| Quantity | Symbol | Value | Error | units | Relative uncertainty (ppm) |
| Universal constants | |||||
| Speed of light in vacuum | c | 299792458 | m s-1 | exact | |
| Permeability of vacuum | m0 | 1.26E-06 | N A-2 | exact | |
| Permittivity of vacuum | e0 | 8.85E-12 | F m-1 | exact | |
| Newtonian constant of gravitation | G | 6.67259E-11 | 8.5E-15 | m3 kg-1 s-2 | 128 |
| Planck constant | h | 6.6260755E-34 | 400.0E-42 | J s | 0.60 |
| Planck constant in eV | h | 4.1356692E-15 | 1.2E-21 | eV s | 0.30 |
| Planck constant over 2p | hbar | 1.05457266E-34 | 63.0E-42 | J s | 0.60 |
| Planck constant over 2p in eV | hbar | 6.5821220E-16 | 200.0E-24 | eV s | 0.30 |
| Planck mass ((hbar c)/G)0.5 | mP | 2.17671E-08 | 1.4E-12 | kg | 64 |
| Planck length (hbar / (mP c)) | lP | 1.61605E-35 | 1.0E-39 | m | 64 |
| Planck time (lP / c) | tP | 5.39056E-44 | 3.4E-48 | s | 64 |
| Electromagnetic constants | |||||
| Elementary charge | e | 1.60217733E-19 | 49.0E-27 | C | 0.30 |
| Elementary charge | e/h | 2.41798836E+14 | 72.0E+6 | A J-1 | 0.30 |
| Magnetic flux quantum | F0 | 2.06783461E-15 | 610.0E-24 | Wb | 0.30 |
| Josephson frequency-voltage quotient | 2e/h | 4.8359767E+14 | 140.0E+6 | Hz V-1 | 0.30 |
| Quantized Hall conductance | e2/h | 3.87404614E-05 | 1.7E-12 | S | 0.045 |
| Quantized Hall resistance | RH | 25812.8056 | 0.0012 | W | 0.045 |
| Bohr magneton (e hbar) / (2 me) | mB | 9.2740154E-24 | 3.1E-30 | J T-1 | 0.34 |
| Bohr magneton in eV | 5.78838263E-05 | 5.2E-12 | eV T-1 | 0.089 | |
| Bohr magneton in hertz | 1.39962418E+10 | 4.2E+3 | Hz T-1 | 0.30 | |
| Bohr magneton in wavenumbers | 46.686437 | 0.000014 | m-1 T-1 | 0.30 | |
| Bohr magneton in kelvins | 6.7170990E-01 | 5.7E-6 | K T-1 | 8.5 | |
| Nuclear magneton (e hbar) / (2 mp) | mN | 5.0507866E-27 | 1.7E-33 | J T-1 | 0.34 |
| Nuclear magneton in eV | 3.15245166E-08 | 2.8E-15 | eV T-1 | 0.089 | |
| Nuclear magneton in hertz | 7.6225914E+00 | 2.3E-6 | MHz T-1 | 0.30 | |
| Nuclear magneton in wavenumbers | 2.54262281E-02 | 7.7E-9 | m-1 T-1 | 0.30 | |
| Nuclear magneton in kelvins | 3.658246E-04 | 3.1E-9 | K T-1 | 8.5 | |
| Atomic constants | |||||
| Fine-structure constant, m0ce2/2h | a | 7.29735308E-03 | 330.0E-12 | 0.045 | |
| inverse fine-structure constant | a-1 | 137.0359895 | 0.0000061 | 0.045 | |
| Rydberg constant (meca2/2h) | Rinf | 10973731.534 | 0.013 | m-1 | 0.0012 |
| Rydberg constant in hertz | 3.2898419499E+15 | 3.9E+6 | Hz | 0.0012 | |
| Rydberg constant in joules | 2.1798741E-18 | 1.3E-24 | J | 0.60 | |
| Rydberg constant in eV | 13.6056981 | 0.0000040 | eV | 0.30 | |
| Bohr radius (a/4pRinf) | a0 | 5.29177249E-11 | 2.4E-18 | m | 0.045 |
| Hartree energy (e2/4pe0a0) | Eh | 4.3597482E-18 | 2.6E-24 | J | 0.60 |
| Hartree energy in eV | 27.2113961 | 0.0000081 | eV | 0.30 | |
