2006 Fundamental Physical Constants --- Complete Listing From: http://physics.nist.gov/constants Quantity Value(Uncertainty) Unit --------------------------------------------------------------------------------------------------------- alpha particle mass 6.644 656 20(33) e-27 kg alpha particle mass energy equivalent 5.971 919 17(30) e-10 J alpha particle mass energy equivalent in MeV 3727.379 109(93) MeV alpha particle mass in u 4.001 506 179 127(62) u alpha particle molar mass 4.001 506 179 127(62) e-3 kg mol^{-1} alpha particle-electron mass ratio 7294.299 5365(31) alpha particle-proton mass ratio 3.972 599 689 51(41) Angstrom star 1.000 014 98(90) e-10 m atomic mass constant 1.660 538 782(83) e-27 kg atomic mass constant energy equivalent 1.492 417 830(74) e-10 J atomic mass constant energy equivalent in MeV 931.494 028(23) MeV atomic mass unit-electron volt relationship 931.494 028(23) e6 eV atomic mass unit-hartree relationship 3.423 177 7149(49) e7 E_h atomic mass unit-hertz relationship 2.252 342 7369(32) e23 Hz atomic mass unit-inverse meter relationship 7.513 006 671(11) e14 m^{-1} atomic mass unit-joule relationship 1.492 417 830(74) e-10 J atomic mass unit-kelvin relationship 1.080 9527(19) e13 K atomic mass unit-kilogram relationship 1.660 538 782(83) e-27 kg atomic unit of 1st hyperpolarizability 3.206 361 533(81) e-53 C^3 m^3 J^{-2} atomic unit of 2nd hyperpolarizability 6.235 380 95(31) e-65 C^4 m^4 J^{-3} atomic unit of action 1.054 571 628(53) e-34 J s atomic unit of charge density 1.081 202 300(27) e12 C m^{-3} atomic unit of current 6.623 617 63(17) e-3 A atomic unit of electric dipole moment 8.478 352 81(21) e-30 C m atomic unit of electric field 5.142 206 32(13) e11 V m^{-1} atomic unit of electric field gradient 9.717 361 66(24) e21 V m^{-2} atomic unit of electric polarizability 1.648 777 2536(34) e-41 C^2 m^2 J^{-1} atomic unit of electric potential 27.211 383 86(68) V atomic unit of electric quadrupole moment 4.486 551 07(11) e-40 C m^2 atomic unit of energy 4.359 743 94(22) e-18 J atomic unit of force 8.238 722 06(41) e-8 N atomic unit of length 0.529 177 208 59(36) e-10 m atomic unit of magnetic dipole moment 1.854 801 830(46) e-23 J T^{-1} atomic unit of magnetic flux density 2.350 517 382(59) e5 T atomic unit of magnetizability 7.891 036 433(27) e-29 J T^{-2} atomic unit of mass 9.109 382 15(45) e-31 kg atomic unit of momentum 1.992 851 565(99) e-24 kg m s^{-1} atomic unit of permittivity 1.112 650 056... e-10 F m^{-1} atomic unit of time 2.418 884 326 505(16) e-17 s atomic unit of velocity 2.187 691 2541(15) e6 m s^{-1} Avogadro constant 6.022 141 79(30) e23 mol^{-1} Bohr magneton 927.400 915(23) e-26 J T^{-1} Bohr magneton in Hz/T 13.996 246 04(35) e9 Hz T^{-1} Bohr magneton in K/T 0.671 7131(12) K T^{-1} Bohr magneton in eV/T 5.788 381 7555(79) e-5 eV T^{-1} Bohr magneton in inverse meters per tesla 46.686 4515(12) m^{-1} T^{-1} Bohr radius 0.529 177 208 59(36) e-10 m Boltzmann constant 1.380 6504(24) e-23 J K^{-1} Boltzmann constant in Hz/K 2.083 6644(36) e10 Hz K^{-1} Boltzmann constant in eV/K 8.617 343(15) e-5 eV K^{-1} Boltzmann constant in inverse meters per kelvin 69.503 56(12) m^{-1} K^{-1} characteristic impedance of vacuum 376.730 313 461... Ohm classical electron radius 2.817 940 2894(58) e-15 m Compton wavelength 2.426 310 2175(33) e-12 m Compton wavelength over 2 pi 386.159 264 59(53) e-15 m conductance quantum 7.748 091 7004(53) e-5 S conventional value of Josephson constant 483 597.9 e9 Hz V^{-1} conventional value of von Klitzing constant 25 812.807 Ohm Cu x unit 