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, mu or u 1.66 x10-27 kg
Avogadro's Number N 6.022 x 1023 mol-1
Bohr radius a0 0.529 x 10-10 m
Boltzmann constant k 1.38 x 10-23 J K-1
electron charge to mass ratio -e/me -1.7588 x 1011 C kg-1
electron classical radius re 2.818 x 10-15 m
electron mass energy (J) mec2 8.187 x 10-14 J
electron mass energy (MeV) mec2 0.511 MeV
electron rest mass me 9.109 x 10-31 kg
Faraday constant F 9.649 x 104 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 Nm2kg-2
neutron mass energy (J) mnc2 1.505 x 10-10 J
neutron mass energy (MeV) mnc2 939.565 MeV
neutron rest mass mn 1.675 x 10-27 kg
neutron-electron mass ratio mn/me 1838.68
neutron-proton mass ratio mn/mp 1.0014
permeability of a vacuum μ0 4π x 10-7 N A-2
permittivity of a vacuum ε0 8.854 x 10-12 F m-1
Planck constant h 6.626 x 10-34 J s
proton mass energy (J) mpc2 1.503 x 10-10 J
proton mass energy (MeV) mpc2 938.272 MeV
proton rest mass mp 1.6726 x 10-27 kg
proton-electron mass ratio mp/me 1836.15
Rydberg constant r 1.0974 x 107 m-1
speed of light in vacuum C 2.9979 x 108 m/s