SI Units

The international system of units known as the SI units is based on the seven basic units: Mass, Length, Time, Electric current, Temperature, Amount of substance and Luminous intensity.

Basic Units

The basic seven quantities from which other units are derived are tabulated below:

Basic quantityNameSymbol
Masskilogramkg
Lengthmetrem
Timeseconds
Electric currentAmpereA
TemperatureKelvinK
Amount of substancemolemol
Luminous intensitycandelacd

The radian and steradian may also be treated as basic units.

Derived Units

These are multiplications and divisions of the basic units to form derived units. Some of these derived units are listed below along with their derivation in terms of basic units:

Derived quantityNameSymbolBasic Unit Derivation
CapacitancefaradFkg-1m-2s4A2
ChargecoulombCAs
ConductancesiemensSkg-1m-2s3A2
Electromotive ForcevoltVkgm2s-3A-1
EnergyjouleJkgm2s-2
ForcenewtonNkgms-2
FrequencyhertzHzs-1
InductancehenryHkgm2s-2A-2
Magnetic FluxweberWbkgm2s-2A-1
Magnetic Flux DensityteslaTkgs-2A-1
PowerwattWkgm2s-3
PressurepascalPakgm-1s-2
ResistanceohmΩkgm2s-3A-2

Reference

1866 The use of the metric system in the United States was legalized by Congress but was not made obligatory.

See also: Absolute System of Units, Arbitrary Unit, Atomic Unit, Base Unit, CGS Units, Derived Units, Dimensions, Force, MKS System, MKSA System, Unit, Velocity, Volume.

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International Standards Organisation Responsible for the world-wide publication of standards.
National Institute of Standards and Technology USA based organisation.