Table of Physical Constants

Commonly Used Constants

It's good to know the speed of light, one of the physical constants, since it is used in many calculations.
It's good to know the speed of light, one of the physical constants, since it is used in many calculations. Nick Koudis/Getty Images

Need a value for a fundamental physical constant? Typically, these values are learned only in the short term as you are introduced to them and forgotten as soon as the test or task is finished. When they are needed again, constant searching through the textbook is one way to find the information again. A better way would be to use this handy reference table.​

Commonly Used Physical Constants

Constant Symbol Value
acceleration due to gravity g 9.8 m s -2
atomic mass unit amu, m u or u 1.66 x10 -27 kg
Avogadro's Number N 6.022 x 10 23 mol -1
Bohr radius a 0 0.529 x 10 -10 m
Boltzmann constant k 1.38 x 10 -23 J K -1
electron charge to mass ratio -e/m e -1.7588 x 10 11 C kg -1
electron classical radius r e 2.818 x 10 -15 m
electron mass energy (J) m ec 2 8.187 x 10 -14 J
electron mass energy (MeV) m ec 2 0.511 MeV
electron rest mass m e 9.109 x 10 -31 kg
Faraday constant F 9.649 x 10 4 C mol -1
fine-structure constant α 7.297 x 10 -3
gas constant R 8.314 J mol -1 K -1
gravitational constant G 6.67 x 10 -11 Nm 2kg -2
neutron mass energy (J) m nc 2 1.505 x 10 -10 J
neutron mass energy (MeV) m nc 2 939.565 MeV
neutron rest mass m n 1.675 x 10 -27 kg
neutron-electron mass ratio m n/m e 1838.68
neutron-proton mass ratio m n/m p 1.0014
permeability of a vacuum μ 0 4π x 10 -7 N A -2
permittivity of a vacuum ε 0 8.854 x 10 -12 F m -1
Planck constant h 6.626 x 10 -34 J s
proton mass energy (J) m pc 2 1.503 x 10 -10 J
proton mass energy (MeV) m pc 2 938.272 MeV
proton rest mass m p 1.6726 x 10 -27 kg
proton-electron mass ratio m p/m e 1836.15
Rydberg constant r 1.0974 x 10 7 m -1
speed of light in vacuum C 2.9979 x 10 8 m/s
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Your Citation
Helmenstine, Todd. "Table of Physical Constants." ThoughtCo, Aug. 25, 2020, thoughtco.com/table-of-physical-constants-603967. Helmenstine, Todd. (2020, August 25). Table of Physical Constants. Retrieved from https://www.thoughtco.com/table-of-physical-constants-603967 Helmenstine, Todd. "Table of Physical Constants." ThoughtCo. https://www.thoughtco.com/table-of-physical-constants-603967 (accessed April 16, 2021).