1998 Fundamental Physical Constants --- Complete Listing From: http://physics.nist.gov/constants Quantity Value(Uncertainty) Unit --------------------------------------------------------------------------------------------------------- alpha particle mass 6.644 655 98(52) e-27 kg alpha particle mass energy equivalent 5.971 918 97(47) e-10 J alpha particle mass energy equivalent in MeV 3 727.379 04(15) MeV alpha particle mass in u 4.001 506 1747(10) u alpha particle molar mass 4.001 506 1747(10) e-3 kg mol^{-1} alpha particle-electron mass ratio 7 294.299 508(16) alpha particle-proton mass ratio 3.972 599 6846(11) Angstrom star 1.000 015 01(90) e-10 m atomic mass constant 1.660 538 73(13) e-27 kg atomic mass constant energy equivalent 1.492 417 78(12) e-10 J atomic mass constant energy equivalent in MeV 931.494 013(37) MeV atomic mass unit-electron volt relationship 931.494 013(37) e6 eV atomic mass unit-hartree relationship 3.423 177 709(26) e7 E_h atomic mass unit-hertz relationship 2.252 342 733(17) e23 Hz atomic mass unit-inverse meter relationship 7.513 006 658(57) e14 m^{-1} atomic mass unit-joule relationship 1.492 417 78(12) e-10 J atomic mass unit-kelvin relationship 1.080 9528(19) e13 K atomic mass unit-kilogram relationship 1.660 538 73(13) e-27 kg atomic unit of 1st hyperpolarizablity 3.206 361 57(14) e-53 C^3 m^3 J^{-2} atomic unit of 2nd hyperpolarizablity 6.235 381 12(51) e-65 C^4 m^4 J^{-3} atomic unit of action 1.054 571 596(82) e-34 J s atomic unit of charge density 1.081 202 285(43) e12 C m^{-3} atomic unit of current 6.623 617 53(26) e-3 A atomic unit of electric dipole moment 8.478 352 67(33) e-30 C m atomic unit of electric field 5.142 206 24(20) e11 V m^{-1} atomic unit of electric field gradient 9.717 361 53(39) e21 V m^{-2} atomic unit of electric polarizablity 1.648 777 251(18) e-41 C^2 m^2 J^{-1} atomic unit of electric potential 27.211 3834(11) V atomic unit of electric quadrupole moment 4.486 551 00(18) e-40 C m^2 atomic unit of energy 4.359 743 81(34) e-18 J atomic unit of force 8.238 721 81(64) e-8 N atomic unit of length 0.529 177 2083(19) e-10 m atomic unit of magnetic dipole moment 1.854 801 799(75) e-23 J T^{-1} atomic unit of magnetic flux density 2.350 517 349(94) e5 T atomic unit of magnetizability 7.891 036 41(14) e-29 J T^{-2} atomic unit of mass 9.109 381 88(72) e-31 kg atomic unit of momentum 1.992 851 51(16) e-24 kg m s^{-1} atomic unit of permittivity 1.112 650 056... e-10 F m^{-1} atomic unit of time 2.418 884 326 500(18) e-17 s atomic unit of velocity 2.187 691 2529(80) e6 m s^{-1} Avogadro constant 6.022 141 99(47) e23 mol^{-1} Bohr magneton 927.400 899(37) e-26 J T^{-1} Bohr magneton in Hz/T 13.996 246 24(56) e9 Hz T^{-1} Bohr magneton in K/T 0.671 7131(12) K T^{-1} Bohr magneton in eV/T 5.788 381 749(43) e-5 eV T^{-1} Bohr magneton in inverse meters per tesla 46.686 4521(19) m^{-1} T^{-1} Bohr radius 0.529 177 2083(19) e-10 m Boltzmann constant 1.380 6503(24) e-23 J K^{-1} Boltzmann constant in Hz/K 2.083 6644(36) e10 Hz K^{-1} Boltzmann constant in eV/K 8.617 342(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 