{
  "url": "https://openlegislation.uk/eu-directive-1980-181/annex/chapter-I/division-1/division-1.1",
  "json_url": "https://openlegislation.uk/eu-directive-1980-181/annex/chapter-I/division-1/division-1.1.json",
  "legislation": "eudr/1980/181",
  "legislation_title": "Council Directive of 20 December 1979 on the approximation of the laws of the Member States relating to units of measurement and on the repeal of Directive 71/354/EEC (80/181/EEC)",
  "legislation_url": "https://openlegislation.uk/eu-directive-1980-181",
  "path": "annex/chapter/I/division/1/division/1.1",
  "kind": "division",
  "number": "1.1",
  "heading": "SI base units",
  "text": "Quantity\nUnit\nName\nSymbol\nTime\nsecond\ns\nLength\nmetre\nm\nMass\nkilogram\nkg\nElectric current\nampere\nA\nThermodynamic temperature\nkelvin\nK\nAmount of substance\nmole\nmol\nLuminous intensity\ncandela\ncd\nDefinitions of SI base units:\nUnit of time\nThe second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency Δ ν Cs , the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s –1 .\nUnit of length\nThe metre, symbol m, is the SI unit of length. It is defined by taking the fixed numerical value of the speed of light in vacuum c to be 299 792 458 when expressed in the unit m/s, where the second is defined in terms of Δ ν Cs .\nUnit of mass\nThe kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6,626 070 15 × 10 –34 when expressed in the unit J s, which is equal to kg m 2 s –1 , where the metre and the second are defined in terms of c and Δ ν Cs .\nUnit of electric current\nThe ampere, symbol A, is the SI unit of electric current. It is defined by taking the fixed numerical value of the elementary charge e to be 1,602 176 634 × 10 –19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of Δ ν Cs .\nUnit of thermodynamic temperature\nThe kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by taking the fixed numerical value of the Boltzmann constant k to be 1,380 649 × 10 –23 when expressed in the unit J K –1 , which is equal to kg m 2 s –2 K –1 , where the kilogram, metre and second are defined in terms of h , c and Δ ν Cs .\nUnit of amount of substance\nThe mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6,022 140 76 × 10 23 elementary entities. This number is the fixed numerical value of the Avogadro constant, N A, when expressed in the unit mol –1 and is called the Avogadro number.\nThe amount of substance, symbol n , of a system is a measure of the number of specified elementary entities. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles.\nUnit of luminous intensity\nThe candela, symbol cd, is the SI unit of luminous intensity in a given direction. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 10 12 Hz, K cd , to be 683 when expressed in the unit lm W –1 , which is equal to cd sr W –1 , or cd sr kg –1 m –2 s 3 , where the kilogram, metre and second are defined in terms of h , c and Δ ν Cs .",
  "extent": "E+W+S+N.I.",
  "status": null,
  "version": "current",
  "annotations": [
    {
      "type": "F",
      "label": "F1",
      "text": "Substituted by Commission Directive (EU) 2019/1258 of 23 July 2019 amending, for the purpose of its adaptation to technical progress, the Annex to Council Directive 80/181/EEC as regards the definitions of SI base units (Text with EEA relevance)."
    },
    {
      "type": "X",
      "label": "X1",
      "text": "Substituted by Corrigendum to Council Directive 80/181/EEC of 20 December 1979 on the aproximation of the laws of the Member States relating to units of measurement and on the repeal of Directive 71/354/EEC (Official Journal of the European Communities No L 39 of 15 February 1980)."
    }
  ],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/eudr/1980/181/annex/chapter/I/division/1/division/1.1",
    "retrieved_at": "2026-11-01T15:23:40.868248+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}