1.002 076 99(28) e-13 m deuteron g factor 0.857 438 2308(72) deuteron magnetic moment 0.433 073 465(11) e-26 J T^{-1} deuteron magnetic moment to Bohr magneton ratio 0.466 975 4556(39) e-3 deuteron magnetic moment to nuclear magneton ratio 0.857 438 2308(72) deuteron mass 3.343 583 20(17) e-27 kg deuteron mass energy equivalent 3.005 062 72(15) e-10 J deuteron mass energy equivalent in MeV 1875.612 793(47) MeV deuteron mass in u 2.013 553 212 724(78) u deuteron molar mass 2.013 553 212 724(78) e-3 kg mol^{-1} deuteron rms charge radius 2.1402(28) e-15 m deuteron-electron magnetic moment ratio -4.664 345 537(39) e-4 deuteron-electron mass ratio 3670.482 9654(16) deuteron-neutron magnetic moment ratio -0.448 206 52(11) deuteron-proton magnetic moment ratio 0.307 012 2070(24) deuteron-proton mass ratio 1.999 007 501 08(22) electric constant 8.854 187 817... e-12 F m^{-1} electron charge to mass quotient -1.758 820 150(44) e11 C kg^{-1} electron g factor -2.002 319 304 3622(15) electron gyromagnetic ratio 1.760 859 770(44) e11 s^{-1} T^{-1} electron gyromagnetic ratio over 2 pi 28 024.953 64(70) MHz T^{-1} electron magnetic moment -928.476 377(23) e-26 J T^{-1} electron magnetic moment anomaly 1.159 652 181 11(74) e-3 electron magnetic moment to Bohr magneton ratio -1.001 159 652 181 11(74) electron magnetic moment to nuclear magneton ratio -1838.281 970 92(80) electron mass 9.109 382 15(45) e-31 kg electron mass energy equivalent 8.187 104 38(41) e-14 J electron mass energy equivalent in MeV 0.510 998 910(13) MeV electron mass in u 5.485 799 0943(23) e-4 u electron molar mass 5.485 799 0943(23) e-7 kg mol^{-1} electron to alpha particle mass ratio 1.370 933 555 70(58) e-4 electron to shielded helion magnetic moment ratio 864.058 257(10) electron to shielded proton magnetic moment ratio -658.227 5971(72) electron volt 1.602 176 487(40) e-19 J electron volt-atomic mass unit relationship 1.073 544 188(27) e-9 u electron volt-hartree relationship 3.674 932 540(92) e-2 E_h electron volt-hertz relationship 2.417 989 454(60) e14 Hz electron volt-inverse meter relationship 8.065 544 65(20) e5 m^{-1} electron volt-joule relationship 1.602 176 487(40) e-19 J electron volt-kelvin relationship 1.160 4505(20) e4 K electron volt-kilogram relationship 1.782 661 758(44) e-36 kg electron-deuteron magnetic moment ratio -2143.923 498(18) electron-deuteron mass ratio 2.724 437 1093(12) e-4 electron-muon magnetic moment ratio 206.766 9877(52) electron-muon mass ratio 4.836 331 71(12) e-3 electron-neutron magnetic moment ratio 960.920 50(23) electron-neutron mass ratio 5.438 673 4459(33) e-4 electron-proton magnetic moment ratio -658.210 6848(54) electron-proton mass ratio 5.446 170 2177(24) e-4 electron-tau mass ratio 2.875 64(47) e-4 elementary charge over h 2.417 989 454(60) e14 A J^{-1} Faraday constant 96 485.3399(24) C mol^{-1} Faraday constant for conventional electric current 96 485.3401(48) C_{90} mol^{-1} Fermi coupling constant 1.166 37(1) e-5 GeV^{-2} fine-structure constant 7.297 352 5376(50) e-3 first radiation constant 3.741 771 18(19) e-16 W m^{2} first radiation constant for spectral radiance 1.191 042 759(59) e-16 W m^{2} sr^{-1} Hartree energy in eV 27.211 383 86(68) eV hartree 4.359 743 94(22) e-18 J hartree-atomic mass unit relationship 2.921 262 2986(42) e-8 u hartree-electron volt relationship 27.211 383 86(68) eV hartree-hertz relationship 6.579 683 920 722(44) e15 Hz hartree-inverse meter relationship 2.194 746 313 705(15) e7 m^{-1} hartree-joule relationship 4.359 743 94(22) e-18 J hartree-kelvin relationship 