Resolution 3 of the 13th CGPM

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,


  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.

reference The reader should note that the official version of this Resolution is the French text


  • 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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