| Quantum of circulation | h/2me | 3.63694807E-04 | 33.0E-12 | m2 s-1 | 0.089 |
| h/me | 7.27389614E-04 | 65.0E-12 | m2 s-1 | 0.089 | |
| Electron | |||||
| Mass | me | 9.1093897E-31 | 540.0E-39 | kg | 0.59 |
| Mass in atomic mass units | 5.48579903E-04 | 13.0E-12 | u | 0.023 | |
| Mass in eV | 5.10999060E-01 | 150.0E-9 | eV | 0.30 | |
| Electron-muon mass ratio | me/mm | 4.83633218E-03 | 710.0E-12 | 0.15 | |
| Electron-proton mass ratio | me/mp | 5.44617013E-04 | 11.0E-12 | 0.020 | |
| Electron-deuteron mass ratio | me/md | 2.72443707E-04 | 6.0E-12 | 0.020 | |
| Electron-a-particle mass ratio | me/ma | 1.37093354E-04 | 3.0E-12 | 0.021 | |
| Specific charge | e/me | 1.75881962E+11 | 53.0E+3 | C kg-1 | 0.30 |
| Molar mass | M(e) | 5.48579903E-07 | 13.0E-15 | kg mol-1 | 0.023 |
| Compton wavelength (h/mec) | lC | -2.42631058E-12 | 220.0E-21 | m | 0.089 |
| Compton wavelength /2p | lC/2p | 3.86159323E-13 | 35.0E-21 | m | 0.089 |
| Classical radius, a2a0 | re | 2.81794092E-15 | 380.0E-24 | m | 0.13 |
| Thomson cross section (8p/3)re2 | se | 6.65246160E-29 | 18.0E-36 | m2 | 0.27 |
| Magnetic moment | me | 9.2847701E-24 | 3.1E-30 | J T-1 | 0.34 |
| Magnetic moment in Bohr magnetons | me/mB | 1.001159652193 | 0.000000000010 | 1E-05 | |
| Magnetic moment in Nuclear magnetons | me/mN | 1838.282000 | 0.000037 | 0.020 | |
| Magnetic moment anomaly (me/mB - 1) | ae | 1.159652193E-03 | 10.0E-12 | 0.0086 | |
| g-factor (2 (1 + ae)) | ge | 2.002319304386 | 0.000000000020 | 1E-05 | |
| Electron-muon magnetic moment ratio | me/mm | 206.766967 | 0.000030 | 0.15 | |
| Electron-proton magnetic moment ratio | me/mp | 658.210688 | 0.000007 | 0.010 | |
| Muon | |||||
| Mass | mm | 1.8835327E-28 | 110.0E-36 | kg | 0.61 |
| Mass in atomic mass units | 0.113428913 | 0.000000017 | u | 0.15 | |
| Mass in eV | 105.658389 | 0.000034 | MeV | 0.32 | |
| Muon-electron mass ratio | mm/me | 206.768262 | 0.000030 | 0.15 | |
| Molar mass | M(m) | 1.13428913E-04 | 17.0E-12 | kg mol-1 | 0.015 |
| Magnetic moment | mm | 4.4904514E-26 | 15.0E-33 | J T-1 | 0.33 |
| Magnetic moment in Bohr magnetons | mm/mB | 4.84197097E+00 | 710.0E-9 | 0.15 | |
| Magnetic moment in Nuclear magnetons | mm/mN | 8.8905981 | 0.0000013 | 0.15 | |
| Magnetic moment anomaly (mm/((e hbar)/2mm) - 1) | am | 1.1659230E-03 | 8.4E-9 | ||
| g-factor (2 (1 + am)) | gm | 2.002331846 | 0.000000017 | 0.0084 | |
| Muon-proton magnetic moment ratio | mm/mp | 3.18334547 | 0.00000047 | 0.15 | |
| Proton | |||||
| Mass | mp | 1.67E-27 | 1.0E-33 | kg | 0.59 |
| Mass in atomic mass units | 1.007276470 | 0.000000012 | u | 0.012 | |
| Mass in eV | 938.27231 | 0.00028 | MeV | 0.30 | |
| Proton-electron mass ratio | mp/me | 1836.152701 | 0.000037 | 0.02 | |
| Proton-muon mass ratio | mp/mm | 8.8802444 | 0.0000013 | 0.15 | |
