= 1.256 637 061... x 10-6
Fundamental Physical Constants --- CODATA 2015 Listing
| Quantity | Symbol | Value | Unit |
| alpha particle-electron mass ratio | |
7294.299 5365(31) | |
| alpha particle mass | |
6.644 656 20(33) x 10-27 | kg |
| alpha particle mass energy equivalent | |
5.971 919 17(30) x 10-10 | 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) x 10-3 | kg mol-1 |
| alpha particle-proton mass ratio | |
3.972 599 689 51(41) | |
| Angstrom star | |
1.000 014 98(90) x 10-10 | m |
| atomic mass constant | |
1.660 538 782(83) x 10-27 | kg |
| atomic mass constant energy equivalent | |
1.492 417 830(74) x 10-10 | J |
| atomic mass constant energy equivalent in MeV | |
931.494 028(23) | MeV |
| atomic mass unit-electron volt relationship | |
931.494 028(23) x 106 | eV |
| atomic unit of mass | |
9.109 382 15(45) x 10-31 | kg |
| atomic mass unit-kilogram relationship | |
1.660 538 782(83) x 10-27 | kg |
| atomic unit of action ( Dirac's Constant ) | |
1.054 571 628(53) x 10-34 | J s |
| atomic unit of charge ( elementary charge ) | |
1.602 176 487(40) x 10-19 | C |
| atomic unit of charge density | |
1.081 202 300(27) x 1012 | C m-3 |
| atomic unit of current | |
6.623 617 63(17) x 10-3 | A |
| atomic unit of electric dipole moment | |
8.478 352 81(21) x 10-30 | C m |
| atomic unit of electric field | |
5.142 206 32(13) x 1011 | V m-1 |
| atomic unit of electric field gradient | |
9.717 361 66(24) x 1021 | V m-2 |
| atomic unit of electric polarizablity | |
1.648 777 2536(34) x 10-41 | C2 m2 J-1 |
| atomic unit of electric potential | |
27.211 383 86(68) | V |
| atomic unit of electric quadrupole moment | |
4.486 551 07(11) x 10-40 | C m2 |
| atomic unit of energy | |
4.359 743 94(22) x 10-18 | J |
| atomic unit of force | |
8.238 722 06(41) x 10-8 | N |
| atomic unit of length | |
0.529 177 208 59(36) x 10-10 | m |
| atomic unit of mass | |
9.109 382 15(45) x 10-31 | kg |
| atomic unit of momentum | |
1.992 851 565(99) x 10-24 | kg m s-1 |
| atomic unit of permittivity | |
1.112 650 056... x 10-10 | F m-1 |
| atomic unit of time | |
2.418 884 326 505(16) x 10-17 | s |
| atomic unit of velocity | |
2.187 691 2541(15) x 106 | m s-1 |
| Avogadro constant, number | |
6.022 141 79(30) x 1023 | mol-1 |
| Bohr magneton | |
927.400 915(23) x 10-26 | J T-1 |
| Bohr magneton in eV/T | |
5.788 381 7555(79) x 10-5 | eV T-1 |
| Bohr magneton in Hz/T | |
13.996 246 04(35) x 109 | Hz T-1 |
| Bohr magneton in inverse meters per tesla | |
46.686 4515(12) | m-1 T-1 |
| Bohr magneton in K/T | |
0.671 7131(12) | K T-1 |
| Bohr radius | |
0.529 177 208 59(36) x 10-10 | m |
| Boltzmann | |
1.380 6504(24) x 10-23 | J K-1 |
| Boltzmann constant in eV/K | |
8.617 343(15) x 10-5 | eV K-1 |
| Boltzmann constant in Hz/K | |
2.083 6644(36) x 1010 | Hz 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... | Ω |
| classical electron radius | |
2.817 940 2894(58) x 10-15 | m |
| Coulomb ( force ) constant | |
8.987 551 787 4 x 109 | N m2 C-2 |
| Compton wavelength | |
2.426 310 2175(33) x 10-12 | m |
| Compton wavelength over 2 pi | |
386.159 264 59(53) x 10-15 | m |
| conductance quantum | |
7.748 091 7004(53) x 10-5 | S |
| deuteron-electron magnetic moment ratio | |
-4.664 345 537(39) x 10-4 | |
| deuteron-electron mass ratio | |
3670.482 9654(16) | |
| deuteron g factor | |
0.857 438 2308(72) | |
| deuteron mass | |
3.343 583 20(17) x 10-27 | kg |
| deuteron mass energy equivalent | |