2.817 940 285(31) e-15 m Compton wavelength 2.426 310 215(18) e-12 m Compton wavelength over 2 pi 386.159 2642(28) e-15 m conductance quantum 7.748 091 696(28) e-5 S conventional value of Josephson constant 483 597 900 000 000.0 GHz V^{-1} conventional value of von Klitzing constant 25 812.807 Ohm Cu x unit 1.002 077 03(28) e-13 m deuteron magnetic moment 0.433 073 457(18) e-26 J T^{-1} deuteron magnetic moment to Bohr magneton ratio 0.466 975 4556(50) e-3 deuteron magnetic moment to nuclear magneton ratio 0.857 438 2284(94) deuteron mass 3.343 583 09(26) e-27 kg deuteron mass energy equivalent 3.005 062 62(24) e-10 J deuteron mass energy equivalent in MeV 1 875.612 762(75) MeV deuteron mass in u 2.013 553 212 71(35) u deuteron molar mass 2.013 553 212 71(35) e-3 kg mol^{-1} deuteron-electron magnetic moment ratio -4.664 345 537(50) e-4 deuteron-electron mass ratio 3 670.482 9550(78) deuteron-neutron magnetic moment ratio -0.448 206 52(11) deuteron-proton magnetic moment ratio 0.307 012 2083(45) deuteron-proton mass ratio 1.999 007 500 83(41) electric constant 8.854 187 817... e-12 F m^{-1} electron charge to mass quotient -1.758 820 174(71) e11 C kg^{-1} electron g factor -2.002 319 304 3737(82) electron gyromagnetic ratio 1.760 859 794(71) e11 s^{-1} T^{-1} electron gyromagnetic ratio over 2 pi 28 024.9540(11) MHz T^{-1} electron magnetic moment -928.476 362(37) e-26 J T^{-1} electron magnetic moment anomaly 1.159 652 1869(41) e-3 electron magnetic moment to Bohr magneton ratio -1.001 159 652 1869(41) electron magnetic moment to nuclear magneton ratio -1 838.281 9660(39) electron mass 9.109 381 88(72) e-31 kg electron mass energy equivalent 8.187 104 14(64) e-14 J electron mass energy equivalent in MeV 0.510 998 902(21) MeV electron mass in u 5.485 799 110(12) e-4 u electron molar mass 5.485 799 110(12) e-7 kg mol^{-1} electron to alpha particle mass ratio 1.370 933 5611(29) e-4 electron to shielded helion magnetic moment ratio 864.058 255(10) electron to shielded proton magnetic moment ratio - 658.227 5954(71) electron volt 1.602 176 462(63) e-19 J electron volt-atomic mass unit relationship 1.073 544 206(43) e-9 u electron volt-hartree relationship 3.674 932 60(14) e-2 E_h electron volt-hertz relationship 2.417 989 491(95) e14 Hz electron volt-inverse meter relationship 8.065 544 77(32) e5 m^{-1} electron volt-joule relationship 1.602 176 462(63) e-19 J electron volt-kelvin relationship 1.160 4506(20) e4 K electron volt-kilogram relationship 1.782 661 731(70) e-36 kg electron-deuteron magnetic moment ratio -2 143.923 498(23) electron-deuteron mass ratio 2.724 437 1170(58) e-4 electron-muon magnetic moment ratio 206.766 9720(63) electron-muon mass ratio 4.836 332 10(15) e-3 electron-neutron magnetic moment ratio 960.920 50(23) electron-neutron mass ratio 5.438 673 462(12) e-4 electron-proton magnetic moment ratio - 658.210 6875(66) electron-proton mass ratio 5.446 170 232(12) e-4 electron-tau mass ratio 2.875 55(47) e-4 elementary charge over h 2.417 989 491(95) e14 A J^{-1} Faraday constant 96 485.3415(39) C mol^{-1} Faraday constant for conventional