| Specific charge | e/mp | 9.5788309E+07 | 29.0E+0 | C kg-1 | 0.30 |
| Molar mass | M(p) | 1.007267470E-03 | 12.0E-12 | kg mol-1 | 0.012 |
| Compton wavelength | lC,p | 1.32141002E-15 | 120.0E-24 | m | 0.089 |
| Compton wavelength over 2p | lbarC,p | 2.10308937E-16 | 19.0E-24 | m | 0.089 |
| Magnetic moment | mp | 1.41060761E-26 | 4.7E-33 | J T-1 | 0.34 |
| Magnetic moment in Bohr magnetons | mp/mB | 1.521032202E-03 | 15.0E-12 | 0.010 | |
| Magnetic moment in Nuclear magnetons | mp/mN | 2.792847386 | 0.000000063 | 0.023 | |
| Diamagnetic shielding correction for protons (H2O, spherical sample, 25C) 1-mp'/mp | sH2O | 2.5689E-05 | 15.0E-9 | ||
| Shielded proton moment (H2O,spherical sample, 25C) | mp' | 1.41057138E-26 | 4.7E-33 | J T-1 | 0.34 |
| Shielded proton moment in Bohr magnetons | mp'/mB | 1.520993129E-03 | 17.0E-12 | 0.011 | |
| Shielded proton moment in Nuclear magnetons | mp'/mN | 2.792775642 | 64.0E-9 | 0.023 | |
| Gyromagnetic ratio | gp | 267522128 | 81 | s-1 T-1 | 0.30 |
| Gyromagnetic ratio over 2p | gp/2p | 42.577469 | 0.000013 | MHz T-1 | 0.30 |
| Gyromagnetic ratio (uncorrected, H2O,spherical sample,25C) | gp' | 267515255 | 81 | s-1 T-1 | 0.30 |
| Gyromagnetic ratio over 2p(uncorrected, H2O,spherical sample,25C) | gp'/2p | 42.576375 | 0.000013 | MHz T-1 | 0.30 |
| Neutron | |||||
| Mass | mn | 1.6749286E-27 | 1.0E-33 | kg | 0.59 |
| Mass in atomic mass units | 1.008664904 | 0.000000014 | u | 0.014 | |
| Mass in eV | 939.56563 | 0.00028 | MeV | 0.30 | |
| Neutron-electron mass ratio | mn/me | 1838.683662 | 0.000040 | 0.022 | |
| Neutron-proton mass ratio | mn/mp | 1.001378404 | 0.000000009 | 0.009 | |
| Molar mass | M(n) | 1.008664904E-03 | 14.0E-12 | kg mol-1 | 0.014 |
| Compton wavelength | lC,n | 1.31959110E-15 | 120.0E-24 | m | 0.089 |
| Compton wavelength over 2p | lbarC,n | 2.10019445E-16 | 19.0E-24 | m | 0.089 |
| Magnetic moment (scalar magnitude) | mn | 9.66237070E-27 | 4.0E-33 | J T-1 | 0.41 |
| Magnetic moment in Bohr magnetons | mn/mB | 1.04187563E-03 | 250.0E-12 | 0.24 | |
| Magnetic moment in Nuclear magnetons | mn/mN | 1.91304275 | 0.00000045 | 0.24 | |
| Neutron-electron magnetic moment ratio | mn/me | 1.04066882E-03 | 250.0E-12 | 0.24 | |
| Neutron-proton magnetic moment ratio | mn/mp | 0.68497934 | 0.00000016 | 0.24 | |
| Deuteron | |||||
| Mass | md | 3.3483586E-27 | 2.0E-33 | kg | 0.59 |
| Mass in atomic mass units | 2.013553214 | 0.000000024 | u | 0.012 | |
| Mass in eV | 1875.61339 | 0.00057 | MeV | 0.30 | |
| Deuteron-electron mass ratio | md/me | 3670.483014 | 75.0E-6 | 0.020 | |
| Deuteron-proton mass ratio | md/mp | 1.999007496 | 6.0E-9 | 0.003 | |
| Molar mass | M(d) | 2.013553214E-03 | 24.0E-12 | kg mol-1 | 0.012 |
| Magnetic moment | md | 4.3307375E-27 | 1.5E-33 | J T-1 | 0.34 |
| Magnetic moment in Bohr magnetons | md/mB | 4.669754479E-04 | 9.1E-12 | 0.019 | |
