75 constants from the 2022 CODATA adjustment. Values are exact as published; a blank uncertainty means the constant is exact by definition.
Universal
Quantity
Symbol
Value
Uncertainty
Unit
speed of light in vacuum
c
299 792 458
exact
m·s−1
Newtonian constant of gravitation
G
6.674 30 e-11
0.000 15 e-11
m3·kg−1·s−2
Planck constant
h
6.626 070 15 e-34
exact
J·Hz−1
reduced Planck constant
ħ
1.054 571 817... e-34
exact
J·s
Planck constant in eV/Hz
h
4.135 667 696... e-15
exact
eV·Hz−1
vacuum electric permittivity
ε₀
8.854 187 8188 e-12
0.000 000 0014 e-12
F·m−1
vacuum magnetic permeability
μ₀
1.256 637 061 27 e-6
0.000 000 000 20 e-6
N·A−2
characteristic impedance of vacuum
Z₀
376.730 313 412
0.000 000 059
ohm
Planck length
lP
1.616 255 e-35
0.000 018 e-35
m
Planck mass
mP
2.176 434 e-8
0.000 024 e-8
kg
Planck time
tP
5.391 247 e-44
0.000 060 e-44
s
Planck temperature
TP
1.416 784 e32
0.000 016 e32
K
Electromagnetic
Quantity
Symbol
Value
Uncertainty
Unit
elementary charge
e
1.602 176 634 e-19
exact
C
magnetic flux quantum
Φ₀
2.067 833 848... e-15
exact
Wb
conductance quantum
G₀
7.748 091 729... e-5
exact
S
Josephson constant
KJ
483 597.848 4... e9
exact
Hz·V−1
von Klitzing constant
RK
25 812.807 45...
exact
ohm
Bohr magneton
μB
9.274 010 0657 e-24
0.000 000 0029 e-24
J·T−1
nuclear magneton
μN
5.050 783 7393 e-27
0.000 000 0016 e-27
J·T−1
electron magnetic moment
μe
-9.284 764 6917 e-24
0.000 000 0029 e-24
J·T−1
proton magnetic moment
μp
1.410 606 795 45 e-26
0.000 000 000 60 e-26
J·T−1
neutron magnetic moment
μn
-9.662 3653 e-27
0.000 0023 e-27
J·T−1
electron g factor
ge
-2.002 319 304 360 92
0.000 000 000 000 36
Atomic and nuclear
Quantity
Symbol
Value
Uncertainty
Unit
fine-structure constant
α
7.297 352 5643 e-3
0.000 000 0011 e-3
inverse fine-structure constant
1/α
137.035 999 177
0.000 000 021
Rydberg constant
R∞
10 973 731.568 157
0.000 012
m−1
Rydberg constant times hc in eV
R∞hc
13.605 693 122 990
0.000 000 000 015
eV
Bohr radius
a₀
5.291 772 105 44 e-11
0.000 000 000 82 e-11
m
Hartree energy
Eh
4.359 744 722 2060 e-18
0.000 000 000 0048 e-18
J
Hartree energy in eV
Eh
27.211 386 245 981
0.000 000 000 030
eV
classical electron radius
re
2.817 940 3205 e-15
0.000 000 0013 e-15
m
Thomson cross section
σe
6.652 458 7051 e-29
0.000 000 0062 e-29
m2
Compton wavelength
λC
2.426 310 235 38 e-12
0.000 000 000 76 e-12
m
electron mass
me
9.109 383 7139 e-31
0.000 000 0028 e-31
kg
electron mass energy equivalent in MeV
mec²
0.510 998 950 69
0.000 000 000 16
MeV
proton mass
mp
1.672 621 925 95 e-27
0.000 000 000 52 e-27
kg
proton mass energy equivalent in MeV
mpc²
938.272 089 43
0.000 000 29
MeV
neutron mass
mn
1.674 927 500 56 e-27
0.000 000 000 85 e-27
kg
neutron mass energy equivalent in MeV
mnc²
939.565 421 94
0.000 000 48
MeV
deuteron mass
md
3.343 583 7768 e-27
0.000 000 0010 e-27
kg
alpha particle mass
mα
6.644 657 3450 e-27
0.000 000 0021 e-27
kg
muon mass
mμ
1.883 531 627 e-28
0.000 000 042 e-28
kg
proton-electron mass ratio
mp/m_e
1836.152 673 426
0.000 000 032
proton rms charge radius
rp
8.4075 e-16
0.0064 e-16
m
atomic mass constant
mu
1.660 539 068 92 e-27
0.000 000 000 52 e-27
kg
atomic mass constant energy equivalent in MeV
muc²
931.494 103 72
0.000 000 29
MeV
Physico-chemical
Quantity
Symbol
Value
Uncertainty
Unit
Avogadro constant
NA
6.022 140 76 e23
exact
mol−1
Boltzmann constant
k
1.380 649 e-23
exact
J·K−1
Boltzmann constant in eV/K
k
8.617 333 262... e-5
exact
eV·K−1
molar gas constant
R
8.314 462 618...
exact
J·mol−1·K−1
Faraday constant
F
96 485.332 12...
exact
C·mol−1
molar volume of ideal gas (273.15 K, 101.325 kPa)
Vm
22.413 969 54... e-3
exact
m3·mol−1
Loschmidt constant (273.15 K, 101.325 kPa)
n₀
2.686 780 111... e25
exact
m−3
Stefan-Boltzmann constant
σ
5.670 374 419... e-8
exact
W·m−2·K−4
Wien wavelength displacement law constant
b
2.897 771 955... e-3
exact
m·K
Wien frequency displacement law constant
b′
5.878 925 757... e10
exact
Hz·K−1
first radiation constant
c₁
3.741 771 852... e-16
exact
W·m2
second radiation constant
c₂
1.438 776 877... e-2
exact
m·K
molar Planck constant
NAh
3.990 312 712... e-10
exact
J·Hz−1·mol−1
Adopted exact values
Quantity
Symbol
Value
Uncertainty
Unit
standard acceleration of gravity
gn
9.806 65
exact
m·s−2
standard atmosphere
atm
101 325
exact
Pa
standard-state pressure
100 000
exact
Pa
hyperfine transition frequency of Cs-133
ΔνCs
9 192 631 770
exact
Hz
luminous efficacy
Kcd
683
exact
lm·W−1
electron volt
eV
1.602 176 634 e-19
exact
J
Unit relationships
Quantity
Symbol
Value
Uncertainty
Unit
electron volt-joule relationship
1.602 176 634 e-19
exact
J
joule-electron volt relationship
6.241 509 074... e18
exact
eV
atomic mass unit-kilogram relationship
1.660 539 068 92 e-27
0.000 000 000 52 e-27
kg
atomic mass unit-electron volt relationship
9.314 941 0372 e8
0.000 000 0029 e8
eV
kilogram-joule relationship
8.987 551 787... e16
exact
J
kelvin-joule relationship
1.380 649 e-23
exact
J
kelvin-electron volt relationship
8.617 333 262... e-5
exact
eV
hertz-joule relationship
6.626 070 15 e-34
exact
J
hertz-electron volt relationship
4.135 667 696... e-15
exact
eV
inverse meter-joule relationship
1.986 445 857... e-25
exact
J
Values from the CODATA 2022 adjustment, published by NIST — a work of the United States government and in the public domain. The complete listing of 355 constants is at
physics.nist.gov/cuu/Constants.