List of international units
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This list of international units is subsidiary to the list of units article and lists widely used modern units in a form of sortable table.
Unit system | Domain | Derivation | Unit name | Unit symbol | Dimension symbol | Quantity name | Definition | In SI base units | In other SI units |
---|---|---|---|---|---|---|---|---|---|
SI | Physics | Basic | second [n 1] |
s | T | time | The duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom. | s | |
SI | Physics | Basic | metre | m | L | length | The distance travelled by light in vacuum in 1/299792458 second. | m | |
SI | Physics | Basic | kilogram [n 2] |
kg | M | mass | The kilogram is defined by setting the Planck constant h exactly to 6.62607015×10−34 J⋅s (J = kg⋅m2⋅s−2), given the definitions of the metre and the second.[1] | kg | |
SI | Physics | Basic | ampere | A | I | electric current | The flow of exactly 1/1.602176634×10−19 times the elementary charge e per second. Equalling approximately 6.2415090744×1018 elementary charges per second. | A | |
SI | Physics | Basic | kelvin | K | Θ | thermodynamic temperature |
The kelvin is defined by setting the fixed numerical value of the Boltzmann constant k to 1.380649×10−23 J⋅K−1, (J = kg⋅m2⋅s−2), given the definition of the kilogram, the metre, and the second. | K | |
SI | Physics | Basic | mole | mol | N | amount of substance |
The amount of substance of exactly 6.02214076×1023 elementary entities.[n 3] This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol−1. | mol | |
SI | Physics | Basic | candela | cd | J | luminous intensity |
The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 5.4×1014 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. | cd | |
SI | Physics | Relational | radian[n 4] | rad | plane angle | m/m | 1 | ||
SI | Physics | Relational | steradian | sr | solid angle | m2/m2 | 1 | ||
SI | Physics | Relational | hertz | Hz | frequency | s−1 | |||
SI | Physics | Relational | newton | N | force | kg⋅m⋅s−2 | |||
SI | Physics | Relational | pascal | Pa | pressure | kg⋅m−1⋅s−2 | N/m2 | ||
SI | Physics | Relational | joule | J | energy, work, heat | kg⋅m2⋅s−2 | N⋅m = Pa⋅m3 | ||
SI | Physics | Relational | watt | W | power, radiant flux | kg⋅m2⋅s−3 | J/s | ||
SI | Physics | Relational | coulomb | C | electric charge | s⋅A | |||
SI | Physics | Relational | volt | V | electrical potential difference (voltage), emf | kg⋅m2⋅s−3⋅A−1 | W/A = J/C | ||
SI | Physics | Relational | farad | F | capacitance | kg−1⋅m−2⋅s4⋅A2 | C/V | ||
SI | Physics | Relational | ohm | Ω | resistance, impedance, reactance | kg⋅m2⋅s−3⋅A−2 | V/A | ||
SI | Physics | Relational | siemens | S | electrical conductance | kg−1⋅m−2⋅s3⋅A2 | Ω−1 | ||
SI | Physics | Relational | weber | Wb | magnetic flux | kg⋅m2⋅s−2⋅A−1 | V⋅s | ||
SI | Physics | Relational | tesla | T | magnetic flux density | kg⋅s−2⋅A−1 | Wb/m2 | ||
SI | Physics | Relational | henry | H | inductance | kg⋅m2⋅s−2⋅A−2 | Wb/A | ||
SI | Physics | Relational | degree Celsius | °C | temperature relative to 273.15 K | K | |||
SI | Physics | Relational | lumen | lm | luminous flux | cd⋅sr | |||
SI | Physics | Relational | lux | lx | illuminance | cd⋅sr⋅m−2 | lm/m2 | ||
SI | Physics | Relational | becquerel | Bq | radioactivity (decays per unit time) | s−1 | |||
SI | Physics | Relational | gray | Gy | absorbed dose (of ionising radiation) | m2⋅s−2 | J/kg | ||
SI | Physics | Relational | sievert | Sv | equivalent dose (of ionising radiation) | m2⋅s−2 | J/kg | ||
SI | Physics | Relational | katal | kat | catalytic activity | mol⋅s−1 | |||
SI | Physics | Dimensional | square metre | m2 | A | area | |||
SI | Physics | Dimensional | cubic metre | m3 | V | volume | |||
SI | Physics | Relational | metre per second | m/s | v | speed, velocity | |||
SI | Physics | Relational | metre per second squared | m/s2 | a | acceleration | |||
SI | Physics | Relational | reciprocal metre | m−1 | σ, ṽ or in optics V, 1/f | wavenumber, vergence (optics) | |||
SI | Physics | Relational | kilogram per cubic metre | kg/m3 | ρ | density | |||
SI | Physics | Relational | kilogram per square metre | m−1 | ρA | surface density | |||
SI | Physics | Relational | cubic metre per kilogram | m3/kg | v | specific volume | |||
SI | Physics | Relational | ampere per square metre | A/m2 | j | current density | |||
SI | Physics | Relational | ampere per metre | A/m | H | magnetic field strength | |||
SI | Physics | Relational | mole per cubic metre | mol/m3 | c | concentration | |||
SI | Physics | Relational | kilogram per cubic metre | kg/m3 | ρ, γ | mass concentration | |||
SI | Physics | Relational | candela per square metre | cd/m2 | Lv | luminance | |||
? | Economics | Relational | velocity of money | ||||||
? | Economics | Relational | gross margin |
Notes
[edit]- ^ Within the context of the SI, the second is the coherent base unit of time, and is used in the definitions of derived units. The name "second" historically arose as being the 2nd-level sexagesimal division (1⁄602) of some quantity, the hour in this case, which the SI classifies as an "accepted" unit along with its first-level sexagesimal division the minute.
- ^ Despite the prefix "kilo-", the kilogram is the coherent base unit of mass, and is used in the definitions of derived units. Nonetheless, prefixes for the unit of mass are determined as if the gram were the base unit.
- ^ When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
- ^ The radian and steradian are defined as dimensionless derived units.
- ^ Materese, Robin (16 November 2018). "Historic Vote Ties Kilogram and Other Units to Natural Constants". NIST. Retrieved 16 November 2018.