Constants

This page lists various constants used in physics and some useful conversions.

## Contents

* 1 Physical constants
* 2 Useful Conversions
* 2.1 Length
* 2.2 Weight
* 2.3 Pressure
* 2.4 Other
* 3 Prefixes
* 4 References

## Physical constants[edit]

The number in brackets represents the uncertainty in the constant, so that  has an uncertainty of .

Name  | Symbol  | Value  | Meaning  | Used in  | Exact

|
|
|
|
|

Planck's constant |  |  | It relates the frequency of a photon to its energy | Quantum mechanics | Inexact[1]
Speed of light |  |  | This is the speed of light in a vacuum | Most of physics, such as optics and relativity | Exact[2]
Permittivity of free space  |  |  | Related to the strength of an electric field produced by a charge  | Electromagnetism | Exact[3]
Permeability of free space  |  |  | Related to the strength of magnetic fields produced by a current | Electromagnetism | Exact[4]
Elementary charge  |  |  | The magnitude of the electric charge on an electron  | Determines the strength of electric and magnetic fields produced by protons, electrons etc.  | Inexact[5]
Avogadro's number |  |  | The number of constituents in 1 mole of something  | Chemistry, statistical mechanics, thermodynamics | Inexact[6]
Ideal gas constant  |  |  | Relates the pressure, volume, temperature and number of moles of an ideal gas | Thermodynamics | Inexact[7]
Faraday Constant  |  |  | The electric charge on one mole of electrons (Avogadro's number times elementary charge)  | Chemistry, physics | Inexact[8]
Gravitational constant |  |  | Constant related to the strength of Newtonian gravity  | Newtonian gravity | Inexact[9]
Boltzmann constant  |  |  | Thermodynamics |  | Inexact[10]
Reduced Planck's constant  |  |  | Quantum mechanics | It is Planck's constant divided by .  | Inexact[11]
Wien displacement constant  |  |  | Relates the temperature of a black body to the peak in its spectrum  |  | Inexact[12]
Standard acceleration due to gravity |  |  | This is the acceleration of any object near to the earth's surface when gravity is the only force acting (i.e., no air resistance).  | Mechanics | Exact[13]
Proton mass  |  |  | Rest mass of a proton |  | Inexact[14]
Neutron mass  |  |  | Rest mass of a neutron |  | Inexact[15]
Electron mass  |  |  | Rest mass of an electron |  | Inexact[16]

## Useful Conversions[edit]

### Length[edit]

1 metre = 39.37 inches 1 metre = 3.281 feet 1 kilometre = 0.6213 miles

1 mile = 5280 feet 1 mile = 1760 yards

### Weight[edit]

1 kilogram = 35.27 ounce 1 kilogram = 2.205 pounds

### Pressure[edit]

1 atm = 101.1 kPa 1 atm = 760 torr 1 atm = 760 mm Hg

### Other[edit]

Atomic mass unit: 1.00 amu = 1.67 x 10−27 kg

1.000 calorie = 4.184 Joules

Standard Temperature and Pressure (STP): temperature = 273 K and pressure = 1.00 atm

* * *

Relative mass and charge of subatomic particles found in atoms.

Atomic particles  |  Relative Mass  |  Relative Charge

|
|

Proton |  1  |  +1
Neutron |  1  |  0
Electron |  1/1837  |  -1

## Prefixes[edit]

Prefixes in front of a unit indicate that that unit should be multiplied by a multiple of ten, e.g. Giga is 109, so 1 GPa = 109 Pa.

Name  | Symbol  | Power

|
|

Pico  | p  | 10−12
nano  | n  | 10−9
micro  | μ  | 10−6
milli  | m  | 10−3
centi  | c  | 10−2
deci  | d  | 10−1
deca  | da  | 101
hecto  | h  | 102
kilo  | k  | 103
mega  | M  | 106
giga  | G  | 109
tera  | T  | 1012

## References[edit]

1. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?h
2. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?c
3. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?ep0
4. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?mu0
5. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?e
6. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?na
7. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?r
8. ↑ http://ch302.cm.utexas.edu/echem/echem-stoich/echem-stoich-all.php
9. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?bg
10. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?k
11. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?hbar
12. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?bwien
13. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?gn
14. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?mp
15. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?mn
16. ↑ http://physics.nist.gov/cgi-bin/cuu/Value?me