# Fundamental Physical Constants

Fundamental Physical Constants

Name Symbol Value

Speed of light in vacuum c 2.99792458 * 108 m>s

Magnitude of charge of electron e 1.602176634 * 10-19 C

Gravitational constant G 6.674081312 * 10-11 N # m2>kg2

Planck’s constant h 6.62607015 * 10-34 J # s

Boltzmann constant k 1.380649 * 10-23 J>K

Avogadro’s number NA 6.02214076 * 1023 molecules>mol

Gas constant R = NAK 8.314462618c J>mol # K

Mass of electron me 9.109383561112 * 10-31 kg

Mass of proton mp 1.6726218981212 * 10-27 kg

Mass of neutron mn 1.6749274711212 * 10-27 kg

Magnetic constant m0 1.25663706 * 10-6 Wb>A # m 1approximate2 _ 4p * 10-7 Wb>A # m

Electric constant P0 = 1>m0 c2 8.854187817 * 10-12 C2>N # m2 1approximate2

1>4pP0 8.987551787 * 109 N # m2>C2 1approximate2

Other Useful Constants*

Mechanical equivalent of heat 4.186 J>cal 115            calorie2

Standard atmospheric pressure 1 atm 1.01325 * 105 Pa

Absolute zero 0 K -273.15 C

Electron volt 1 eV 1.60217662091982 * 10-19 J

Atomic mass unit 1 u 1.6605390401202 * 10-27 kg

Electron rest energy me c2 0.51099894611312 MeV

Volume of ideal gas 10     C and 1 atm2 22.4139621132 liter>mol

Acceleration due to gravity (standard) g 9.80665 m>s2

*Source: National Institute of Standards and Technology (https://physics.nist.gov/cuu/Constants/). Numbers in parentheses show the uncertainty in the final digits of the main number; for example, the number 1.6454(21) means 1.6454 { 0.0021. Values shown without uncertainties are exact. The exact values of the magnitude of the charge of the electron, Planck’s constant, the Boltzmann constant, Avogadro’s constant, and the gas constant are from the redefinitions adopted in 2018. As consequences of these redefinitions, the values of the magnetic constant and electric constant now have fractional uncertainties of about 2 * 10-10. As of this writing it was expected that updated values of the magnetic and electric constants, as well as of all other constants with uncertainties, were to be announced in May 2019. These updated values will be available at https://physics.nist.gov/cuu/Constants/