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List of Physical Constants

List Physical Constants

This database gives values of the basic constants and conversion factors of physics and chemistry resulting from the 2022 least-squares adjustment of the fundamental physical constants as published by the CODATA Task Group on Fundamental Constants and recommended for international use by CODATA.

The constants listed here are the values of physical constants and are expressed in SI units.

Quantity	Symbol	Numerical value	Unit
Speed of light in vacuum	c	299,792,458 (exact)	m-s-1
Newtonian constant of gravitation	G	6.67430(15) x 10-11	m3-kg-1-s-2
Plank constant	ħ	6.626070 15 × 10−34 (exact)	J Hz −1
in eV's		4.135667 696. . . × 10−15	eV Hz −1
	ħ	1.054571 817. . . × 10−34	J s
in eV's		6.582119 569. . . × 10−16	eV s
elementary charge	e	1.602176 634 × 10−19 (exact)	C
vacuum magnetic permeability 4παħ/e2c	µ0	1.256637 06212(19)× 10−6	N A−2
µ0/(4π × 10−7)	µ0	1.00000000055(15)	N A−2
vacuum electric permittivity 1/µ0c 2	ϵ0	8.854187 8128(13)× 10−12	F m −1
Josephson constant 2e/h	KJ	483597.848 4. . . × 109	Hz V−1
von Klitzing constant µ0c/2α =2πħ/e2	RK	25812.807 45. . .	Ω
magnetic flux quantum 2πħ/(2e)	Φ0	2.067833 848. . . × 10−15	Wb
Bohr magneton eħ/2me	µB	9.274010 0783(28)× 10−24	J T−1
in eV T−1	µB	5.788381 8060(17)× 10−5	eV T−1
nuclear magneton eħ/2mp	µN	5.050783 7461(15)× 10−27	J T−1
in eV T−1	µN	3.152451 25844(96)× 10-8	eV T−1
fine-structure constant e2/4πϵ0ħc	α	7.297352 5693(11)× 10−3
inverse fine-structure constant	α-1	137.035999 084(21)
Rydberg frequency α2 mec2/2h = Eh/2h	cR∞	3.289841 9602508(64)× 1015	Hz
energy equivalent in eV	cR∞	13.605693 122994(26)	eV
Rydberg constant	R∞	10973 731.568160(21)	[m −1]
Bohr radius ħ/αmec =4πϵ0ħ2/mee2	α0	5.291772 10903(80)× 10−11	m
Hartree energy α2 mec2 = e2/4πϵ0a0 =2(cR∞)h	Eh	4.359744 7222071(85)× 10−18	J
in eV	Eh	27.211386 245988(53)	eV
electron mass	me	9.109383 7015(28)× 10−31	kg
in u		5.485799 09065(16)× 10−4	u
energy equivalent in MeV	mec 2	0.510998 95000(15)	MeV
electron-muon mass ratio	me/mµ	4.836331 69(11)× 10−3
electron-proton mass ratio	me/mp	5.446170 21487(33)× 10−4
electron charge to mass quotient	−e/me	−1.758820010 76(53)× 1011	C kg −1
reduced Compton wavelength ħ/mec = αa0	λC	3.861592 6796(12)× 10−13	m
Compton wavelength	λC	2.426310 23867(73)× 10−12	[m]
classical electron radius α2 a0	re	2.817940 3262(13)× 10−15	m
Thomson cross section (8π/3)r 2e	σe	6.652458 7321(60)× 10−29	m2
electron magnetic moment	µe	−9.2847647043(28)× 10−24	J T−1
to Bohr magneton ratio	µe/µB	−1.001159652 181 28(18)
to nuclear magneton ratio	µe/µN	−1838.281971 88(11)
electron magnetic moment anomaly |µe|/µB −1	ae	1.159652 18128(18)× 10−3
electron g-factor −2(1+ ae)	ge	−2.002319304 362 56(35)
electron-proton magnetic moment ratio	µe/µp	−658.210687 89(20)
muon mass in u	mµ	0.113428 9259(25)	u
energy equivalent in MeV	mµ c 2	105.6583755(23)	MeV
muon-electron mass ratio	mµ /me	206.7682830(46)
muon magnetic moment	µµ	−4.49044830(10)× 10−26	J T−1
to Bohr magneton ratio	µµ /µB	−4.84197047(11)× 10−3
to nuclear magneton ratio	µµ /µN	−8.89059703(20)
muon magnetic moment anomaly µµ |/(eħ/2mµ)-1	aµ	1.165920 89(63)× 10−3
muon g-factor −2(1+ aµ )	gµ	−2.002331 8418(13)
muon-proton magnetic moment ratio	µµ /µp	−3.183345 142(71)