3.157 7465(55) e5 K hartree-kilogram relationship 4.850 869 34(24) e-35 kg helion mass 5.006 411 92(25) e-27 kg helion mass energy equivalent 4.499 538 64(22) e-10 J helion mass energy equivalent in MeV 2808.391 383(70) MeV helion mass in u 3.014 932 2473(26) u helion molar mass 3.014 932 2473(26) e-3 kg mol^{-1} helion-electron mass ratio 5495.885 2765(52) helion-proton mass ratio 2.993 152 6713(26) hertz-atomic mass unit relationship 4.439 821 6294(64) e-24 u hertz-electron volt relationship 4.135 667 33(10) e-15 eV hertz-hartree relationship 1.519 829 846 006(10) e-16 E_h hertz-inverse meter relationship 3.335 640 951... e-9 m^{-1} hertz-joule relationship 6.626 068 96(33) e-34 J hertz-kelvin relationship 4.799 2374(84) e-11 K hertz-kilogram relationship 7.372 496 00(37) e-51 kg inverse fine-structure constant 137.035 999 679(94) inverse meter-atomic mass unit relationship 1.331 025 0394(19) e-15 u inverse meter-electron volt relationship 1.239 841 875(31) e-6 eV inverse meter-hartree relationship 4.556 335 252 760(30) e-8 E_h inverse meter-hertz relationship 299 792 458 Hz inverse meter-joule relationship 1.986 445 501(99) e-25 J inverse meter-kelvin relationship 1.438 7752(25) e-2 K inverse meter-kilogram relationship 2.210 218 70(11) e-42 kg inverse of conductance quantum 12 906.403 7787(88) Ohm Josephson constant 483 597.891(12) e9 Hz V^{-1} joule-atomic mass unit relationship 6.700 536 41(33) e9 u joule-electron volt relationship 6.241 509 65(16) e18 eV joule-hartree relationship 2.293 712 69(11) e17 E_h joule-hertz relationship 1.509 190 450(75) e33 Hz joule-inverse meter relationship 5.034 117 47(25) e24 m^{-1} joule-kelvin relationship 7.242 963(13) e22 K joule-kilogram relationship 1.112 650 056... e-17 kg kelvin-atomic mass unit relationship 9.251 098(16) e-14 u kelvin-electron volt relationship 8.617 343(15) e-5 eV kelvin-hartree relationship 3.166 8153(55) e-6 E_h kelvin-hertz relationship 2.083 6644(36) e10 Hz kelvin-inverse meter relationship 69.503 56(12) m^{-1} kelvin-joule relationship 1.380 6504(24) e-23 J kelvin-kilogram relationship 1.536 1807(27) e-40 kg kilogram-atomic mass unit relationship 6.022 141 79(30) e26 u kilogram-electron volt relationship 5.609 589 12(14) e35 eV kilogram-hartree relationship 2.061 486 16(10) e34 E_h kilogram-hertz relationship 1.356 392 733(68) e50 Hz kilogram-inverse meter relationship 4.524 439 15(23) e41 m^{-1} kilogram-joule relationship 8.987 551 787... e16 J kilogram-kelvin relationship 6.509 651(11) e39 K lattice parameter of silicon 543.102 064(14) e-12 m lattice spacing of Si (220) 192.015 5762(50) e-12 m Loschmidt constant (273.15 K, 101.325 kPa) 2.686 7774(47) e25 m^{-3} magnetic constant 12.566 370 614... e-7 N A^{-2} magnetic flux quantum 2.067 833 667(52) e-15 Wb Mo x unit 1.002 099 55(53) e-13 m molar Planck constant 3.990 312 6821(57) e-10 J s mol^{-1} molar Planck constant times c 0.119 626 564 72(17) J m mol^{-1} molar gas constant 8.314 472(15) J mol^{-1} K^{-1} molar mass constant 1 e-3 kg mol^{-1} molar mass of carbon-12 12 e-3 kg mol^{-1} molar volume of ideal gas (273.15 K, 100 kPa) 22.710 981(40) e-3 m^{3} mol^{-1} molar volume of ideal gas (273.15 K, 101.325 kPa) 22.413 996(39) e-3 m^{3} mol^{-1} molar volume of silicon 12.058 8349(11) e-6 m^{3} mol^{-1} muon Compton wavelength 11.734 441 04(30) e-15 m muon Compton wavelength over 2 pi 1.867 594 295(47) e-15 m muon g factor -2.002 331 8414(12) muon magnetic moment -4.490 447 86(16) e-26 J T^{-1} muon magnetic moment anomaly 1.165 920 69(60) e-3 muon magnetic moment to Bohr magneton