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 on 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 us this handy reference table.

Commonly Used Physical Constants

ConstantSymbolValue
acceleration due to gravityg9.8 m s-2
atomic mass unitamu, mu or u1.66 x10-27 kg
Avogadro's NumberN6.022 x 1023 mol-1
Bohr radiusa00.529 x 10-10 m
Boltzmann constantk1.38 x 10-23 J K-1
electron charge to mass ratio-e/me-1.7588 x 1011 C kg-1
electron classical radiusre2.818 x 10-15 m
electron mass energy (J)mec28.187 x 10-14 J
electron mass energy (MeV)mec20.511 MeV
electron rest massme9.109 x 10-31 kg
Faraday constantF9.649 x 104 C mol-1
fine-structure constantα7.297 x 10-3
gas constantR8.314 J mol-1 K-1
gravitational constantG6.67 x 10-11 Nm2kg-2
neutron mass energy (J)mnc21.505 x 10-10 J
neutron mass energy (MeV)mnc2939.565 MeV
neutron rest massmn1.675 x 10-27 kg
neutron-electron mass ratiomn/me1838.68
neutron-proton mass ratiomn/mp1.0014
permeability of a vacuumμ04π x 10-7 N A-2
permittivity of a vacuumε08.854 x 10-12 F m-1
Planck constanth6.626 x 10-34 J s
proton mass energy (J)mpc21.503 x 10-10 J
proton mass energy (MeV)mpc2938.272 MeV
proton rest massmp1.6726 x 10-27 kg
proton-electron mass ratiomp/me1836.15
Rydberg constantr1.0974 x 107 m-1
speed of light in vacuumC2.9979 x 108 m/s