Recommendation 1 of the 17th CCQM (2011)

On the need for further guidance on the expression of measurement results based on counting (enumeration)

The Consultative Committee for Amount of Substance – Metrology in Chemistry (CCQM),


  • the increasing importance of methods of measurement based on counting (enumeration) notably in the biosciences and biotechnology,
  • that units of measurement for counting (enumeration) are not currently dealt with in the SI brochure other than by mentioning the SI unit one,
  • that the International Union of Pure and Applied Chemistry (IUPAC) and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommend the use of the unit one for number of entities,
  • that results of measurements of number of entities are currently expressed in various local units,


  • that the SI brochure should now be extended to provide guidance on units for the expression of measurement results based on counting (enumeration).

DOI : 10.59161/CCQM2011REC1E

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

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