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
_{e}c
^{2} |
8.187 x 10
^{-14} J |

electron mass energy (MeV) | m
_{e}c
^{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
^{2}kg
^{-2} |

neutron mass energy (J) | m
_{n}c
^{2} |
1.505 x 10
^{-10} J |

neutron mass energy (MeV) | m
_{n}c
^{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
_{p}c
^{2} |
1.503 x 10
^{-10} J |

proton mass energy (MeV) | m
_{p}c
^{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 |