Quantity
Symbol
Value
Relative Standard Uncertainty
characteristic impedance of vacuum
Z
0
=
μ
0
c
{\displaystyle Z_{0}=\mu _{0}c\,}
376.730 313 461... Ω
defined
electric constant (permittivity of free space)
ε
0
=
1
/
(
μ
0
c
2
)
{\displaystyle \varepsilon _{0}=1/(\mu _{0}c^{2})\,}
8.854 187 817... × 10-12 F·m-1
defined
magnetic constant (permeability of free space )
μ
0
{\displaystyle \mu _{0}\,}
4π × 10-7 N·A-2 = 1.2566 370 614... × 10-6 N·A-2
defined
gravitational constant (Newtonian constant of gravitation)
G
{\displaystyle G\,}
6.6742(10) × 10-11 m3 ·kg-1 ·s-2
1.5 × 10-4
Planck's constant
h
{\displaystyle h\,}
6.626 0693(11) × 10-34 J·s
1.7 × 10-7
Dirac's constant
ℏ
=
h
/
(
2
π
)
{\displaystyle \hbar =h/(2\pi )}
1.054 571 68(18) × 10-34 J·s
1.7 × 10-7
speed of light in vacuum
c
{\displaystyle c\,}
299 792 458 m·s-1
defined
Quantity
Symbol
Value1 (SI units)
Relative Standard Uncertainty
Bohr magneton
μ
B
=
e
ℏ
/
2
m
e
{\displaystyle \mu _{B}=e\hbar /2m_{e}}
927.400 949(80) × 10-26 J·T-1
8.6 × 10-8
conductance quantum
G
0
=
2
e
2
/
h
{\displaystyle G_{0}=2e^{2}/h\,}
7.748 091 733(26) × 10-5 S
3.3 × 10-9
Coulomb's constant
κ
=
1
/
4
π
ε
0
{\displaystyle \kappa =1/4\pi \varepsilon _{0}\,}
8.987 742 438 × 109 N·m2 C-2
defined
elementary charge
e
{\displaystyle e\,}
1.602 176 53(14) × 10-19 C
8.5 × 10-8
Josephson constant
K
J
=
2
e
/
h
{\displaystyle K_{J}=2e/h\,}
483 597.879(41) × 109 Hz· V-1
8.5 × 10-8
magnetic flux quantum
ϕ
0
=
h
/
2
e
{\displaystyle \phi _{0}=h/2e\,}
2.067 833 72(18) × 10-15 Wb
8.5 × 10-8
nuclear magneton
μ
N
=
e
ℏ
/
2
m
p
{\displaystyle \mu _{N}=e\hbar /2m_{p}}
5.050 783 43(43) × 10-27 J·T-1
8.6 × 10-8
resistance quantum
R
0
=
h
/
2
e
2
{\displaystyle R_{0}=h/2e^{2}\,}
12 906.403 725(43) Ω
3.3 × 10-9
von Klitzing constant
R
K
=
h
/
e
2
{\displaystyle R_{K}=h/e^{2}\,}
25 812.807 449(86) Ω
3.3 × 10-9
Quantity
Symbol
Value1 (SI units)
Relative Standard Uncertainty
Bohr radius
a
0
=
α
/
4
π
R
∞
{\displaystyle a_{0}=\alpha /4\pi R_{\infty }\,}
0.529 177 2108(18) × 10-10 m
3.3 × 10-9
Fermi coupling constant
G
F
/
(
ℏ
c
)
3
{\displaystyle G_{F}/(\hbar c)^{3}}
1.166 39(1) × 10-5 GeV-2
8.6 × 10-6
fine structure constant
α
=
μ
0
e
2
c
/
(
2
h
)
=
e
2
/
(
4
π
ε
0
ℏ
c
)
{\displaystyle \alpha =\mu _{0}e^{2}c/(2h)=e^{2}/(4\pi \varepsilon _{0}\hbar c)\,}
7.297 352 568(24) × 10-3
3.3 × 10-9
Hartree energy
E
h
=
2
R
∞
h
c
{\displaystyle E_{h}=2R_{\infty }hc\,}
4.359 744 17(75) × 10-18 J
1.7 × 10-7
quantum of circulation
h
/
2
m
e
{\displaystyle h/2m_{e}\,}
3.636 947 550(24) × 10-4 m2 s-1
6.7 × 10-9
Rydberg constant
R
∞
=
α
2
m
e
c
/
2
h
{\displaystyle R_{\infty }=\alpha ^{2}m_{e}c/2h\,}
10 973 731.568 525(73) m-1
6.6 × 10-12
Thomson cross section
(
8
π
/
3
)
r
e
2
{\displaystyle (8\pi /3)r_{e}^{2}}
0.665 245 873(13) × 10-28 m2
2.0 × 10-8
Weinberg angle|weak mixing angle
sin
2
θ
W
=
1
−
(
m
W
/
m
Z
)
2
{\displaystyle \sin ^{2}\theta _{W}=1-(m_{W}/m_{Z})^{2}\,}
0.222 15(76)
3.4 × 10-3
Quantity
Symbol
Value1 (SI units)
Relative Standard Uncertainty
atomic mass constant (unified atomic mass unit)
m
u
=
1
u
