| c | Speed of light in vacuum | 2.998×108m s−1 |
| e | Elementary charge | 1.602×10−19 C |
| mn | Neutron rest mass | 1.675×10−27 kg |
| mp | Proton rest mass | 1.6725×10−27 kg |
| me | Electron rest mass | 9.110×10−31 kg |
| mHe | Helium-4 rest mass | 6.644×10−27 kg |
| h | Planck’s constant | 6.626×10−34 J s |
| H0 | Hubble’s constant | 70 (km/s)/Mpc |
| kB | Boltzmann’s constant | 1.381×10−23 J K−1 |
| b | Wien’s constant | 2.898×10−3 m K |
| G | Gravitational constant | 6.673×10−11 N m2 kg−2 |
| σ | Stefan-Boltzmann constant | 5.670×10−8 J m−2 K−4 s−1 |
| c1 | First Radiation Constant (=2πhc2) | 3.742×10−16 J m2 s−1 |
| c2 | Second Radiation Constant (=hc/k) | 1.439×10−2 m K |
| NA | Avogadro constant | 6.022×1023 mol−1 |
| R | Gas constant | 8.314 J K−1 mol−1 |
| a0 | Bohr radius | 5.292×10−11 m |
| μB | Bohr magneton | 9.274×10−24 J T−1 |
| M⊙ | Solar mass | 1.989×1030 kg |
| R⊙ | Solar radius | 6.96×108 m |
| L⊙ | Solar luminosity | 3.827×1026 J s−1 |
| T⊙ | Solar temperature | 5770 K |
| M⊕ | Earth mass | 5.976×1024 kg |
| R⊕ | Mean Earth radius | 6.371×106 m |
| I⊕ | Earth moment of Inertia | 8.04×1037 kg m2 |
| R☾ | Mean Moon radius | 1.737×106 m |
| M♃ | Mean Jupiter mass | 1.9×1027 kg |
| R♃ | Mean Jupiter radius | 7.1492×107 m |
| a♃ | Mean orbital radius of Jupiter | 5.2 AU |
| a☾ | Mean semimajor axis Moon orbit | 3.84399×108 m |
| 1 light year | | 9.461×1015 m |
| 1 AU | Astronomical Unit | 1.496×1011 m |
| 1 pc | Parsec | 3.086×1016 m |
| 1 year | | 3.156×107 s |
| 1 sidereal day | | 86164 s |
| 1 erg | | 1×10−7 J |
| 1 bar | | 105 N m−2 |