# Table of Physical Constants

Physical Constants |
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Quantity or phenomenon |
Symbol |
SI unit value |
Alternate unit value |

astronomical unit | AU | 1.4959787 x 10^{11}meters |
1.4959787 x 10^{8}kilometers |

atomic mass unit | amu | 1.67377 x 10^{-27}kilogram |
1.67377 x 10^{-24}gram |

Avogadro constant | N, L |
6.022169 x 10^{23} |
6.022169 x 10^{23} |

Bohr magneton | µ_{B} |
9.274 x 10^{-24}joule per tesla |
9.274 x 10^{-28}joule per gauss |

Bohr radius | a_{o} |
5.29177 x 10^{-11}meter |
5.29177 x 10^{-9}centimeter |

Boltzmann's constant | k |
1.3807 x 10^{-23}joule per kelvin |
1.3807 x 10^{-16}erg per kelvin |

characteristic impedance of free space |
Z_{o} |
377 ohms |
-- |

Compton wavelength of electron | _{ce} |
2.4263 x 10^{-12}meter |
2.4263 x 10^{-10}centimeter |

Compton wavelength of proton | _{cp} |
1.3214 x 10^{-15}meter |
1.3214 x 10^{-13}centimeter |

Compton wavelength of neutron | _{cn} |
1.3196 x 10^{-15}meter |
1.3196 x 10^{-13}centimeter |

Earth's mass | m_{earth} |
5.974 x 10^{24}kilograms |
5.974 x 10^{27}grams |

Earth's mean orbital speed | v_{earth} |
30 kilometers per second |
18.5 miles per second |

Earth's mean radius | r_{earth} |
6.371 x 10^{6}meters |
6371 kilometers |

electron radius | r_{e} |
2.81794 x 10^{-15}meter |
2.81794 x 10^{-13}centimeter |

electron rest mass | m_{e} |
9.10956 x 10^{-31}kilogram |
9.10956 x 10^{-28}gram |

elementary charge | e |
1.60 x 10^{-19}coulomb |
-- |

Euler's constant | 0.577216 | 0.577216 | |

Faraday constant | F |
9.65 x 10^{4}coulombs per mole |
-- |

fine structure constant | 0.007297 | 0.007297 | |

first radiation constant | c_{1} |
4.9926 x 10^{-24}joule-meter |
4.9926 x 10^{-15}erg-centimeter |

gas constant | R |
8.3145 joules per kelvin per mole |
8.3145 x 10^{7}ergs per kelvin per mole |

gravitational acceleration at Earth's surface |
g |
9.8067 meters per second squared |
980.67 centimeters per second squared |

gravitational constant | G |
6.67 x 10^{-11}newton meter squared per kilogram squared |
-- |

Hartree energy | E_{h} |
4.3597 x 10^{-18}joule |
4.3597 x 10^{-11}erg |

Moon's mass | m_{moon} |
7.348 x 10^{22}kilograms |
7.348 x 10^{25}grams |

Moon's mean radius | r_{moon} |
1.738 x 10^{6}meters |
1738 kilometers |

natural logarithm base | e |
2.718282 | 2.718282 |

neutron radius | r_{n} |
* | * |

neutron rest mass | m_{n} |
1.67492 x 10^{-27}kilogram |
1.67492 x 10^{-24}gram |

nuclear magneton | µ_{n} |
5.051 x 10^{-27}joule per tesla |
5.051 x 10^{-31}joule per gauss |

permeability of free space | µ_{o} |
1.257 x 10^{-6}henry per meter |
1.257 microhenrys per meter |

permittivity of free space | _{o} |
8.85 x 10^{-12}farad per meter |
8.85 picofarads per meter |

pi | 3.14159 | 3.14159 | |

Planck's constant | h |
6.626176 x 10^{-34}joule-second |
6.626176 x 10^{-27}erg-second |

proton radius | r_{p} |
2 x 10^{-16} meter * |
2 x 10^{-14} centimeter * |

proton rest mass | m_{p} |
1.67261 x 10^{-27}kilogram |
1.67261 x 10^{-24}gram |

Rydberg constant | R or R_{H} |
1.097 x 10^{7}per meter |
1.097 x 10^{5}per centimeter |

second radiation constant | c_{2} |
0.014388 meter-kelvin |
1.4388 centimeter-kelvin |

speed of light | c |
2.99792 x 10^{8}meters per second |
2.99792 x 10^{10}centimeters per second |

speed of sound in air | v_{sound} |
331.4 meters per second |
1087 feet per second |

Stefan-Boltzmann constant | 5.67 x 10^{-8}watt per meter squared per kelvin to the fourth |
-- | |

Sun's mass | m_{sun} |
1.989 x 10^{30}kilograms |
1.989 x 10^{33}grams |

Sun's mean radius | r_{sun} |
6.970 x 10^{8}meters |
6.970 x 10^{5}kilometers |

Wien's constant | _{w} |
2.898 x 10^{-3}meter-kelvin |
0.2898 centimeter-kelvin |

All values are approximations, accurate to the number of significant digits shown.

*Value depends on environment.