| Quantity |
Symbol |
SI unit value |
Alternate unit value |
| Astronomical unit |
AU |
1.4959787 x 1011
metres |
1.4959787 x 108
kilometres |
| Atomic mass unit |
amu |
1.67377 x 10-27
kilogram |
1.67377 x 10-24
gram |
| Avogadro Constant |
N, L |
6.022169 x 1023 |
6.022169 x 1023 |
| Bohr magneton |
µB |
9.274 x 10-24
joule per tesla |
9.274 x 10-28
joule per gauss |
| Bohr radius |
αo |
5.29177 x 10-11
metre |
5.29177 x 10-9
centimetre |
| 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 |
λce |
2.4263 x 10-12
metre |
2.4263 x 10-10
centimetre |
| Compton wavelength of proton |
λcp |
1.3214 x 10-15
metre |
1.3214 x 10-13
centimetre |
| Compton wavelength of neutron |
λcn |
1.3196 x 10-15
metre |
1.3196 x 10-13
centimetre |
| Earth's mass |
m earth |
5.974 x 1024
kilograms |
5.974 x 1027
grams |
| Earth's mean orbital speed |
v earth |
30
kilometres per second |
18.5
miles per second |
| Earth's mean radius |
r earth |
6.371 x 10-6
metres |
6371
kilometres |
| Electron radius |
re |
2.81794 x 10-15
metre |
2.81794 x 10-13
centimetre |
| electron rest mass |
me |
9.10956 x 10-31
kilogram |
9.10956 x 10-28
gram |
| Elementary charge |
e |
1.60 x 10-19
coulomb |
|
| Euler's constant |
γ |
0.577216 |
0.577216 |
| Faraday constant |
F |
9.65 x 10-4
coulombs per mole |
|
| Fine structure constant |
α |
0.007297 |
0.007297 |
| First radiation constant |
c1 |
4.9926 x 10-24
joule-metre |
4.9926 x 10-15
erg-centimetre |
| Gas constant |
R |
8.3145
joules per kelvin per mole |
8.3145 x 107
ergs per kelvin per mole |
| Gravitational acceleration
at Earth's surface |
g |
9.8067
metres per second squared |
980.67
centimetres per second squared |
| Gravitational constant |
G |
6.67 x 10-11
newton metre squared
per kilogram squared |
|
| Hartree energy |
E h |
4.3597 x 10-18
joule |
4.3597 x 10-11
erg |
| Moon's mass |
mmoon |
7.348 x 1022
kilograms |
7.348 x 1025
grams |
| Moon's mean radius |
rmoon |
1.738 x 106
metres |
1738
kilometres |
| Natural logarithm base |
e |
2.718282 |
2.718282 |
| Neutron radius |
rn |
* |
* |
| Neutron rest mass |
mn |
1.67492 x 10-27
kilogram |
1.67492 x 10-24
gram |
| Nuclear magneton |
µn |
5.051 x 10-27
joule per tesla |
5.051 x 10-31
joule per gauss |
| Permeability of free space |
µo |
1.257 x 10-6
henry per metre |
1.257
microhenrys per metre |
| Permittivity of free space |
εo |
8.85 x 10-12
farad per metre |
8.85
picofarads per metre |
| pi |
π |
3.14159 |
3.14159 |
| Planck's constant |
h |
6.626176 x 10-34
joule-second |
6.626176 x 10-27
erg-second |
| Proton radius |
rp |
2 x 10-16
metre * |
2 x 10-14
centimetre * |
| Proton rest mass |
mp |
1.67261 x 10-27
kilogram |
1.67261 x 10-24
gram |
| Rydberg constant |
R or RH |
1.097 x 107
per metre |
1.097 x 105
per centimetre |
| Second radiation constant |
c2 |
0.014388
metre-kelvin |
1.4388
centimetre-kelvin |
| Speed of light |
c |
2.99792 x 108
metres per second |
2.99792 x 1010
centimetres per second |
| Speed of sound in air |
vsound |
331.4
metres per second |
1087
feet per second |
| Stefan-Boltzmann constant |
α |
5.67 x 10-8
watt per metre squared
per kelvin to the fourth |
|
| Sun's mass |
msun |
1.989 x 1030
kilograms |
1.989 x 1033
grams |
| Sun's mean radius |
rsun |
6.970 x 108
metres |
6.970 x 105
kilometres |
| Wien's constant |
αw |
2.898 x 10-3
metre-kelvin |
0.2898
centimetre-kelvin |