Table of universal constants

Quantity	Symbol	Value¹ (SI units)	Relative Standard Uncertainty	Reference
characteristic impedance of vacuum	$Z_0 = \mu_0 c \,$	376.730 313 461... Ω	defined	a
electric constant	$\varepsilon_0 = 1 / ( \mu_0 c^2 )\,$	8.854 187 817... × 10^-12F·m^-1	defined	a
magnetic constant	$\mu_0 \,$	4π × 10^-7 N·A^-2 = 1.2566 370 614... × 10^-6 N·A^-2	defined	a
Newtonian constant of gravitation	$G \,$	6.6742(10) × 10^-11m³·kg^-1·s^-2	1.5 × 10^-4	a
Planck's constant	$h \,$	6.626 0693(11) × 10^-34 J·s	1.7 × 10^-7	a
Dirac's constant	$\hbar = h / (2 \pi)$	1.054 571 68(18) × 10^-34 J·s	1.7 × 10^-7	a
Planck length	$l_P = (\hbar G / c^3)^ \frac{1}{2} \,$	1.616 24(12) × 10^-35 m	7.5 × 10^-5	a
Planck mass	$m_P = ( \hbar c / G )^ \frac{1}{2} \,$	2.176 45(16) × 10^-8 kg	7.5 × 10^-5	a
Planck temperature	$T_P = ( \hbar c^5 / G )^ \frac{1}{2} / k$	1.416 79(11) × 10³² K	7.5 × 10^-5	a
Planck time	$t_P = (\hbar G / c^5)^ \frac{1}{2}$	5.391 21(40) × 10^-44 s	7.5 × 10^-5	a
speed of light in vacuum	$c \,$	299 792 458 m·s^-1	defined	a

Table of electromagnetic constants

Quantity	Symbol	Value¹ (SI units)	Relative Standard Uncertainty	Reference
Bohr magneton	$\mu_B = e \hbar / 2 m_e$	927.400 949(80) × 10^-26 J·T^-1	8.6 × 10^-8	a
conductance quantum	$G_0 = 2 e^2 / h \,$	7.748 091 733(26) × 10^-5 S	3.3 × 10^-9	a
Coulomb's constant	$\kappa = 1 / 4\pi\varepsilon_0 \,$	8.987 742 438 × 10⁹ N·m²C^-2
elementary charge (electron charge)	$e \,\!$	1.602 176 53(14) × 10^-19 C	8.5 × 10^-8	a
Josephson constant	$K_J = 2 e / h \,$	483 597.879(41) × 10⁹ Hz· V^-1	8.5 × 10^-8	a
magnetic flux quantum	$\phi_0 = h / 2 e \,$	2.067 833 72(18) × 10^-15 Wb	8.5 × 10^-8	a
nuclear magneton	$\mu_N = e \hbar / 2 m_p$	5.050 783 43(43) × 10^-27 J·T^-1	8.6 × 10^-8	a
resistance quantum	$R_0 = h / 2 e^2 \,$	12 906.403 725(43) Ω	3.3 × 10^-9	a
von Klitzing constant	$R_K = h / e^2 \,$	25 812.807 449(86) Ω	3.3 × 10^-9	a