3.005 062 72(15) x 10-10 | 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) x 10-3 | kg mol-1 |
| deuteron-electron magnetic moment ratio | |
-4.664 345 537(39) x 10-4 | |
| 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) | |
| Dirac's Constant | |
1.054 571 628(53) x 10-34 | J s |
| electric constant ( vacuum permittivity ) | |
8.854 187 817... x 10-12 | F m-1 |
| electron charge to mass quotient | |
-1.758 820 150(44) x 1011 | C kg-1 |
| electron-deuteron magnetic moment ratio | |
-2143.923 498(18) | |
| electron-deuteron mass ratio | |
2.724 437 1093(12) x 10-4 | |
| electron g factor | |
-2.002 319 304 3622(15) | |
| electron mass | |
9.109 382 15(45) x 10-31 | kg |
| electron mass energy equivalent | |
8.187 104 38(41) x 10-14 | J |
| electron mass energy equivalent in MeV | |
0.510 998 910(13) | MeV |
| electron mass in u | |
5.485 799 0943(23) x 10-4 | u |
| electron molar mass | |
5.485 799 0943(23) x 10-7 | kg mol-1 |
| electron-muon magnetic moment ratio | |
206.766 9877(52) | |
| electron-muon mass ratio | |
4.836 331 71(12) x 10-3 | |
| electron-neutron magnetic moment ratio | |
960.920 50(23) | |
| electron-neutron mass ratio | |
5.438 673 4459(33) x 10-4 | |
| electron-proton magnetic moment ratio | |
-658.210 6848(54) | |
| electron-proton mass ratio | |
5.446 170 2177(24) x 10-4 | |
| electron-tau mass ratio | |
2.875 64(47) x 10-4 | |
| electron to alpha particle mass ratio | |
1.370 933 555 70(58) x 10-4 | |
| electron volt | |
1.602 176 487(40) x 10-19 | J |
| electron volt-atomic mass unit relationship | |
1.073 544 188(27) x 10-9 | u |
| electron volt-hartree relationship | |
3.674 932 540(92) x 10-2 | Eh |
| electron volt-hertz relationship | |
2.417 989 454(60) x 1014 | Hz |
| electron volt-inverse meter relationship | |
8.065 544 65(20) x 105 | m-1 |
| electron volt-joule relationship | |
1.602 176 487(40) x 10-19 | J |
| electron volt-kelvin relationship | |
1.160 4505(20) x 104 | K |
| electron volt-kilogram relationship | |
1.782 661 758(44) x 10-36 | kg |
| elementary charge | |
1.602 176 487(40) x 10-19 | C |
| elementary charge over h | |
2.417 989 454(60) x 1014 | A J-1 |
| Faraday constant | |
96 485.3399(24) | C mol-1 |
| Faraday constant for conventional electric current | |
96 485.3401(48) | C90 mol-1 |
| Fermi coupling constant | |
1.166 37(1) x 10-5 | GeV-2 |
| fine-structure constant | |
7.297 352 5376(50) x 10-3 | |
| helion-electron mass ratio | |
5495.885 2765(52) | |
| helion mass | |
5.006 411 92(25) x 10-27 | kg |
| helion mass energy equivalent | |
4.499 538 64(22) x 10-10 | 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) x 10-3 | kg mol-1 |
| helion-proton mass ratio | |
2.993 152 6713(26) | |
| hertz-atomic mass unit relationship | |
4.439 821 6294(64) x 10-24 | u |
| hertz-electron volt relationship | |
4.135 667 33(10) x 10-15 | eV |
| hertz-hartree relationship | |
1.519 829 846 006(10) x 10-16 | Eh |
| hertz-inverse meter relationship | |
3.335 640 951ldots x 10-9 | m-1 |
| hertz-joule relationship | |
6.626 068 96(33) x 10-34 | J |
| hertz-kelvin relationship | |
4.799 2374(84) x 10-11 | K |
| hertz-kilogram relationship | |
7.372 496 00(37) x 10-51 | kg |
| inverse fine-structure constant | |
137.035 999 679(94) | |
| inverse meter-atomic mass unit relationship | |
1.331 025 0394(19) x 10-15 | u |
| inverse meter-electron volt relationship | |
1.239 841 875(31) x 10-6 | eV |
| inverse meter-hartree relationship | |
4.556 335 252 760(30) x 10-8 | Eh |
