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Fundamental Physical Constants
Quantity Value Uncertainty Unit
Speed of light in vacuum299 792 458(exact)m s-1
Magn. constant12.566 370 614...e-7(exact)N A-2
Electric constant8.854 187 817...e-12(exact)F m-1
Characteristic impedance of vacuum376.730 313 461...(exact)ohm
Newtonian constant of gravitation6.6742e-110.0010e-11m3 kg-1 s-2
Newtonian constant of gravitation over h-bar c6.7087e-390.0010e-39(GeV/c2)-2
Planck constant6.626 0693e-340.000 0011e-34J s
Planck constant in eV s4.135 667 43e-150.000 000 35e-15eV s
Planck constant over 2 pi times c in MeV fm197.326 9680.000 017MeV fm
Planck constant over 2 pi1.054 571 68e-340.000 000 18e-34J s
Planck constant over 2 pi in eV s6.582 119 15e-160.000 000 56e-16eV s
Planck mass2.176 45e-80.000 16e-8kg
Planck temperature1.416 79e320.000 11e32K
Planck length1.616 24e-350.000 12e-35m
Planck time5.391 21e-440.000 40e-44s
Elementary charge1.602 176 53e-190.000 000 14e-19C
Elementary charge over h2.417 989 40e140.000 000 21e14A J-1
Magn. flux quantum2.067 833 72e-150.000 000 18e-15Wb
Conductance quantum7.748 091 733e-50.000 000 026e-5S
Inverse of conductance quantum12 906.403 7250.000 043ohm
Josephson constant483 597.879e90.041e9Hz V-1
von Klitzing constant25 812.807 4490.000 086ohm
Bohr magneton927.400 949e-260.000 080e-26J T-1
Bohr magneton in eV/T5.788 381 804e-50.000 000 039e-5eV T-1
Bohr magneton in Hz/T13.996 2458e90.000 0012e9Hz T-1
Bohr magneton in inverse meters per tesla46.686 45070.000 0040m-1 T-1
Bohr magneton in K/T0.671 71310.000 0012K T-1
Nuclear magneton5.050 783 43e-270.000 000 43e-27J T-1
Nuclear magneton in eV/T3.152 451 259e-80.000 000 021e-8eV T-1
Nuclear magneton in MHz/T7.622 593 710.000 000 65MHz T-1
Nuclear magneton in inverse meters per tesla2.542 623 58e-20.000 000 22e-2m-1 T-1
Nuclear magneton in K/T3.658 2637e-40.000 0064e-4K T-1
Fine-structure constant7.297 352 568e-30.000 000 024e-3
Inverse fine-structure constant137.035 999 110.000 000 46
Rydberg constant10 973 731.568 5250.000 073m-1
Rydberg constant times c in Hz3.289 841 960 360e150.000 000 000 022e15Hz
Rydberg constant times hc in J2.179 872 09e-180.000 000 37e-18J
Rydberg constant times hc in eV13.605 69230.000 0012eV
Bohr radius0.529 177 2108e-100.000 000 0018e-10m
Hartree energy4.359 744 17e-180.000 000 75e-18J
Hartree energy in eV27.211 38450.000 0023eV
Quantum of circulation3.636 947 550e-40.000 000 024e-4m2 s-1
Quantum of circulation times 27.273 895 101e-40.000 000 048e-4m2 s-1
Fermi coupling constant1.166 39e-50.000 01e-5GeV-2
Weak mixing angle0.222 150.000 76
Electron mass9.109 3826e-310.000 0016e-31kg
Electron mass in u5.485 799 0945e-40.000 000 0024e-4u
Electron mass energy equivalent8.187 1047e-140.000 0014e-14J
Electron mass energy equivalent in MeV0.510 998 9180.000 000 044MeV
Electron-muon mass ratio4.836 331 67e-30.000 000 13e-3
Electron-tau mass ratio2.875 64e-40.000 47e-4
Electron-proton mass ratio5.446 170 2173e-40.000 000 0025e-4
Electron-neutron mass ratio5.438 673 4481e-40.000 000 0038e-4
Electron-deuteron mass ratio2.724 437 1095e-40.000 000 0013e-4