Table of atomic and nuclear constants

Quantity		Symbol	Value¹ (SI units)	Relative Standard Uncertainty	Reference
alpha particle	mass²	$m_\alpha \,$	6.644 6565(11) × 10^-27 kg	1.7 × 10^-7	a
Bohr radius		$a_0 = \alpha / 4 \pi R_\infin \,$	0.529 177 2108(18) × 10^-10 m	3.3 × 10^-9	a
deuteron	magnetic moment	$\mu_d \,$	0.433 073 482(38) × 10^-26 J · T^-1	8.7 × 10^-8	a
	mass²	$m_d \,$	3.343 583 35(57) × 10^-27 kg	1.7 × 10^-7	a
	rms charge radius	$R_d \,$	2.1394 × 10^-15 m	1.3 × 10^-3	a
electron	classical radius	$r_e = \alpha^2 a_0 \,$	2.817 940 325(28) × 10^-15 m	1.0 × 10^-8	a
	Compton wavelength	$\lambda_C = h / m_e c \,$	2.426 310 238(16) × 10^-12 m	6.7 × 10^-9	a
	g factor (Lande g factor)	$g_e = 2 \mu_e / \mu_B \,$	-2.002 319 304 3718(75)	3.8 × 10^-12	a
	gyromagnetic ratio	$\gamma_e = 2 \|\mu_e\| / \hbar$	1.760 859 74(15) × 10¹¹ s^-1 T^-1	8.6 × 10^-8	a
	magnetic moment	$\mu_e \,$	-928.476 412(80) × 10^-26 J·T^-1	8.6 × 10^-8	a
	mass²	$m_e \,$	9.109 3826(16) × 10^-31 kg	1.7 × 10^-7	a
Fermi coupling constant			1.166 39(1) × 10^-5 GeV^-2	8.6 × 10^-6	a
fine-structure constant			7.297 352 568(24) × 10^-3	3.3 × 10^-9	a
fine-structure constant			137.035 999 11(46)	3.3 × 10^-9	a
Hartree energy			4.359 744 17(75) × 10^-18 J	1.7 × 10^-7	a
helion	mass²		5.006 412 14(86) × 10^-27 kg	1.7 × 10^-7	a
	shielded gyromagnetic ratio		2.037 894 70(18) × 10⁸ s^-1 T^-1	8.7 × 10^-8	a
	shielded magnetic moment		-1.074 553 024(93) × 10^-26 J · T^-1	8.7 × 10^-8	a
muon	Compton wavelength	$\lambda_{C,\mu} = h / m_\mu c \,$	11.734 441 05(30) × 10^-15 m	2.5 × 10^-8	a
	g factor	$g_\mu \,$	-2.002 331 8396(12)	6.2 × 10^-10	a
	magnetic moment	$\mu_\mu \,$	-4.490 447 99(40) × 10^-26 J · T^-1	8.9 × 10^-8	a
	magnetic moment anomaly	$a_\mu = \|\mu_\mu\| / (e \hbar / 2 m_\mu) - 1$	1.165 919 81(62) × 10^-3	5.3 × 10^-7	a
	mass²	$m_\mu \,$	1.883 531 40(33) × 10^-28 kg	1.7 × 10^-7	a
neutron	Compton wavelength	$\lambda_{C,n} = h / m_n c \,$	1.319 590 9067(88) × 10^-15 m	6.7 × 10^-9	a
	g factor	$g_n = 2 \mu_n / \mu_N \,$	-3.826 085 46(90)	2.4 × 10^-7	a
	gyromagnetic ratio	$\gamma_n = 2 \|\mu_n\| / \hbar$	1.832 471 83(46) × 10⁸ s^-1 T^-1	2.5 × 10^-7	a
	magnetic moment	$\mu_n \,$	-0.966 236 45(24) × 10^-26 J · T^-1	2.5 × 10^-7	a
	mass²	$m_n \,$	1.674 927 28(29) × 10^-27 kg	1.7 × 10^-7	a
proton	Compton wavelength	$\lambda_{C,p} = h /m_p c \,$	1.321 409 8555(88) × 10^-15 m	6.7 × 10^-9	a
	g factor	$g_p = 2 \mu_p / \mu_N \,$	5.585 694 701(56)	1.0 × 10^-8	a
	gyromagnetic ratio	$\gamma_p = 2 \mu_P / \hbar$	2.675 222 05(23) × 10⁸ s^-1·T^-1	8.6 × 10^-8	a
	magnetic moment	$\mu_p \,$	1.410 606 71(12) × 10^-26 J·T^-1	8.7 × 10^-8	a
	mass²	$m_p \,$	1.672 621 71(29) × 10^-27 kg	1.7 × 10^-7	a
	shielded gyromagnetic ratio	$\gamma_p^' = 2 \mu_p^' / \hbar$	2.675 153 33(23) × 10⁸ s^-1 T^-1	8.6 × 10^-8	a
	shielded magnetic moment	$\mu_p^'$	1.410 570 47(12) × 10^-26 J · T^-1	8.7 × 10^-8	a
quantum of circulation		$h / 2 m_e \,$	3.636 947 550(24) × 10^-4 m² s^-1	6.7 × 10^-9	a
Rydberg constant		$R_\infin = \alpha^2 m_e c / 2 h \,$	10 973 731.568 525(73) m^-1	6.6 × 10^-12	a
tauon	Compton wavelength	$\lambda_{C,\tau} = h / m_\tau c \,$	0.697 72(11) × 10^-15 m	1.6 × 10^-4	a
tauon	mass²	$m_\tau \,$	3.167 77(52) × 10^-27 kg	1.6 × 10^-4	a
Thomson cross section		$(8 \pi / 3)r_e^2$	0.665 245 873(13) × 10^-28 m²	2.0 × 10^-8	a
weak mixing angle		$\sin^2 \theta_W = 1 - (m_W / m_Z)^2 \,$	0.222 15(76)	3.4 × 10^-3	a