electric current 96 485.3432(76) C_{90} mol^{-1} Fermi coupling constant 1.166 39(1) e-5 GeV^{-2} fine-structure constant 7.297 352 533(27) e-3 first radiation constant 3.741 771 07(29) e-16 W m^{2} first radiation constant for spectral radiance 1.191 042 722(93) e-16 W m^{2} sr^{-1} Hartree energy in eV 27.211 3834(11) eV hartree 4.359 743 81(34) e-18 J hartree-atomic mass unit relationship 2.921 262 304(22) e-8 u hartree-electron volt relationship 27.211 3834(11) eV hartree-hertz relationship 6.579 683 920 735(50) e15 Hz hartree-inverse meter relationship 2.194 746 313 710(17) e7 m^{-1} hartree-joule relationship 4.359 743 81(34) e-18 J hartree-kelvin relationship 3.157 7465(55) e5 K hartree-kilogram relationship 4.850 869 19(38) e-35 kg helion mass 5.006 411 74(39) e-27 kg helion mass energy equivalent 4.499 538 48(35) e-10 J helion mass energy equivalent in MeV 2 808.391 32(11) MeV helion mass in u 3.014 932 234 69(86) u helion molar mass 3.014 932 234 69(86) e-3 kg mol^{-1} helion-electron mass ratio 5 495.885 238(12) helion-proton mass ratio 2.993 152 658 50(93) hertz-atomic mass unit relationship 4.439 821 637(34) e-24 u hertz-electron volt relationship 4.135 667 27(16) e-15 eV hertz-hartree relationship 1.519 829 846 003(12) e-16 E_h hertz-inverse meter relationship 3.335 640 952 e-9 m^{-1} hertz-joule relationship 6.626 068 76(52) e-34 J hertz-kelvin relationship 4.799 2374(84) e-11 K hertz-kilogram relationship 7.372 495 78(58) e-51 kg inverse fine-structure constant 137.035 999 76(50) inverse meter-atomic mass unit relationship 1.331 025 042(10) e-15 u inverse meter-electron volt relationship 1.239 841 857(49) e-6 eV inverse meter-hartree relationship 4.556 335 252 750(35) e-8 E_h inverse meter-hertz relationship 299 792 458 Hz inverse meter-joule relationship 1.986 445 44(16) e-25 J inverse meter-kelvin relationship 1.438 7752(25) e-2 K inverse meter-kilogram relationship 2.210 218 63(17) e-42 kg inverse of conductance quantum 12 906.403 786(47) Ohm Josephson constant 483 597.898(19) e9 Hz V^{-1} joule-atomic mass unit relationship 6.700 536 62(53) e9 u joule-electron volt relationship 6.241 509 74(24) e18 eV joule-hartree relationship 2.293 712 76(18) e17 E_h joule-hertz relationship 1.509 190 50(12) e33 Hz joule-inverse meter relationship 5.034 117 62(39) e24 m^{-1} joule-kelvin relationship 7.242 964(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 8.617 342(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 6503(24) e-23 J kelvin-kilogram relationship 1.536 1807(27) e-40 kg kilogram-atomic mass unit relationship 6.022 141 99(47) e26 u kilogram-electron volt relationship 5.609 589 21(22) e35 eV kilogram-hartree relationship 2.061 486 22(16) e34 E_h kilogram-hertz relationship 1.356 392 77(11) e50 Hz kilogram-inverse meter relationship 4.524 439 29(35) 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 543.102 088(16) e-12 m lattice spacing of Si (220) 192.015 5845(56) e-12 m Loschmidt constant (273.15 K, 101.325 kPa) 2.686 7775(47) e25 m^{-3} magnetic constant 1 256 637.061 435 917... N A^{-2} magnetic flux quantum 2.067 833 636(81) e-15 