2173e-4 0.000 000 0025e-4
electron-neutron mass ratio 5.438 673 4481e-4 0.000 000 0038e-4
electron-deuteron mass ratio 2.724 437 1095e-4 0.000 000 0013e-4
electron to alpha particle mass ratio 1.370 933 555 75e-4 0.000 000 000 61e-4
electron charge to mass quotient -1.758 820 12e11 0.000 000 15e11 C kg^-1
electron molar mass 5.485 799 0945e-7 0.000 000 0024e-7 kg mol^-1
Compton wavelength 2.426 310 238e-12 0.000 000 016e-12 m
Compton wavelength over 2 pi 386.159 2678e-15 0.000 0026e-15 m
classical electron radius 2.817 940 325e-15 0.000 000 028e-15 m
Thomson cross section 0.665 245 873e-28 0.000 000 013e-28 m^2
electron magn. moment -928.476 412e-26 0.000 080e-26 J T^-1
electron magn. moment to Bohr magneton ratio -1.001 159 652 1859 0.000 000 000 0038
electron magn. moment to nuclear magneton ratio -1838.281 971 07 0.000 000 85
electron magn. moment anomaly 1.159 652 1859e-3 0.000 000 0038e-3
electron g factor -2.002 319 304 3718 0.000 000 000 0075
electron-muon magn. moment ratio 206.766 9894 0.000 0054
electron-proton magn. moment ratio -658.210 6862 0.000 0066
electron to shielded proton magn. moment ratio -658.227 5956 0.000 0071
electron-neutron magn. moment ratio 960.920 50 0.000 23
electron-deuteron magn. moment ratio -2143.923 493 0.000 023
electron to shielded helion magn. moment ratio 864.058 255 0.000 010
electron gyromagn. ratio 1.760 859 74e11 0.000 000 15e11 s^-1 T^-1
electron gyromagn. ratio over 2 pi 28 024.9532 0.0024 MHz T^-1
muon mass 1.883 531 40e-28 0.000 000 33e-28 kg
muon mass in u 0.113 428 9264 0.000 000 0030 u
muon mass energy equivalent 1.692 833 60e-11 0.000 000 29e-11 J
muon mass energy equivalent in MeV 105.658 3692 0.000 0094 MeV
muon-electron mass ratio 206.768 2838 0.000 0054
muon-tau mass ratio 5.945 92e-2 0.000 97e-2
muon-proton mass ratio 0.112 609 5269 0.000 000 0029
muon-neutron mass ratio 0.112 454 5175 0.000 000 0029
muon molar mass 0.113 428 9264e-3 0.000 000 0030e-3 kg mol^-1
muon Compton wavelength 11.734 441 05e-15 0.000 000 30e-15 m
muon Compton wavelength over 2 pi 1.867 594 298e-15 0.000 000 047e-15 m
muon magn. moment -4.490 447 99e-26 0.000 000 40e-26 J T^-1
muon magn. moment to Bohr magneton ratio -4.841 970 45e-3 0.000 000 13e-3
muon magn. moment to nuclear magneton ratio -8.890 596 98 0.000 000 23
muon magn. moment anomaly 1.165 919 81e-3 0.000 000 62e-3
muon g factor -2.002 331 8396 0.000 000 0012
muon-proton magn. moment ratio -3.183 345 118 0.000 000 089
tau mass 3.167 77e-27 0.000 52e-27 kg
tau mass in u 1.907 68 0.000 31 u
tau mass energy equivalent 2.847 05e-10 0.000 46e-10 J
tau mass energy equivalent in MeV 1776.99 0.29 MeV
tau-electron mass ratio 3477.48 0.57
tau-muon mass ratio 16.8183 0.0027
tau-proton mass ratio 1.893 90 0.000 31
tau-neutron mass ratio 1.891 29 0.000 31
tau molar mass 1.907 68e-3 0.000 31e-3 kg mol^-1
tau Compton wavelength 0.697 72e-15 0.000 11e-15 m
tau Compton wavelength over 2 pi 0.111 046e-15 0.000 018e-15 m
proton mass 1.672 621 71e-27 0.000 000 29e-27 kg
proton mass in u 1.007 276 466 88 0.000 000 000 13 u
proton mass energy equivalent 1.503 277 43e-10 0.000 000 26e-10 J
proton mass energy equivalent in MeV 938.272 029 0.000 080 MeV
proton-electron mass ratio 1836.152 672 61 0.000 000 85
proton-muon mass ratio 8.880 243 33 0.000 000 23
proton-tau mass ratio 0.528 012 0.000 086
proton-neutron mass ratio 0.998 623 478 72 0.000 000 000 58
proton charge to mass quotient 9.578 833 76e7 0.000 000 82e7 C kg^-1
proton molar mass 1.007 276 466 88e-3 0.000 000 000 13e-3 kg mol^-1