| inverse meter-hertz relationship | |
299 792 458 | Hz |
| inverse meter-joule relationship | |
1.986 445 501(99) x 10-25 | J |
| inverse meter-kelvin relationship | |
1.438 7752(25) x 10-2 | K |
| inverse meter-kilogram relationship | |
2.210 218 70(11) x 10-42 | kg |
| inverse of conductance quantum | |
12 906.403 7787(88) | Ω |
| joule-atomic mass unit relationship | |
6.700 536 41(33) x 109 | u |
| joule-electron volt relationship | |
6.241 509 65(16) x 1018 | eV |
| joule-hartree relationship | |
2.293 712 69(11) x 1017 | Eh |
| joule-hertz relationship | |
1.509 190 450(75) x 1033 | Hz |
| joule-inverse meter relationship | |
5.034 117 47(25) x 1024 | m-1 |
| joule-kelvin relationship | |
7.242 963(13) x 1022 | K |
| joule-kilogram relationship | |
1.112 650 056l ... x 10-17 | kg |
| kelvin-atomic mass unit relationship | |
9.251 098(16) x 10-14 | u |
| kelvin-electron volt relationship | |
8.617 343(15) x 10-5 | eV |
| kelvin-hartree relationship | |
3.166 8153(55) x 10-6 | Eh |
| kelvin-hertz relationship | |
2.083 6644(36) x 1010 | Hz |
| kelvin-inverse meter relationship | |
69.503 56(12) | m-1 |
| kelvin-joule relationship | |
1.380 6504(24) x 10-23 | J |
| kelvin-kilogram relationship | |
1.536 1807(27) x 10-40 | kg |
| kilogram-atomic mass unit relationship | |
6.022 141 79(30) x 1026 | u |
| kilogram-electron volt relationship | |
5.609 589 12(14) x 1035 | eV |
| kilogram-hartree relationship | |
2.061 486 16(10) x 1034 | Eh |
| kilogram-hertz relationship | |
1.356 392 733(68) x 1050 | Hz |
| kilogram-inverse meter relationship | |
4.524 439 15(23) x 1041 | m-1 |
| kilogram-joule relationship | |
8.987 551 787l ... x 1016 | J |
| kilogram-kelvin relationship | |
6.509 651(11) x 1039 | K |
| magnetic constant ( vacuum permeability ) | |
4π x 10-7 = 1.256 637 061... x 10-6 |
N A-2 |
| muon Compton wavelength | |
11.734 441 04(30) x 10-15 | m |
| muon Compton wavelength over 2 pi | |
1.867 594 295(47) x 10-15 | m |
| muon-electron mass ratio | |
206.768 2823(52) | |
| muon-neutron mass ratio | |
0.112 454 5167(29) | |
| muon g factor | |
-2.002 331 8414(12) | |
| muon mass | |
1.883 531 30(11) x 10-28 | kg |
| muon mass energy equivalent | |
1.692 833 510(95) x 10-11 | 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) x 10-3 | kg mol-1 |
| 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) x 10-2 | |
| natural unit of action | |
1.054 571 628(53) x 10-34 | J s |
| natural unit of action in eV s | |
6.582 118 99(16) x 10-16 | eV s |
| natural unit of energy | |
8.187 104 38(41) x 10-14 | J |
| natural unit of energy in MeV | |
0.510 998 910(13) | MeV |
| natural unit of length | |
386.159 264 59(53) x 10-15 | m |
| natural unit of mass | |
9.109 382 15(45) x 10-31 | kg |
| natural unit of momentum | |
2.730 924 06(14) x 10-22 | 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) x 10-21 | s |
| natural unit of velocity | |
299 792 458 | m s-1 |
| neutron Compton wavelength | |
1.319 590 8951(20) x 10-15 | m |
| neutron Compton wavelength over 2 pi | |
0.210 019 413 82(31) x 10-15 | m |
| neutron-electron mass ratio | |
1838.683 6605(11) | |
| neutron g factor | |
-3.826 085 45(90) | |
| neutron mass | |
1.674 927 211(84) x 10-27 | kg |
| neutron mass energy equivalent | |
1.505 349 505(75) x 10-10 | 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) x 10-3 | kg mol-1 |
| neutron-muon mass ratio | |
8.892 484 09(23) | |
| neutron-electron magnetic moment ration | |