Wb Mo x unit 1.002 099 59(53) e-13 m molar Planck constant 3.990 312 689(30) e-10 J s mol^{-1} molar Planck constant times c 0.119 626 564 92(91) 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 8369(14) e-6 m^{3}mol^{-1} muon Compton wavelength 11.734 441 97(35) e-15 m muon Compton wavelength over 2 pi 1.867 594 444(55) e-15 m muon g factor -2.002 331 8320(13) muon magnetic moment -4.490 448 13(22) e-26 J T^{-1} muon magnetic moment anomaly 1.165 916 02(64) e-3 muon magnetic moment to Bohr magneton ratio -4.841 970 85(15) e-3 muon magnetic moment to nuclear magneton ratio -8.890 597 70(27) muon mass 1.883 531 09(16) e-28 kg muon mass energy equivalent 1.692 833 32(14) e-11 J muon mass energy equivalent in MeV 105.658 3568(52) MeV muon mass in u 0.113 428 9168(34) u muon molar mass 0.113 428 9168(34) e-3 kg mol^{-1} muon-electron mass ratio 206.768 2657(63) muon-neutron mass ratio 0.112 454 5079(34) muon-proton magnetic moment ratio -3.183 345 39(10) muon-proton mass ratio 0.112 609 5173(34) muon-tau mass ratio 5.945 72(97) e-2 natural unit of action 1.054 571 596(82) e-34 J s natural unit of action in eV s 6.582 118 89(26) e-16 eV s natural unit of energy 8.187 104 14(64) e-14 J natural unit of energy in MeV 0.510 998 902(21) MeV natural unit of length 386.159 2642(28) e-15 m natural unit of mass 9.109 381 88(72) e-31 kg natural unit of momentum 2.730 923 98(21) e-22 kg m s^{-1} natural unit of momentum in MeV/c 0.510 998 902(21) MeV/c natural unit of time 1.288 088 6555(95) e-21 s natural unit of velocity 299 792 458 m s^{-1} neutron Compton wavelength 1.319 590 898(10) e-15 m neutron Compton wavelength over 2 pi 0.210 019 4142(16) e-15 m neutron g factor -3.826 085 45(90) neutron gyromagnetic ratio 1.832 471 88(44) e8 s^{-1} T^{-1} neutron gyromagnetic ratio over 2 pi 29.164 6958(70) MHz T^{-1} neutron magnetic moment -0.966 236 40(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 72(45) neutron mass 1.674 927 16(13) e-27 kg neutron mass energy equivalent 1.505 349 46(12) e-10 J neutron mass energy equivalent in MeV 939.565 330(38) MeV neutron mass in u 1.008 664 915 78(55) u neutron molar mass 1.008 664 915 78(55) 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 1 838.683 6550(40) neutron-muon mass ratio 8.892 484 78(27) neutron-proton magnetic moment ratio -0.684 979 34(16) neutron-proton mass ratio 1.001 378 418 87(58) neutron-tau mass ratio 0.528 722(86) Newtonian constant of gravitation 6.673(10) e-11 m^3 kg^{-1} s^{-2} Newtonian constant of gravitation over h-bar c 6.707(10) e-39 (GeV/c^2)^{-2} nuclear magneton 5.050 783 17(20) e-27 J T^{-1} nuclear magneton in K/T 3.658 2638(64) e-4 K T^{-1} nuclear magneton in MHz/T 7.622 593 96(31) MHz T^{-1} nuclear magneton in eV/T 3.152 451 238(24) e-8 eV T^{-1} nuclear magneton in inverse meters per tesla 2.542 623 66(10) e-2 m^{-1} T^{-1} Planck constant 6.626 068 76(52) e-34 J s Planck constant in eV s 4.135 667 27(16) e-15 eV s Planck constant over 2 pi 1.054 571 596(82) e-34 J s Planck constant over 2 pi in eV s 6.582 118 89(26) e-16 eV s Planck length 1.6160(12) e-35 m Planck mass 2.1767(16) e-8 