ratio -4.841 970 49(12) e-3 muon magnetic moment to nuclear magneton ratio -8.890 597 05(23) muon mass 1.883 531 30(11) e-28 kg muon mass energy equivalent 1.692 833 510(95) e-11 J muon mass energy equivalent in MeV 105.658 3668(38) MeV muon mass in u 0.113 428 9256(29) u muon molar mass 0.113 428 9256(29) e-3 kg mol^{-1} muon-electron mass ratio 206.768 2823(52) muon-neutron mass ratio 0.112 454 5167(29) muon-proton magnetic moment ratio -3.183 345 137(85) muon-proton mass ratio 0.112 609 5261(29) muon-tau mass ratio 5.945 92(97) e-2 natural unit of action 1.054 571 628(53) e-34 J s natural unit of action in eV s 6.582 118 99(16) e-16 eV s natural unit of energy 8.187 104 38(41) e-14 J natural unit of energy in MeV 0.510 998 910(13) MeV natural unit of length 386.159 264 59(53) e-15 m natural unit of mass 9.109 382 15(45) e-31 kg natural unit of momentum 2.730 924 06(14) e-22 kg m s^{-1} natural unit of momentum in MeV/c 0.510 998 910(13) MeV/c natural unit of time 1.288 088 6570(18) e-21 s natural unit of velocity 299 792 458 m s^{-1} neutron Compton wavelength 1.319 590 8951(20) e-15 m neutron Compton wavelength over 2 pi 0.210 019 413 82(31) e-15 m neutron g factor -3.826 085 45(90) neutron gyromagnetic ratio 1.832 471 85(43) e8 s^{-1} T^{-1} neutron gyromagnetic ratio over 2 pi 29.164 6954(69) MHz T^{-1} neutron magnetic moment -0.966 236 41(23) e-26 J T^{-1} neutron magnetic moment to Bohr magneton ratio -1.041 875 63(25) e-3 neutron magnetic moment to nuclear magneton ratio -1.913 042 73(45) neutron mass 1.674 927 211(84) e-27 kg neutron mass energy equivalent 1.505 349 505(75) e-10 J neutron mass energy equivalent in MeV 939.565 346(23) MeV neutron mass in u 1.008 664 915 97(43) u neutron molar mass 1.008 664 915 97(43) e-3 kg mol^{-1} neutron to shielded proton magnetic moment ratio -0.684 996 94(16) neutron-electron magnetic moment ratio 1.040 668 82(25) e-3 neutron-electron mass ratio 1838.683 6605(11) neutron-muon mass ratio 8.892 484 09(23) neutron-proton magnetic moment ratio -0.684 979 34(16) neutron-proton mass ratio 1.001 378 419 18(46) neutron-tau mass ratio 0.528 740(86) Newtonian constant of gravitation 6.674 28(67) e-11 m^3 kg^{-1} s^{-2} Newtonian constant of gravitation over h-bar c 6.708 81(67) e-39 (GeV/c^2)^{-2} nuclear magneton 5.050 783 24(13) e-27 J T^{-1} nuclear magneton in K/T 3.658 2637(64) e-4 K T^{-1} nuclear magneton in MHz/T 7.622 593 84(19) MHz T^{-1} nuclear magneton in eV/T 3.152 451 2326(45) e-8 eV T^{-1} nuclear magneton in inverse meters per tesla 2.542 623 616(64) e-2 m^{-1} T^{-1} Planck constant 6.626 068 96(33) e-34 J s Planck constant in eV s 4.135 667 33(10) e-15 eV s Planck constant over 2 pi 1.054 571 628(53) e-34 J s Planck constant over 2 pi in eV s 6.582 118 99(16) e-16 eV s Planck constant over 2 pi times c in MeV fm 197.326 9631(49) MeV fm Planck length 1.616 252(81) e-35 m Planck mass 2.176 44(11) e-8 kg Planck mass energy equivalent in GeV 1.220 892(61) e19 GeV Planck temperature 1.416 785(71) e32 K Planck time 5.391 24(27) e-44 s proton Compton wavelength 1.321 409 8446(19) e-15 m proton Compton wavelength over 2 pi 0.210 308 908 61(30) e-15 m proton charge to mass quotient 9.578 833 92(24) e7 C kg^{-1} proton g factor 5.585 694 713(46) proton gyromagnetic ratio 2.675 222 099(70) e8 s^{-1} T^{-1} proton gyromagnetic ratio over 2 pi 42.577 4821(11) MHz T^{-1} proton magnetic moment 1.410 606 662(37) e-26 J T^{-1} proton magnetic moment to Bohr magneton ratio 1.521 032 209(12) e-3 proton magnetic moment to nuclear magneton ratio 2.792 847 356(23) proton