Electron to alpha particle mass ratio1.370 933 555 75e-40.000 000 000 61e-4
Electron charge to mass quotient-1.758 820 12e110.000 000 15e11C kg-1
Electron molar mass5.485 799 0945e-70.000 000 0024e-7kg mol-1
Compton wavelength2.426 310 238e-120.000 000 016e-12m
Compton wavelength over 2 pi386.159 2678e-150.000 0026e-15m
Classical electron radius2.817 940 325e-150.000 000 028e-15m
Thomson cross section0.665 245 873e-280.000 000 013e-28m2
Electron magn. moment-928.476 412e-260.000 080e-26J T-1
Electron magn. moment to Bohr magneton ratio-1.001 159 652 18590.000 000 000 0038
Electron magn. moment to nuclear magneton ratio-1838.281 971 070.000 000 85
Electron magn. moment anomaly1.159 652 1859e-30.000 000 0038e-3
Electron g factor-2.002 319 304 37180.000 000 000 0075
Electron-muon magn. moment ratio206.766 98940.000 0054
Electron-proton magn. moment ratio-658.210 68620.000 0066
Electron to shielded proton magn. moment ratio-658.227 59560.000 0071
Electron-neutron magn. moment ratio960.920 500.000 23
Electron-deuteron magn. moment ratio-2143.923 4930.000 023
Electron to shielded helion magn. moment ratio864.058 2550.000 010
Electron gyromagn. ratio1.760 859 74e110.000 000 15e11s-1 T-1
Electron gyromagn. ratio over 2 pi28 024.95320.0024MHz T-1
Muon Mass1.883 531 40e-280.000 000 33e-28kg
Muon Mass in u0.113 428 92640.000 000 0030u
Muon Mass energy equivalent1.692 833 60e-110.000 000 29e-11J
Muon Mass energy equivalent in MeV105.658 36920.000 0094MeV
Muon-Electron mass ratio206.768 28380.000 0054
Muon-Tau mass ratio5.945 92e-20.000 97e-2
Muon-Proton mass ratio0.112 609 52690.000 000 0029
Muon-Neutron mass ratio0.112 454 51750.000 000 0029
Muon Molar mass0.113 428 9264e-30.000 000 0030e-3kg mol-1
Muon Compton wavelength11.734 441 05e-150.000 000 30e-15m
Muon Compton wavelength over 2 pi1.867 594 298e-150.000 000 047e-15m
Muon Magn. moment-4.490 447 99e-260.000 000 40e-26J T-1
Muon Magn. moment to Bohr magneton ratio-4.841 970 45e-30.000 000 13e-3
Muon Magn. moment to nuclear magneton ratio-8.890 596 980.000 000 23
Muon Magn. moment anomaly1.165 919 81e-30.000 000 62e-3
Muon G factor-2.002 331 83960.000 000 0012
Muon-Proton magn. moment ratio-3.183 345 1180.000 000 089
Tau Mass3.167 77e-270.000 52e-27kg
Tau Mass in u1.907 680.000 31u
Tau Mass energy equivalent2.847 05e-100.000 46e-10J
Tau Mass energy equivalent in MeV1776.990.29MeV
Tau-Electron mass ratio3477.480.57
Tau-Muon mass ratio16.81830.0027
Tau-Proton mass ratio1.893 900.000 31
Tau-Neutron mass ratio1.891 290.000 31
Tau Molar mass1.907 68e-30.000 31e-3kg mol-1
Tau Compton wavelength0.697 72e-150.000 11e-15m
Tau Compton wavelength over 2 pi0.111 046e-150.000 018e-15m
Proton mass1.672 621 71e-270.000 000 29e-27kg
Proton mass in u1.007 276 466 880.000 000 000 13u
Proton mass energy equivalent1.503 277 43e-100.000 000 26e-10J
Proton mass energy equivalent in MeV938.272 0290.000 080MeV
Proton-electron mass ratio1836.152 672 610.000 000 85
Proton-muon mass ratio8.880 243 330.000 000 23
Proton-tau mass ratio0.528 0120.000 086
Proton-neutron mass ratio0.998 623 478 720.000 000 000 58