proton mass	mp	1.672621 923 69(51)× 10−27	kg
in u		1.007276 466 621(53)	u
energy equivalent in MeV	mpc 2	938.272 08816(29)	MeV
proton-electron mass ratio	mp/me	1836.152 67343(11)
proton magnetic moment	µp	1.410606 797 36(60)× 10−26	J T-1
to nuclear magneton ratio	µp/µN	2.792847 344 63(82)
proton magnetic shielding correction 1−µ'p/µp	σ'p	2.5689(11)× 10−5
(H2O, sphere, 25 °C)
proton gyromagnetic ratio 2µp/ħ	γp	2.675221 8744(11)× 108	s−1 T−1
		42.577478 518(18)	MHz T-1
shielded proton gyromagnetic ratio 2µ ′ p/ħ	γ'p	2.675153 151(29)× 108	s −1 T−1
(H2O, sphere, 25 °C)
neutron mass in u	mn	1.008664 915 95(49)	u
energy equivalent in MeV	mnc 2	939.565 42052(54)	MeV
neutron-proton mass ratio	mn/mp	1.001378 419 31(49)
neutron magnetic moment	µn	−9.6623651(23)× 10−27	J T-1
to nuclear magneton ratio	µn/µN	−1.913042 73(45)
deuteron mass in u	md	2.013553 212 745(40)	u
energy equivalent in MeV	mdc 2	1875.612 94257(57)	MeV
deuteron-proton mass ratio	md/mp	1.999007 501 39(11)
deuteron magnetic moment	µd	4.330735 094(11)× 10−27	J T-1
to nuclear magneton ratio	µd/µN	0.857438 2338(22)
helion (3He nucleus) mass in u	mh	3.014932 247 175(97)	u
energy equivalent in MeV	mhc 2	2808.391 60743(85)	MeV
shielded helion magnetic moment	μ'h	−1.074553 090(13)× 10−26	J T−1
(gas, sphere, 25 °C)
to Bohr magneton ratio	µ'h/µB	−1.158671 471(14)× 10−3
to nuclear magneton ratio	µ'h/µN	−2.127497 719(25)
alpha particle mass in u	mα	4.001506 179 127(63)	u
energy equivalent in MeV	mα c 2	3727.379 4066(11)	MeV
Boltzmann constant	K	1.380649 × 10−23 (exact)	J K−1
Avogadro constant	NA	6.022140 76 × 1023 (exact)	mol−1
atomic mass constant C) = 1/12 m(12 C = 1 u)	mu	1.660539 066 60(50)× 10−27	kg
energy equivalent in MeV	muc 2	931.494 10242(28)	MeV
Faraday constant NAe	F	96485.332 12 . . .	C mol−1
molar gas constant NAk	R	8.314462 618 . . .	J mol−1 K−1
in eV K−1		8.617333 262 . . . × 10−5	eV K−1
molar volume of ideal gas RT/p	Vm	22.413969 54 . . . × 10−3	m3 mol−1
(T =273.15 K, p =101.325 kPa)
Stefan-Boltzmann constant π 2k4/60ħ3c2	σ	5.670374 419 . . . × 10−8	Wm-2K-4
first radiation constant 2πhc 2	c1	3.741771 852 . . . × 10−16	[W m 2]
second radiation constant hc/k	c2	1.438776 877 . . . × 10−2	[m K]
Wien displacement law constant
b = λmaxT = c2/4.965114 231...	b	2.897771 955 . . . × 10−3	[m K]
Cu x unit: λ(Cu Kα1)/1537.400	xu(Cu Kα1)	1.002076 97(28)× 10−13	m
Mo x unit: λ(Mo Kα1)/707.831	xu(Mo Kα1)	1.002099 52(53)× 10−13	m
Energy Equivalents
[1 m −1]c = 299792 458 Hz
[1 m −1]hc/k = 1.438776 877. . . × 10−2 K
[1 m −1]hc = 1.239841 984. . . × 10−6 eV
[1 m −1]h/c = 1.331025 05010(40)× 10−15 u
(1 Hz)/c = 3.335640 951. . . × 10−9 [m −1]
(1 Hz)h/k = 4.799243 073. . . × 10−11 K
(1 Hz)h = 4.135667 696. . . × 10−15 eV
(1 K)k/hc = 69.503480 04. . . [m −1]
(1 K)k/h = 2.083661 912. . . × 1010 Hz
(1 K)k = 8.617333 262. . . × 10−5 eV
(1 J) = 6.241509 074. . . × 1018 eV
(1 eV) = 1.602176 634 × 10−19 J
(1 eV)/hc = 8.065543 937. . . × 105 [m −1]
(1 eV)/h = 2.417989 242. . . × 1014 Hz
(1 eV)/k = 1.160451 812. . . × 104 K
(1 eV)/c2 = 1.073544 10233(32)× 10−9 u
(1 kg) = 6.022140 7621(18)× 1026 u
(1 u) = 1.660539 06660(50)× 10−27 kg
(1 u)c/h = 7.513006 6104(23)× 1014 [m −1]
(1 u)c 2 = 9.314941 0242(28)× 108 eV

Source

Physical Measurement Laoratory of NIST, May 2024