Outline of the metric system

The following outline is provided as an overview of and topical guide to the metric system:

Metric system various loosely related systems of measurement that trace their origin to the decimal system of measurement introduced in France during the French Revolution.

Nature of the metric system

The metric system can be described as all of the following:

  • System set of interacting or interdependent components forming an integrated whole.
    • System of measurement set of units which can be used to specify anything which can be measured. Historically, systems of measurement were initially defined and regulated to support trade and internal commerce. Units were arbitrarily defined by fiat (see statutory law) by the ruling entities and were not necessarily well inter-related or self-consistent. When later analyzed and scientifically, some quantities were designated as base units, meaning all other needed units of measure could be derived from them.

Essence of the metric system

Underlying philosophy

Discussions of the underlying philosophy of the metric system (and other systems of measure) include:

Metric units of measure

Articles that exist for many units of measure that are related to various flavours of the metric system are catalogued below. The codes in the various columns have the following meanings:

  • A – Base unit
  • B – Multiple or submultiple of a base unit
  • C – Derived metric unit with a special name
  • D – Derived coherent metric unit that has no special name
  • E – Non-coherent unit explicitly permitted for use within the metric system (SI only)
  • F – Unit of measure that has an association with the metric system
  • X – No specified relationship (Other metric only)
NameQuantitySI unitcgs unitOther metricNon-metric
abampereelectric currentC
abcoulombelectric chargeC
abohmelectrical resistanceC
abvoltpotential differenceC
ampereelectric currentA
ampere-metermagnetic pole strengthD
astronomical unitlengthE
becquerelradioactive activityC
candela per square metreluminanceD
candelaluminous intensityA
degree CelsiustemperatureC
coulombelectric chargeC
cubic centimetrevolumeDD
cubic metre per secondvolumetric flow rateDD
cubic metrevolumeDD
curieradioactive activityC
degree of arcangleE
gaussmagnetic flux densityC
grayabsorbed doseC
joule per moleenergy per amount of substanceD
joule-secondangular momentumD
katalcatalytic activityC
kilogram per cubic metredensityDD
kilometres per hourvelocityX
lumenluminous fluxC
lumen secondluminous energyD
lux secondluminous exposureD
maxwellmagnetic fluxC
metre per second squaredaccelerationDD
metre squared per secondangular momentumDD
minute of arcangleE
moleamount of substanceA
newton metretorqueD
newton-secondimpulse or momentumD
oerstedmagnetic field strengthC
ohmelectric resistanceC
poisedynamic viscosityC
radian per secondangular frequencyD
rayleighphoton fluxX
roentgenkerma of X-rays and gamma raysD
roentgen equivalent manradiation dose equivalentD
siemenselectric conductanceC
sievertradiation dose equivalentC
square kilometreareaDD
square metreareaDD
statcoulombelectric chargeC
statvoltpotential differenceC
steradiansolid angleC
stokeskinematic viscosityC
teslamagnetic field strengthC
voltpotential differenceC
watt secondenergyD
webermagnetic fluxC

History of the metric system

History of the metric system the metric system developed from a decimal system of measurement adopted by France after the French Revolution.

Chronological history of the metric system

Principal dates in the development of the metric system include:[1]

  • 1792 – Initiation of a decimal system of measurement by the French Revolutionary Government
  • 1799 – The Metre des archives and kilogram des archives become the standards for the metric system.
  • 1861 – Concept of unit coherence introduced by Maxwell – the base units were the centimetre, gram and second.
  • 1875 – Under the Convention of the metre, a new body the General Conference on Weights and Measures (CGPM) was set up and given responsibility for the new international prototype kilogram and international prototype metre which replaced the old French copies as the definitive prototype metre and kilogram.
  • 1881 – International Electric Congress agrees on standards for electrical units (formalised in 1893)
  • 1921 – Convention of the metre extended to cover all physical units of measure
  • 1960 – The CGPM published the metric system under the name "International System of Units" (SI) a coherent system of units based on the kilogram, metre, second, ampere and kelvin.

History of metrication

History of metrication metrication is the process by which legacy, national-specific systems of measurement were replaced by the metric system.

Historical metric system variants

Four variants of the metric system that predate the introduction of SI (1960) are described in varying levels of detail:

Between 1812 and 1839 France used a quasi-metric system:

History of metric units

Politics of the metric system

Prior to 1875 the metric system was controlled by the French Government. In that year, seventeen nations signed the Metre Convention and the management and administration of the system passed into international control.

Both the European Union and the International Organization for Standardization have issued directives/recommendations to harmonise the use of units of measure. These documents endorse the use of SI for most purposes.

Future of the metric system

Metric system organizations

Metric system publications

Persons influential in the metric system

See also


  1. International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), pp. 108–110, ISBN 92-822-2213-6, archived (PDF) from the original on 2017-08-14
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