Proton charge to mass quotient9.578 833 76e70.000 000 82e7C kg-1
Proton molar mass1.007 276 466 88e-30.000 000 000 13e-3kg mol-1
Proton Compton wavelength1.321 409 8555e-150.000 000 0088e-15m
Proton Compton wavelength over 2 pi0.210 308 9104e-150.000 000 0014e-15m
Proton magn. moment1.410 606 71e-260.000 000 12e-26J T-1
Proton magn. moment to Bohr magneton ratio1.521 032 206e-30.000 000 015e-3
Proton magn. moment to nuclear magneton ratio2.792 847 3510.000 000 028
Proton g factor5.585 694 7010.000 000 056
Proton-neutron magn. moment ratio-1.459 898 050.000 000 34
Shielded proton magn. moment1.410 570 47e-260.000 000 12e-26J T-1
Shielded proton magn. moment to Bohr magneton ratio1.520 993 132e-30.000 000 016e-3
Shielded proton magn. moment to nuclear magneton ratio2.792 775 6040.000 000 030
Proton magn. shielding correction25.689e-60.015e-6
Proton gyromagn. ratio2.675 222 05e80.000 000 23e8s-1 T-1
Proton gyromagn. ratio over 2 pi42.577 48130.000 0037MHz T-1
Shielded proton gyromagn. ratio2.675 153 33e80.000 000 23e8s-1 T-1
Shielded proton gyromagn. ratio over 2 pi42.576 38750.000 0037MHz T-1
Proton rms charge radius0.8750e-150.0068e-15m
Neutron mass1.674 927 28e-270.000 000 29e-27kg
Neutron mass in u1.008 664 915 600.000 000 000 55u
Neutron mass energy equivalent1.505 349 57e-100.000 000 26e-10J
Neutron mass energy equivalent in MeV939.565 3600.000 081MeV
Neutron-electron mass ratio1838.683 65980.000 0013
Neutron-muon mass ratio8.892 484 020.000 000 23
Neutron-tau mass ratio0.528 7400.000 086
Neutron-proton mass ratio1.001 378 418 700.000 000 000 58
Neutron molar mass1.008 664 915 60e-30.000 000 000 55e-3kg mol-1
Neutron Compton wavelength1.319 590 9067e-150.000 000 0088e-15m
Neutron Compton wavelength over 2 pi0.210 019 4157e-150.000 000 0014e-15m
Neutron magn. moment-0.966 236 45e-260.000 000 24e-26J T-1
Neutron magn. moment to Bohr magneton ratio-1.041 875 63e-30.000 000 25e-3
Neutron magn. moment to nuclear magneton ratio-1.913 042 730.000 000 45
Neutron g factor-3.826 085 460.000 000 90
Neutron-electron magn. moment ratio1.040 668 82e-30.000 000 25e-3
Neutron-proton magn. moment ratio-0.684 979 340.000 000 16
Neutron to shielded proton magn. moment ratio-0.684 996 940.000 000 16
Neutron gyromagn. ratio1.832 471 83e80.000 000 46e8s-1 T-1
Neutron gyromagn. ratio over 2 pi29.164 69500.000 0073MHz T-1
Deuteron mass3.343 583 35e-270.000 000 57e-27kg
Deuteron mass in u2.013 553 212 700.000 000 000 35u
Deuteron mass energy equivalent3.005 062 85e-100.000 000 51e-10J
Deuteron mass energy equivalent in MeV1875.612 820.000 16MeV
Deuteron-electron mass ratio3670.482 96520.000 0018
Deuteron-proton mass ratio1.999 007 500 820.000 000 000 41
Deuteron molar mass2.013 553 212 70e-30.000 000 000 35e-3kg mol-1
Deuteron magn. moment0.433 073 482e-260.000 000 038e-26J T-1
Deuteron magn. moment to Bohr magneton ratio0.466 975 4567e-30.000 000 0050e-3
Deuteron magn. moment to nuclear magneton ratio0.857 438 23290.000 000 0092
Deuteron-electron magn. moment ratio-4.664 345 548e-40.000 000 050e-4
Deuteron-proton magn. moment ratio0.307 012 20840.000 000 0045