1.040 668 82(25) x 10-3 | |
| 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 | |
6.67428(67) x 10-11 | m3 kg-1 s-2 |
| Newtonian constant of gravitation over h-bar c | |
6.708 81(67) x 10-39 | (GeV/c2)-2 |
| nuclear magneton | |
5.050 783 24(13) x 10-27 | J T-1 |
| nuclear magneton in eV/T | |
3.152 451 2326(45) x 10-8 | eV T-1 |
| nuclear magneton in inverse meters per tesla | |
2.542 623 616(64) x 10-2 | m-1 T-1 |
| nuclear magneton in K/T | |
3.658 2637(64) x 10-4 | K T-1 |
| nuclear magneton in MHz/T | |
7.622 593 84(19) | MHz T-1 |
| Planck's constant | |
6.626 068 96(33) x 10-34 | J s |
| Planck's constant in eV s | |
4.135 667 33(10) x 10-15 | eV s |
| Planck's constant over 2 pi ( Dirac's Constant ) | |
1.054 571 628(53) x 10-34 | J s |
| Planck's constant over 2 pi in eV s | |
6.582 118 99(16) x 10-16 | eV s |
| Planck's constant over 2 pi times c in MeV fm | |
197.326 9631(49) | MeV fm |
| Planck length | |
1.616 252(81) x 10-35 | m |
| Planck mass | |
2.176 44(11) x 10-8 | kg |
| Planck mass energy equivalent in GeV | |
1.220 892(61) x 1019 | GeV |
| Planck temperature | |
1.416 785(71) x 1032 | K |
| Planck time | |
5.391 24(27) x 10-44 | s |
| proton charge to mass quotient | |
9.578 833 92(24) x 107 | C kg-1 |
| proton Compton wavelength | |
1.321 409 8446(19) x 10-15 | m |
| proton Compton wavelength over 2 pi | |
0.210 308 908 61(30) x 10-15 | m |
| proton-electron mass ratio | |
1836.152 672 47(80) | |
| proton g factor | |
5.585 694 713(46) | |
| proton mass | |
1.672 621 637(83) x 10-27 | kg |
| proton mass energy equivalent | |
1.503 277 359(75) x 10-10 | 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) x 10-3 | kg mol-1 |
| 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) x 10-4 | m2 s-1 |
| speed of light in vacuo ( vacuum ) | |
299 792 458 | m s-1 |
| standard acceleration of gravity earth's surface at sea level | |
9.806 65 | m s-2 |
| standard atmosphere | |
101 325 | Pa |
| Stefan-Boltzmann constant | |
5.670 400(40) x 10-8 | W m-2 K-4 |
| tau Compton wavelength | |
0.697 72(11) x 10-15 | m |
| tau Compton wavelength over 2 pi | |
0.111 046(18) x 10-15 | m |
| tau-electron mass ratio | |
3477.48(57) | |
| tau mass | |
3.167 77(52) x 10-27 | kg |
| tau mass energy equivalent | |
2.847 05(46) x 10-10 | J |
| tau mass energy equivalent in MeV | |
1776.99(29) | MeV |
| tau mass in u | |
1.907 68(31) | u |
| tau molar mass | |
1.907 68(31) x 10-3 | kg mol-1 |
| tau-muon mass ratio | |
16.8183(27) | |
| tau-neutron mass ratio | |
1.891 29(31) | |
| tau-proton mass ratio | |
1.893 90(31) | |
| triton-electron magnetic moment ratio | |
-1.620 514 423(21) x 10-3 | |
| triton-neutron magnetic moment ratio | |
-1.557 185 53(37) | |
| triton-electron mass ratio | |
5496.921 5269(51) | |
| triton g factor | |
5.957 924 896(76) | |
| triton mass | |
5.007 355 88(25) x 10-27 | kg |
| triton mass energy equivalent | |
4.500 387 03(22) x 10-10 | 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) x 10-3 | kg mol-1 |
| triton-neutron magnetic moment ratio | |
-1.557 185 53(37) | |
| triton-proton magnetic moment ratio | |
1.066 639 908(10) | |
| triton-proton mass ratio | |
2.993 717 0309(25) | |
| unified atomic mass unit | |
1.660 538 782(83) x 10-27 | kg |
Source: http://physics.nist.gov/cuu/Constants/index.html - Latest 2015 CODATA values
note: Values are given in Concise Form: the number in parenthesis is the standard uncertainty, multiplied by the relative standard uncertainty.