{\displaystyle m_{u}=1\ u\,}
1.660 538 86(28) × 10-27 kg
1.7 × 10-7
Avogadro's number
N
A
,
L
{\displaystyle N_{A},L\,}
6.0221417(10) × 1023
1.7 × 10-7
Boltzmann constant
k
=
R
/
N
A
{\displaystyle k=R/N_{A}\,}
1.380 6505(24) × 10-23 J·K-1
1.8 × 10-6
Faraday constant
F
=
N
A
e
{\displaystyle F=N_{A}e\,}
96 485.3383(83)C·mol-1
8.6 × 10-8
first radiation constant
c
1
=
2
π
h
c
2
{\displaystyle c_{1}=2\pi hc^{2}\,}
3.741 771 38(64) × 10-16 W·m2
1.7 × 10-7
for spectral radiance
c
1
L
{\displaystyle c_{1L}\,}
1.191 042 82(20) × 10-16 W · m2 sr-1
1.7 × 10-7
Loschmidt constant
at
T
{\displaystyle T}
=273.15 K and
p
{\displaystyle p}
=101.325 kPa
n
0
=
N
A
/
V
m
{\displaystyle n_{0}=N_{A}/V_{m}\,}
2.686 7773(47) × 1025 m-3
1.8 × 10-6
gas constant
R
{\displaystyle R\,}
8.314 472(15) J·K-1 ·mol-1
1.7 × 10-6
molar Planck constant
N
A
h
{\displaystyle N_{A}h\,}
3.990 312 716(27) × 10-10 J · s · mol-1
6.7 × 10-9
molar volume of an ideal gas
at
T
{\displaystyle T}
=273.15 K and
p
{\displaystyle p}
=100 kPa
V
m
=
R
T
/
p
{\displaystyle V_{m}=RT/p\,}
22.710 981(40) × 10-3 m3 ·mol-1
1.7 × 10-6
at
T
{\displaystyle T}
=273.15 K and
p
{\displaystyle p}
=101.325 kPa
22.413 996(39) × 10-3 m3 ·mol-1
1.7 × 10-6
Sackur-Tetrode constant
at
T
{\displaystyle T}
=1 K and
p
{\displaystyle p}
=100 kPa
S
0
/
R
=
5
2
{\displaystyle S_{0}/R={\frac {5}{2}}}
+
ln
[
(
2
π
m
u
k
T
/
h
2
)
3
/
2
k
T
/
p
]
{\displaystyle +\ln \left[(2\pi m_{u}kT/h^{2})^{3/2}kT/p\right]}
-1.151 7047(44)
3.8 × 10-6
at
T
{\displaystyle T}
=1 K and
p
{\displaystyle p}
=101.325 kPa
-1.164 8677(44)
3.8 × 10-6
second radiation constant
c
2
=
h
c
/
k
{\displaystyle c_{2}=hc/k\,}
1.438 7752(25) × 10-2 m·K
1.7 × 10-6
Stefan-Boltzmann constant
σ
=
(
π
2
/
60
)
k
4
/
ℏ
3
c
2
{\displaystyle \sigma =(\pi ^{2}/60)k^{4}/\hbar ^{3}c^{2}}
5.670 400(40) × 10-8 W·m-2 ·K-4
7.0 × 10-6
Wien displacement law constant
b
=
(
h
c
/
k
)
/
{\displaystyle b=(hc/k)/\,}
4.965 114 231...
2.897 7685(51) × 10-3 m · K
1.7 × 10-6
Quantity
Symbol
Value (SI units)
Relative Standard Uncertainty
conventional value of Josephson constant2
K
J
−
90
{\displaystyle K_{J-90}\,}
483 597.9 × 109 Hz · V-1
defined
conventional value of von Klitzing constant3
R
K
−
90
{\displaystyle R_{K-90}\,}
25 812.807 Ω
defined
molar mass
constant
M
u
=
M
(
12
C
)
/
12
{\displaystyle M_{u}=M(\,^{12}{\mbox{C}})/12}
1 × 10-3 kg · mol-1
defined
of carbon-12
M
(
12
C
)
=
N
A
m
(
12
C
)
{\displaystyle M(\,^{12}{\mbox{C}})=N_{A}m(\,^{12}{\mbox{C}})}
12 × 10-3 kg · mol−1
defined
standard acceleration of gravity (free fall on Earth)
g
n
{\displaystyle g_{n}\,\!}
9.806 65 m·s-2
defined
standard atmosphere
atm
{\displaystyle {\mbox{atm}}\,}
101 325 Pa
defined
1 The values are given in the so-called concise form ; the number in brackets is the standard uncertainty , which is the value multiplied by the relative standard uncertainty .
2 This is the value adopted internationally for realizing representations of the volt using the Josephson effect.
3 This is the value adopted internationally for realizing representations of the ohm using the quantum Hall effect.