kg Planck time 5.3906(40) e-44 s proton Compton wavelength 1.321 409 847(10) e-15 m proton Compton wavelength over 2 pi 0.210 308 9089(16) e-15 m proton charge to mass quotient 9.578 834 08(38) e7 C kg^{-1} proton g factor 5.585 694 675(57) proton gyromagnetic ratio 2.675 222 12(11) e8 s^{-1} T^{-1} proton gyromagnetic ratio over 2 pi 42.577 4825(18) MHz T^{-1} proton magnetic moment 1.410 606 633(58) e-26 J T^{-1} proton magnetic moment to Bohr magneton ratio 1.521 032 203(15) e-3 proton magnetic moment to nuclear magneton ratio 2.792 847 337(29) proton magnetic shielding correction 25.687(15) e-6 proton mass 1.672 621 58(13) e-27 kg proton mass energy equivalent 1.503 277 31(12) e-10 J proton mass energy equivalent in MeV 938.271 998(38) MeV proton mass in u 1.007 276 466 88(13) u proton molar mass 1.007 276 466 88(13) e-3 kg mol^{-1} proton-electron mass ratio 1 836.152 6675(39) proton-muon mass ratio 8.880 244 08(27) proton-neutron magnetic moment ratio -1.459 898 05(34) proton-neutron mass ratio 0.998 623 478 55(58) proton-tau mass ratio 0.527 994(86) quantum of circulation 3.636 947 516(27) e-4 m^2 s^{-1} quantum of circulation times 2 7.273 895 032(53) e-4 m^2 s^{-1} Rydberg constant 10 973 731.568 549(83) m^{-1} Rydberg constant times c in Hz 3.289 841 960 368(25) e15 Hz Rydberg constant times hc in J 2.179 871 90(17) e-18 J Rydberg constant times hc in eV 13.605 691 72(53) eV Sackur-Tetrode constant (p0 = 100 kPa) -1.151 7048(44) Sackur-Tetrode constant (p0 = 101 325 Pa) -1.164 8678(44) second radiation constant 1.438 7752(25) e-2 m K shielded helion gyromagnetic ratio 2.037 894 764(85) e8 s^{-1} T^{-1} shielded helion gyromagnetic ratio over 2 pi 32.434 1025(14) MHz T^{-1} shielded helion magnetic moment -1.074 552 967(45) e-26 J T^{-1} shielded helion magnetic moment to Bohr magneton ratio -1.158 671 474(14) e-3 shielded helion magnetic moment to nuclear magneton ratio -2.127 497 718(25) shielded helion to proton magnetic moment ratio -0.761 766 563(12) shielded helion to shielded proton magnetic moment ratio -0.761 786 1313(33) shielded proton gyromagnetic ratio 2.675 153 41(11) e8 s^{-1} T^{-1} shielded proton gyromagnetic ratio over 2 pi 42.576 3888(18) MHz T^{-1} shielded proton magnetic moment 1.410 570 399(59) e-26 J T^{-1} shielded proton magnetic moment to Bohr magneton ratio 1.520 993 132(16) e-3 shielded proton magnetic moment to nuclear magneton ratio 2.792 775 597(31) 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 70(11) e-15 m tau Compton wavelength over 2 pi 0.111 042(18) e-15 m tau energy equivalent 1 777.05(29) MeV tau mass 3.167 88(52) e-27 kg tau mass energy equivalent 2.847 15(46) e-10 J tau mass in u 1.907 74(31) u tau molar mass 1.907 74(31) e-3 kg mol^{-1} tau-electron mass ratio 3 477.60(57) tau-muon mass ratio 16.8188(27) tau-neutron mass ratio 1.891 35(31) tau-proton mass ratio 1.893 96(31) Thomson cross section 0.665 245 854(15) e-28 m^2 unified atomic mass unit 1.660 538 73(13) e-27 kg von Klitzing constant 25 812.807 572(95) Ohm weak mixing angle 0.2224(19) Wien displacement law constant 2.897 7686(51) e-3 m K