magnetic shielding correction 25.694(14) e-6 proton mass 1.672 621 637(83) e-27 kg proton mass energy equivalent 1.503 277 359(75) e-10 J proton mass energy equivalent in MeV 938.272 013(23) MeV proton mass in u 1.007 276 466 77(10) u proton molar mass 1.007 276 466 77(10) e-3 kg mol^{-1} proton rms charge radius 0.8768(69) e-15 m proton-electron mass ratio 1836.152 672 47(80) proton-muon mass ratio 8.880 243 39(23) proton-neutron magnetic moment ratio -1.459 898 06(34) proton-neutron mass ratio 0.998 623 478 24(46) proton-tau mass ratio 0.528 012(86) quantum of circulation 3.636 947 5199(50) e-4 m^2 s^{-1} quantum of circulation times 2 7.273 895 040(10) e-4 m^2 s^{-1} Rydberg constant 10 973 731.568 527(73) m^{-1} Rydberg constant times c in Hz 3.289 841 960 361(22) e15 Hz Rydberg constant times hc in J 2.179 871 97(11) e-18 J Rydberg constant times hc in eV 13.605 691 93(34) eV Sackur-Tetrode constant (p0 = 100 kPa) -1.151 7047(44) Sackur-Tetrode constant (p0 = 101 325 Pa) -1.164 8677(44) second radiation constant 1.438 7752(25) e-2 m K shielded helion gyromagnetic ratio 2.037 894 730(56) e8 s^{-1} T^{-1} shielded helion gyromagnetic ratio over 2 pi 32.434 101 98(90) MHz T^{-1} shielded helion magnetic moment -1.074 552 982(30) e-26 J T^{-1} shielded helion magnetic moment to Bohr magneton ratio -1.158 671 471(14) e-3 shielded helion magnetic moment to nuclear magneton ratio -2.127 497 718(25) shielded helion to proton magnetic moment ratio -0.761 766 558(11) shielded helion to shielded proton magnetic moment ratio -0.761 786 1313(33) shielded proton gyromagnetic ratio 2.675 153 362(73) e8 s^{-1} T^{-1} shielded proton gyromagnetic ratio over 2 pi 42.576 3881(12) MHz T^{-1} shielded proton magnetic moment 1.410 570 419(38) e-26 J T^{-1} shielded proton magnetic moment to Bohr magneton ratio 1.520 993 128(17) e-3 shielded proton magnetic moment to nuclear magneton ratio 2.792 775 598(30) speed of light in vacuum 299 792 458 m s^{-1} standard acceleration of gravity 9.806 65 m s^{-2} standard atmosphere 101 325 Pa Stefan-Boltzmann constant 5.670 400(40) e-8 W m^{-2} K^{-4} tau Compton wavelength 0.697 72(11) e-15 m tau Compton wavelength over 2 pi 0.111 046(18) e-15 m tau energy equivalent 1776.99(29) MeV tau mass 3.167 77(52) e-27 kg tau mass energy equivalent 2.847 05(46) e-10 J tau mass in u 1.907 68(31) u tau molar mass 1.907 68(31) e-3 kg mol^{-1} tau-electron mass ratio 3477.48(57) tau-muon mass ratio 16.8183(27) tau-neutron mass ratio 1.891 29(31) tau-proton mass ratio 1.893 90(31) Thomson cross section 0.665 245 8558(27) e-28 m^2 triton g factor 5.957 924 896(76) triton magnetic moment 1.504 609 361(42) e-26 J T^{-1} triton magnetic moment to Bohr magneton ratio 1.622 393 657(21) e-3 triton magnetic moment to nuclear magneton ratio 2.978 962 448(38) triton mass 5.007 355 88(25) e-27 kg triton mass energy equivalent 4.500 387 03(22) e-10 J triton mass energy equivalent in MeV 2808.920 906(70) MeV triton mass in u 3.015 500 7134(25) u triton molar mass 3.015 500 7134(25) e-3 kg mol^{-1} triton to proton magnetic moment ratio 1.066 639 908(10) triton-electron magnetic moment ratio -1.620 514 423(21) e-3 triton-electron mass ratio 5496.921 5269(51) triton-neutron magnetic moment ratio -1.557 185 53(37) triton-proton mass ratio 2.993 717 0309(25) unified atomic mass unit 1.660 538 782(83) e-27 kg von Klitzing constant 25 812.807 557(18) Ohm weak mixing angle 0.222 55(56) Wien frequency displacement law constant 5.878 933(10) e10 Hz K^{-1} Wien wavelength displacement law constant 2.897 7685(51) e-3 m K