| Magnetic moment in Nuclear magnetons | md/mN | 0.857438230 | 0.000000024 | 0.028 | |
| Deuteron-electron magnetic moment ratio | md/me | 4.66434546E-04 | 9.1E-12 | 0.019 | |
| Deuteron-proton magnetic moment ratio | md/mp | 0.307012204 | 5.1E-9 | 0.017 | |
| Physicochemical constants | |||||
| Avogadro constant | NA,L | 6.0221367E+23 | 360.0E+15 | mol-1 | 0.59 |
| Atomic mass constant, m(12C)/12 | mu | 1.6605402E-27 | 1.0E-33 | kg | 0.59 |
| Atomic mass constant in eV | 931.49432 | 0.00028 | MeV | 0.30 | |
| Faraday constant | F | 96485.309 | 29.0E-3 | C mol-1 | 0.30 |
| Molar Planck constant | NAh | 3.99031323E-10 | 36.0E-18 | J s mol-1 | 0.089 |
| NAhc | 0.11962658 | 11.0E-9 | J m mol-1 | 0.089 | |
| Molar gas constant | R | 8.314510 | 0.000070 | J mol-1 K-1 | 8.4 |
| Boltzmann constant | k | 1.380658E-23 | 120.0E-30 | J K-1 | 8.4 |
| Boltzmann constant in eV | 8.617385E-05 | 730.0E-12 | eV K-1 | 8.4 | |
| Boltzmann constant in hertz | 2.083674E+10 | 180.0E+3 | Hz K-1 | 8.4 | |
| Boltzmann constant in wavenumbers | 69.50387 | 0.00059 | m-1 K-1 | 8.4 | |
| Molar volume (ideal gas),RT/p (at 273.15K, 101325 Pa) | Vm | 22414.10 | 0.19 | cm3 mol-1 | 8.4 |
| Loschmidt constant NA/Vm | n0 | 2.686763E+25 | 230.0E+18 | m-3 | 8.5 |
| Stefan-Boltzmann constant (p2/60)k4/hbar3c2 | s | 5.67051E-08 | 1.9E-12 | W m-2 K-4 | 34 |
| First radiation constant 2phc2 | c1 | 3.7417749E-16 | 220.0E-24 | W m2 | 0.60 |
| Second radiation constant hc/k | c2 | 0.01438769 | 120.0E-9 | m K | 8.4 |
| Wien displacement law constant | b | 2.897756E-03 | 24.0E-9 | m K | 8.4 |
| Conversion factors and units | |||||
| Electron volt | eV | 1.60217733E-19 | 49.0E-27 | J | 0.30 |
| Atomic mass unit (unified) | u | 1.6605402E-27 | 1.0E-33 | kg | 0.59 |
| Standard atmosphere | atm | 101325 | Pa | exact | |
| Standard acceleration of gravity | gn | 9.80665 | m s-2 | exact | |
| As-maintained electrical units | |||||
| BIPM-maintained ohm,W69-BI as of 1 Jan 1985 | WBI85 | 0.999998437 | 0.000000050 | W | 0.050 |
| drift rate of W69-BI | dW69-BI/dt | -0.0566 | 0.0015 | mW / yr | |
| BIPM-maintained volt, 483594 GHz(h/2e) | V76-BI | 0.99999241 | 0.00000030 | V | 0.30 |
| BIPM-maintained ampere, ABIPM=V76-BI/W69-BI | ABI85 | 0.99999397 | 0.00000030 | A | 0.30 |
| X-ray standards | |||||
| Cu x-unit:l(CuKa1)=1537.400 xu | xu(CuKa1) | 1.00207789E-13 | 70.0E-21 | m | 0.70 |
| Mo x-unit:l(MoKa1)=707.831 xu | xu(MoKa1) | 1.00209938E-13 | 45.0E-21 | m | 0.45 |
| A *:=l(WKa1)=0.2090100A* | A* | 1.00001481E-10 | 92.0E-18 | m | 0.92 |
| Lattice spacing of Si(in vacuum, 22.5C) | a | 0.54310196 | 0.00000011 | nm | 0.21 |
| d220=a/(8)0.5 | d220 | 0.192015540 | 0.000000040 | nm | 0.21 |
| Molar volume of Si, M(Si)/r(Si)=NAa3/8 | Vm(Si) | 12.0588179 | 0.0000089 | cm3 mol-1 | 0.74 |