proton Compton wavelength 1.321 409 8555e-15 0.000 000 0088e-15 m
proton Compton wavelength over 2 pi 0.210 308 9104e-15 0.000 000 0014e-15 m
proton magn. moment 1.410 606 71e-26 0.000 000 12e-26 J T^-1
proton magn. moment to Bohr magneton ratio 1.521 032 206e-3 0.000 000 015e-3
proton magn. moment to nuclear magneton ratio 2.792 847 351 0.000 000 028
proton g factor 5.585 694 701 0.000 000 056
proton-neutron magn. moment ratio -1.459 898 05 0.000 000 34
shielded proton magn. moment 1.410 570 47e-26 0.000 000 12e-26 J T^-1
shielded proton magn. moment to Bohr magneton ratio 1.520 993 132e-3 0.000 000 016e-3
shielded proton magn. moment to nuclear magneton ratio 2.792 775 604 0.000 000 030
proton magn. shielding correction 25.689e-6 0.015e-6
proton gyromagn. ratio 2.675 222 05e8 0.000 000 23e8 s^-1 T^-1
proton gyromagn. ratio over 2 pi 42.577 4813 0.000 0037 MHz T^-1
shielded proton gyromagn. ratio 2.675 153 33e8 0.000 000 23e8 s^-1 T^-1
shielded proton gyromagn. ratio over 2 pi 42.576 3875 0.000 0037 MHz T^-1
proton rms charge radius 0.8750e-15 0.0068e-15 m
neutron mass 1.674 927 28e-27 0.000 000 29e-27 kg
neutron mass in u 1.008 664 915 60 0.000 000 000 55 u
neutron mass energy equivalent 1.505 349 57e-10 0.000 000 26e-10 J
neutron mass energy equivalent in MeV 939.565 360 0.000 081 MeV
neutron-electron mass ratio 1838.683 6598 0.000 0013
neutron-muon mass ratio 8.892 484 02 0.000 000 23
neutron-tau mass ratio 0.528 740 0.000 086
neutron-proton mass ratio 1.001 378 418 70 0.000 000 000 58
neutron molar mass 1.008 664 915 60e-3 0.000 000 000 55e-3 kg mol^-1
neutron Compton wavelength 1.319 590 9067e-15 0.000 000 0088e-15 m
neutron Compton wavelength over 2 pi 0.210 019 4157e-15 0.000 000 0014e-15 m
neutron magn. moment -0.966 236 45e-26 0.000 000 24e-26 J T^-1
neutron magn. moment to Bohr magneton ratio -1.041 875 63e-3 0.000 000 25e-3
neutron magn. moment to nuclear magneton ratio -1.913 042 73 0.000 000 45
neutron g factor -3.826 085 46 0.000 000 90
neutron-electron magn. moment ratio 1.040 668 82e-3 0.000 000 25e-3
neutron-proton magn. moment ratio -0.684 979 34 0.000 000 16
neutron to shielded proton magn. moment ratio -0.684 996 94 0.000 000 16
neutron gyromagn. ratio 1.832 471 83e8 0.000 000 46e8 s^-1 T^-1
neutron gyromagn. ratio over 2 pi 29.164 6950 0.000 0073 MHz T^-1
deuteron mass 3.343 583 35e-27 0.000 000 57e-27 kg
deuteron mass in u 2.013 553 212 70 0.000 000 000 35 u
deuteron mass energy equivalent 3.005 062 85e-10 0.000 000 51e-10 J
deuteron mass energy equivalent in MeV 1875.612 82 0.000 16 MeV
deuteron-electron mass ratio 3670.482 9652 0.000 0018
deuteron-proton mass ratio 1.999 007 500 82 0.000 000 000 41
deuteron molar mass 2.013 553 212 70e-3 0.000 000 000 35e-3 kg mol^-1
deuteron magn. moment 0.433 073 482e-26 0.000 000 038e-26 J T^-1
deuteron magn. moment to Bohr magneton ratio 0.466 975 4567e-3 0.000 000 0050e-3
deuteron magn. moment to nuclear magneton ratio 0.857 438 2329 0.000 000 0092
deuteron-electron magn. moment ratio -4.664 345 548e-4 0.000 000 050e-4
deuteron-proton magn. moment ratio 0.307 012 2084 0.000 000 0045
deuteron-neutron magn. moment ratio -0.448 206 52 0.000 000 11
deuteron rms charge radius 2.1394e-15 0.0028e-15 m
helion mass 5.006 412 14e-27 0.000 000 86e-27 kg
helion mass in u 3.014 932 2434 0.000 000 0058 u
helion mass energy equivalent 4.499 538 84e-10 0.000 000 77e-10 J
helion mass energy equivalent in MeV 2808.391 42 0.000 24 MeV
helion-electron mass ratio 5495.885 269 0.000 011