Deuteron-neutron magn. moment ratio-0.448 206 520.000 000 11
Deuteron rms charge radius2.1394e-150.0028e-15m
Helion mass5.006 412 14e-270.000 000 86e-27kg
Helion mass in u3.014 932 24340.000 000 0058u
Helion mass energy equivalent4.499 538 84e-100.000 000 77e-10J
Helion mass energy equivalent in MeV2808.391 420.000 24MeV
Helion-electron mass ratio5495.885 2690.000 011
Helion-proton mass ratio2.993 152 66710.000 000 0058
Helion molar mass3.014 932 2434e-30.000 000 0058e-3kg mol-1
Shielded helion magn. moment-1.074 553 024e-260.000 000 093e-26J T-1
Shielded helion magn. moment to Bohr magneton ratio-1.158 671 474e-30.000 000 014e-3
Shielded helion magn. moment to nuclear magneton ratio-2.127 497 7230.000 000 025
Shielded helion to proton magn. moment ratio-0.761 766 5620.000 000 012
Shielded helion to shielded proton magn. moment ratio-0.761 786 13130.000 000 0033
Shielded helion gyromagn. ratio2.037 894 70e80.000 000 18e8s-1 T-1
Shielded helion gyromagn. ratio over 2 pi32.434 10150.000 0028MHz T-1
Alpha particle mass6.644 6565e-270.000 0011e-27kg
Alpha particle mass in u4.001 506 179 1490.000 000 000 056u
Alpha particle mass energy equivalent5.971 9194e-100.000 0010e-10J
Alpha particle mass energy equivalent in MeV3727.379 170.000 32MeV
Alpha particle-electron mass ratio7294.299 53630.000 0032
Alpha particle-proton mass ratio3.972 599 689 070.000 000 000 52
Alpha particle molar mass4.001 506 179 149e-30.000 000 000 056e-3kg mol-1
Avogadro constant6.022 1415e230.000 0010e23mol-1
Atomic mass constant1.660 538 86e-270.000 000 28e-27kg
Atomic mass constant energy equivalent1.492 417 90e-100.000 000 26e-10J
Atomic mass constant energy equivalent in MeV931.494 0430.000 080MeV
Faraday constant96 485.33830.0083C mol-1
Faraday constant for conventional electric current96 485.3360.016C_90 mol-1
Molar Planck constant3.990 312 716e-100.000 000 027e-10J s mol-1
Molar Planck constant times c0.119 626 565 720.000 000 000 80J m mol-1
Molar gas constant8.314 4720.000 015J mol-1 K-1
Boltzmann constant1.380 6505e-230.000 0024e-23J K-1
Boltzmann constant in eV/K8.617 343e-50.000 015e-5eV K-1
Boltzmann constant in Hz/K2.083 6644e100.000 0036e10Hz K-1
Boltzmann constant in inverse meters per kelvin69.503 560.000 12m-1 K-1
Molar volume of ideal gas (273.15 K, 101.325 kPa)22.413 996e-30.000 039e-3m3 mol-1
Loschmidt constant (273.15 K, 101.325 kPa)2.686 7773e250.000 0047e25m-3
Molar volume of ideal gas (273.15 K, 100 kPa)22.710 981e-30.000 040e-3m3 mol-1
Sackur-Tetrode constant (1 K, 100 kPa)-1.151 70470.000 0044
Sackur-Tetrode constant (1 K, 101.325 kPa)-1.164 86770.000 0044
Stefan-Boltzmann constant5.670 400e-80.000 040e-8W m-2 K-4
First radiation constant3.741 771 38e-160.000 000 64e-16W m2
First radiation constant for spectral radiance1.191 042 82e-160.000 000 20e-16W m2 sr-1
Second radiation constant1.438 7752e-20.000 0025e-2m K
Wien Displacement law constant2.897 7685e-30.000 0051e-3m K
Molar mass of carbon-1212e-3(exact)kg mol-1
Molar mass constant1e-3(exact)kg mol-1
Conventional value of Josephson constant483 597.9e9(exact)Hz V-1
Conventional value of von Klitzing constant25 812.807(exact)ohm
