Non-SI units mentioned in the SI
From Infogalactic: the planetary knowledge core
This is a list of units that are not defined as part of the International System of Units (SI), but are otherwise mentioned in the SI,[1][2] because either the General Conference on Weights and Measures (CGPM) accepts their use as being multiples or submultiples of SI-units, they have important contemporary application worldwide, or are otherwise commonly encountered worldwide.
Contents
Units officially accepted for use with the SI
Name | Symbol | Quantity | Equivalent SI unit |
---|---|---|---|
Widely used units expected to be used indefinitely | |||
minute | min | time (SI unit multiple) | 1 min = 60 s |
hour | h | time (SI unit multiple) | 1 h = 60 min = 3600 s |
day | d | time (SI unit multiple) | 1 d = 24 h = 1440 min = 86400 s |
degree | ° | plane angle (dimensionless unit) | 1° = (π / 180) rad |
minute | ′ | plane angle (dimensionless unit) | 1′ = (1 / 60)° = (π / 10800) rad |
second | ″ | plane angle (dimensionless unit) | 1″ = (1 / 60)′ = (1 / 3600)° = (π / 648000) rad |
hectare | ha | area (decimal unit multiple) | 1 ha = 100 a = 10000 m2 = 1 hm2 |
litre | l or L | volume (decimal unit multiple) | 1 L = 1 dm3 = 0.001 m3 = 1000 cm3 |
tonne | t | mass (decimal unit multiple) | 1 t = 103 kg = 1 Mg |
astronomical unit | au or AU[1][3] | length | 1 AU = 1.495978707×1011 m (exact) |
Logarithmic units | |||
neper | Np | level of a field quantity | 1 Np = 1[4] |
level of a power quantity | 1 Np = 1[5] | ||
bel | B | level of a field quantity | 1 B = ln(10)/2 Np = ln(10)/2[6] |
level of a power quantity | |||
decibel | dB | level of a field quantity | 1 dB = 0.1 B [7] |
level of a power quantity | |||
Units with experimentally determined values | |||
electronvolt | eV | energy | 1 eV = 1.60217653(14)×10−19 J |
unified atomic mass unit dalton |
u Da |
mass | 1 u = 1 Da = 1.66053886(28)×10−27 kg |
Natural units (n.u.) | |||
n.u. of speed (speed of light in vacuum) | c0 | speed | 299792458 m/s (exact)[8] |
n.u. of action (reduced Planck constant) | ħ | action | 1.05457168(18)×10−34 J·s |
n.u. of mass (electron mass) | me | mass | 9.1093826(16)×10−31 kg |
n.u. of time | ħ / mec02 | time | 1.2880886677(86)×10−21 s |
Atomic units (a.u.) | |||
a.u. of charge (elementary charge) | e | electric charge | 1.60217653(14)×10−19 C |
a.u. of mass (electron mass) | me | mass | 9.1093826(16)×10−31 kg |
a.u. of action (reduced Planck constant) | ħ | action | 1.05457168(18)×10−34 J·s |
a.u. of length, bohr (Bohr radius) | a0 | length | 0.5291772108(18)×10−10 m |
a.u. of energy, hartree (Hartree energy) | Eh | energy | 4.35974417(75)×10−18 J |
a.u. of time | ħ / Eh | time | 2.418884326505(16)×10−17 s |
Common units not officially sanctioned
Name | Symbol | Quantity | Equivalent SI unit |
---|---|---|---|
ångström, angstrom | Å | length | 1 Å = 0.1 nm = 10−10 m = 100 pm |
are | a | area | 1 a = 1 dam2 = 100 m2 |
barn | b | area | 1 b = 10−28 m2 |
bar | bar | pressure | 1 bar = 105 Pa |
millibar | mbar | pressure | 1 mbar = 1 hPa = 100 Pa |
atmosphere | atm | pressure | 1 atm = 1013.25 mbar = 1013.25 hPa = 101325 Pa exactly (commonly used in atmospheric meteorology, in oceanography and for pressures within liquids, or in the industry for pressures within containers of liquefied gas) |
dyne per square centimetre (barye) | Ba | pressure | 1 Ba = 0.1 Pa = 0.1 N/m2 = 100 g·cm−1·s−2 |
millimetre of mercury | mmHg | pressure | 1 mmHg = 133.322387415 Pa at 0 °C = 133.322387415 N/m2 at 0 °C = 133.322387415 kg·cm−1·s−2 at 0 °C |
torr | Torr | pressure | 1 Torr = 1/760 atm = 133.322368421... Pa = 133.322368421... N/m2 = 133.322368421... kg·cm−1·s−2 |
See also
- Gal (unit)
- International System of Quantities
- International System of Units (SI)
- International Vocabulary of Metrology
- Metric prefix
- SI base unit
- SI derived unit
References
- ↑ 1.0 1.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ LF = ln(F / F0) Np
- ↑ LP = 1⁄2 ln(P / P0) Np
- ↑ LF = 2 log10(F / F0) B
- ↑ LP = log10(P / P0) B
- ↑ In this case it is not the speed of light, but the length of the metre that is obtained by experiment