helion-proton mass ratio 2.993 152 6671 0.000 000 0058
helion molar mass 3.014 932 2434e-3 0.000 000 0058e-3 kg mol^-1
shielded helion magn. moment -1.074 553 024e-26 0.000 000 093e-26 J T^-1
shielded helion magn. moment to Bohr magneton ratio -1.158 671 474e-3 0.000 000 014e-3
shielded helion magn. moment to nuclear magneton ratio -2.127 497 723 0.000 000 025
shielded helion to proton magn. moment ratio -0.761 766 562 0.000 000 012
shielded helion to shielded proton magn. moment ratio -0.761 786 1313 0.000 000 0033
shielded helion gyromagn. ratio 2.037 894 70e8 0.000 000 18e8 s^-1 T^-1
shielded helion gyromagn. ratio over 2 pi 32.434 1015 0.000 0028 MHz T^-1
alpha particle mass 6.644 6565e-27 0.000 0011e-27 kg
alpha particle mass in u 4.001 506 179 149 0.000 000 000 056 u
alpha particle mass energy equivalent 5.971 9194e-10 0.000 0010e-10 J
alpha particle mass energy equivalent in MeV 3727.379 17 0.000 32 MeV
alpha particle-electron mass ratio 7294.299 5363 0.000 0032
alpha particle-proton mass ratio 3.972 599 689 07 0.000 000 000 52
alpha particle molar mass 4.001 506 179 149e-3 0.000 000 000 056e-3 kg mol^-1
Avogadro constant 6.022 1415e23 0.000 0010e23 mol^-1
atomic mass constant 1.660 538 86e-27 0.000 000 28e-27 kg
atomic mass constant energy equivalent 1.492 417 90e-10 0.000 000 26e-10 J
atomic mass constant energy equivalent in MeV 931.494 043 0.000 080 MeV
Faraday constant 96 485.3383 0.0083 C mol^-1
Faraday constant for conventional electric current 96 485.336 0.016 C_90 mol^-1
molar Planck constant 3.990 312 716e-10 0.000 000 027e-10 J s mol^-1
molar Planck constant times c 0.119 626 565 72 0.000 000 000 80 J m mol^-1
molar gas constant 8.314 472 0.000 015 J mol^-1 K^-1
Boltzmann constant 1.380 6505e-23 0.000 0024e-23 J K^-1
Boltzmann constant in eV/K 8.617 343e-5 0.000 015e-5 eV K^-1
Boltzmann constant in Hz/K 2.083 6644e10 0.000 0036e10 Hz K^-1
Boltzmann constant in inverse meters per kelvin 69.503 56 0.000 12 m^-1 K^-1
molar volume of ideal gas (273.15 K, 101.325 kPa) 22.413 996e-3 0.000 039e-3 m^3 mol^-1
Loschmidt constant (273.15 K, 101.325 kPa) 2.686 7773e25 0.000 0047e25 m^-3
molar volume of ideal gas (273.15 K, 100 kPa) 22.710 981e-3 0.000 040e-3 m^3 mol^-1
Sackur-Tetrode constant (1 K, 100 kPa) -1.151 7047 0.000 0044
Sackur-Tetrode constant (1 K, 101.325 kPa) -1.164 8677 0.000 0044
Stefan-Boltzmann constant 5.670 400e-8 0.000 040e-8 W m^-2 K^-4
first radiation constant 3.741 771 38e-16 0.000 000 64e-16 W m^2
first radiation constant for spectral radiance 1.191 042 82e-16 0.000 000 20e-16 W m^2 sr^-1
second radiation constant 1.438 7752e-2 0.000 0025e-2 m K
Wien displacement law constant 2.897 7685e-3 0.000 0051e-3 m K
molar mass of carbon-12 12e-3 (exact) kg mol^-1
molar mass constant 1e-3 (exact) kg mol^-1
conventional value of Josephson constant 483 597.9e9 (exact) Hz V^-1
conventional value of von Klitzing constant 25 812.807 (exact) ohm
standard atmosphere 101 325 (exact) Pa
standard acceleration of gravity 9.806 65 (exact) m s^-2
Cu x unit 1.002 077 10e-13 0.000 000 29e-13 m
Mo x unit 1.002 099 66e-13 0.000 000 53e-13 m
Angstrom star 1.000 015 09e-10 0.000 000 90e-10 m
lattice parameter of silicon 543.102 122e-12 0.000 020e-12 m
{220} lattice spacing of silicon 192.015 5965e-12 0.000 0070e-12 m
molar volume of silicon 12.058 8382e-6 0.000 0024e-6 m^3 mol^-1
electron volt 1.602 176 53e-19 0.000 000 14e-19 J
unified atomic mass unit 1.660 538 86e-27 0.000 000 28e-27 kg


** NIST and others.