Table of physico-chemical constants

Quantity		Symbol	Value¹ (SI units)	Relative Standard Uncertainty	Reference
atomic mass constant (unified atomic mass unit)		$m_u = 1 u \,$	1.660 538 86(28) × 10^-27 kg	1.7 × 10^-7	a
Avogadro's number		$N_A, L \,$	6.022 1415(10) × 10²³	1.7 × 10^-7	a
Boltzmann constant		$k = R / N_A \,$	1.380 6505(24) × 10^-23 J·K^-1	1.8 × 10^-6	a
Faraday constant		$F = N_A e \,$	96 485.3383(83)C·mol^-1	8.6 × 10^-8	a
first radiation constant		$c_1 = 2 \pi h c^2 \,$	3.741 771 38(64) × 10^-16 W·m²	1.7 × 10^-7	a
first radiation constant	for spectral radiance	$c_{1L} \,$	1.191 042 82(20) × 10^-16 W · m² sr^-1	1.7 × 10^-7	a
Loschmidt constant	at $T$ =273.15 K and $p$ =101.325 kPa	$n_0 = N_A / V_m \,$	2.686 7773(47) × 10²⁵ m^-3	1.8 × 10^-6	a
gas constant		$R \,$	8.314 472(15) J·K^-1·mol^-1	1.7 × 10^-6	a
molar Planck constant		$N_A h \,$	3.990 312 716(27) × 10^-10 J · s · mol^-1	6.7 × 10^-9	a
molar volume of an ideal gas	at $T$ =273.15 K and $p$ =100 kPa		22.710 981(40) × 10^-3 m³ ·mol^-1	1.7 × 10^-6	a
molar volume of an ideal gas	at $T$ =273.15 K and $p$ =101.325 kPa		22.413 996(39) × 10^-3 m³ ·mol^-1	1.7 × 10^-6	a
Sackur-Tetrode constant	at $T$ =1 K and $p$ =100 kPa	$S_0 / R = \frac{5}{2}$ $+ \ln\left[ (2\pi m_u k T / h^2)^{3/2} k T / p \right]$	-1.151 7047(44)	3.8 × 10^-6	a
Sackur-Tetrode constant	at $T$ =1 K and $p$ =101.325 kPa		-1.164 8677(44)	3.8 × 10^-6	a
second radiation constant		$c_2 = h c / k \,$	1.438 7752(25) × 10^-2 m·K	1.7 × 10^-6	a
Stefan-Boltzmann constant		$\sigma = (\pi^2 / 60) k^4 / \hbar^3 c^2$	5.670 400(40) × 10^-8 W·m^-2·K^-4	7.0 × 10^-6	a
Wien displacement law constant		$b = (h c / k) / \,$ 4.965 114 231...	2.897 7685(51) × 10^-3 m · K	1.7 × 10^-6	a

Table of adopted values

Quantity		Symbol	Value (SI units)	Relative Standard Uncertainty	Reference
conventional value of Josephson constant³		$K_{J-90} \,$	483 597.9 × 10⁹ Hz · V^-1	defined	a
conventional value of von Klitzing constant⁴		$R_{K-90} \,$	25 812.807 Ω	defined	a
molar mass	constant	$M_u = M(\,^{12}\mbox{C}) / 12$	1 × 10^-3 kg · mol^-1	defined	a
molar mass	of carbon-12	$M(\,^{12}\mbox{C}) = N_A m(\,^{12}\mbox{C})$	12 × 10^-3 kg · mol⁻¹	defined	a
standard acceleration of gravity (gee, free fall on Earth)		$g_n \,\!$	9.806 65 m·s^-2	defined	a
standard atmosphere		$atm \,$	101 325 Pa	defined	a

Notes

¹the 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.
²the given value is for rest mass.
³This is the value adopted internationally for realizing representations of the volt using the Josephson effect.
⁴This is the value adopted internationally for realizing representations of the ohm using the quantum Hall effect.

Physical Constants

Quantity	Value
speed of light (c)	299,792.458 kilometers/second
gravitational constant (G)	6.6726× 10^-11 m³ /(kg sec²)
Boltzmann constant (k)	1.380658 × 10^-23 Joules/Kelvin
Stefan-Boltzmann constant (s)	5.67051× 10^-8 J/(m² K⁴ s)
Wien's law constant	2.897756× 10⁶ nanometers Kelvin
Planck constant (h)	6.6260755× 10^-34 Joules second
electron mass	9.1093898× 10^-28 grams = 5.48579903× 10^-4 amu
proton mass	1.6726231× 10^-24 grams = 1.007276470 amu
neutron mass	1.6749286× 10^-24 grams = 1.008664904 amu
deuterium nucleus mass	3.3435860× 10^-24 grams = 2.013553214 amu