Standard atmosphere101 325(exact)Pa
Standard acceleration of gravity9.806 65(exact)m s-2
Cu X Unit1.002 077 10e-130.000 000 29e-13m
Mo X Unit1.002 099 66e-130.000 000 53e-13m
Angstrom star1.000 015 09e-100.000 000 90e-10m
Lattice parameter of silicon543.102 122e-120.000 020e-12m
{220} lattice spacing of silicon192.015 5965e-120.000 0070e-12m
Molar volume of silicon12.058 8382e-60.000 0024e-6m3 mol-1
Electron volt1.602 176 53e-190.000 000 14e-19J
Unified atomic mass unit1.660 538 86e-270.000 000 28e-27kg
Natural unit of velocity299 792 458(exact)m s-1
Natural unit of action1.054 571 68e-340.000 000 18e-34J s
Natural unit of action in eV s6.582 119 15e-160.000 000 56e-16eV s
Natural unit of mass9.109 3826e-310.000 0016e-31kg
Natural unit of energy8.187 1047e-140.000 0014e-14J
Natural unit of energy in MeV0.510 998 9180.000 000 044MeV
Natural unit of momentum2.730 924 19e-220.000 000 47e-22kg m s-1
Natural unit of momentum in MeV/c0.510 998 9180.000 000 044MeV/c
Natural unit of length386.159 2678e-150.000 0026e-15m
Natural unit of time1.288 088 6677e-210.000 000 0086e-21s
Atomic unit of charge1.602 176 53e-190.000 000 14e-19C
Atomic unit of mass9.109 3826e-310.000 0016e-31kg
Atomic unit of action1.054 571 68e-340.000 000 18e-34J s
Atomic unit of length0.529 177 2108e-100.000 000 0018e-10m
Atomic unit of energy4.359 744 17e-180.000 000 75e-18J
Atomic unit of time2.418 884 326 505e-170.000 000 000 016e-17s
Atomic unit of force8.238 7225e-80.000 0014e-8N
Atomic unit of velocity2.187 691 2633e60.000 000 0073e6m s-1
Atomic unit of momentum1.992 851 66e-240.000 000 34e-24kg m s-1
Atomic unit of current6.623 617 82e-30.000 000 57e-3A
Atomic unit of charge density1.081 202 317e120.000 000 093e12C m-3
Atomic unit of electric potential27.211 38450.000 0023V
Atomic unit of electric field5.142 206 42e110.000 000 44e11V m-1
Atomic unit of electric field gradient9.717 361 82e210.000 000 83e21V m-2
Atomic unit of electric dipole moment8.478 353 09e-300.000 000 73e-30C m
Atomic unit of electric quadrupole moment4.486 551 24e-400.000 000 39e-40C m2
Atomic unit of electric polarizablity1.648 777 274e-410.000 000 016e-41C2 m2 J-1
Atomic unit of 1st hyperpolarizablity3.206 361 51e-530.000 000 28e-53C3 m3 J-2
Atomic unit of 2nd hyperpolarizablity6.235 3808e-650.000 0011e-65C4 m4 J-3
Atomic unit of magn. flux density2.350 517 42e50.000 000 20e5T
Atomic unit of magn. dipole moment1.854 801 90e-230.000 000 16e-23J T-1
Atomic unit of magnetizability7.891 036 60e-290.000 000 13e-29J T-2
Atomic unit of permittivity1.112 650 056...e-10(exact)F m-1
Joule-kilogram relationship1.112 650 056...e-17(exact)kg
Joule-inverse meter relationship5.034 117 20e240.000 000 86e24m-1
Joule-hertz relationship1.509 190 37e330.000 000 26e33Hz
Joule-kelvin relationship7.242 963e220.000 013e22K
Joule-electron volt relationship6.241 509 47e180.000 000 53e18eV
Joule-atomic mass unit relationship6.700 5361e90.000 0011e9u
Joule-hartree relationship2.293 712 57e170.000 000 39e17E_h
Kilogram-joule relationship8.987 551 787...e16(exact)J
