Resolution 3 of the 13th CGPM (1967/68)
SI unit of thermodynamic temperature (kelvin)

The 13th Conférence Générale des Poids et Mesures (CGPM),


  • the names "degree Kelvin" and "degree", the symbols "°K" and "deg" and the rules for their use given in Resolution 7 of the 9th CGPM (1948), in Resolution 12 of the 11th CGPM (1960), and the decision taken by the Comité International des Poids et Mesures in 1962 (PV, 30, 27),
  • that the unit of thermodynamic temperature and the unit of temperature interval are one and the same unit, which ought to be denoted by a single name and a single symbol,
  • decides

    1. the unit of thermodynamic temperature is denoted by the name "kelvin" and its symbol is "K";
    2. the same name and the same symbol are used to express a temperature interval;
    3. a temperature interval may also be expressed in degrees Celsius;
    4. the decisions mentioned in the opening paragraph concerning the name of the unit of thermodynamic temperature, its symbol and the designation of the unit to express an interval or a difference of temperatures are abrogated, but the usages which derive from these decisions remain permissible for the time being.

    Comptes rendus de la 13e CGPM (1967/68), 1969, 104
    Metrologia, null, 4, 1, 41-45


  • At its 1980 meeting, the CIPM approved the report of the 7th meeting of the CCU, which requested that the use of the symbols "°K" and "deg" no longer be permitted.
  • See Recommendation 2 (CI-2005) of the CIPM on the isotopic composition of water entering in the definition of the kelvin.

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