Kilogram-inverse meter relationship4.524 438 91e410.000 000 77e41m-1
Kilogram-hertz relationship1.356 392 66e500.000 000 23e50Hz
Kilogram-kelvin relationship6.509 650e390.000 011e39K
Kilogram-electron volt relationship5.609 588 96e350.000 000 48e35eV
Kilogram-atomic mass unit relationship6.022 1415e260.000 0010e26u
Kilogram-hartree relationship2.061 486 05e340.000 000 35e34E_h
Inverse meter-joule relationship1.986 445 61e-250.000 000 34e-25J
Inverse meter-kilogram relationship2.210 218 81e-420.000 000 38e-42kg
Inverse meter-hertz relationship299 792 458(exact)Hz
Inverse meter-kelvin relationship1.438 7752e-20.000 0025e-2K
Inverse meter-electron volt relationship1.239 841 91e-60.000 000 11e-6eV
Inverse meter-atomic mass unit relationship1.331 025 0506e-150.000 000 0089e-15u
Inverse meter-hartree relationship4.556 335 252 760e-80.000 000 000 030e-8E_h
Hertz-joule relationship6.626 0693e-340.000 0011e-34J
Hertz-kilogram relationship7.372 4964e-510.000 0013e-51kg
Hertz-inverse meter relationship3.335 640 951...e-9(exact)m-1
Hertz-kelvin relationship4.799 2374e-110.000 0084e-11K
Hertz-electron volt relationship4.135 667 43e-150.000 000 35e-15eV
Hertz-atomic mass unit relationship4.439 821 667e-240.000 000 030e-24u
Hertz-hartree relationship1.519 829 846 006e-160.000 000 000 010e-16E_h
Kelvin-joule relationship1.380 6505e-230.000 0024e-23J
Kelvin-kilogram relationship1.536 1808e-400.000 0027e-40kg
Kelvin-inverse meter relationship69.503 560.000 12m-1
Kelvin-hertz relationship2.083 6644e100.000 0036e10Hz
Kelvin-electron volt relationship8.617 343e-50.000 015e-5eV
Kelvin-atomic mass unit relationship9.251 098e-140.000 016e-14u
Kelvin-hartree relationship3.166 8153e-60.000 0055e-6E_h
Electron volt-joule relationship1.602 176 53e-190.000 000 14e-19J
Electron volt-kilogram relationship1.782 661 81e-360.000 000 15e-36kg
Electron volt-inverse meter relationship8.065 544 45e50.000 000 69e5m-1
Electron volt-hertz relationship2.417 989 40e140.000 000 21e14Hz
Electron volt-kelvin relationship1.160 4505e40.000 0020e4K
Electron volt-atomic mass unit relationship1.073 544 171e-90.000 000 092e-9u
Electron volt-hartree relationship3.674 932 45e-20.000 000 31e-2E_h
Atomic mass unit-joule relationship1.492 417 90e-100.000 000 26e-10J
Atomic mass unit-kilogram relationship1.660 538 86e-270.000 000 28e-27kg
Atomic mass unit-inverse meter relationship7.513 006 608e140.000 000 050e14m-1
Atomic mass unit-hertz relationship2.252 342 718e230.000 000 015e23Hz
Atomic mass unit-kelvin relationship1.080 9527e130.000 0019e13K
Atomic mass unit-electron volt relationship931.494 043e60.000 080e6eV
Atomic mass unit-hartree relationship3.423 177 686e70.000 000 023e7E_h
Hartree-joule relationship4.359 744 17e-180.000 000 75e-18J
Hartree-kilogram relationship4.850 869 60e-350.000 000 83e-35kg
Hartree-inverse meter relationship2.194 746 313 705e70.000 000 000 015e7m-1
Hartree-hertz relationship6.579 683 920 721e150.000 000 000 044e15Hz
Hartree-kelvin relationship3.157 7465e50.000 0055e5K
Hartree-electron volt relationship27.211 38450.000 0023eV
Hartree-atomic mass unit relationship2.921 262 323e-80.000 000 019e-8u