Triad Separators in Metric Measurement


It is recommended that, to facilitate the reading of numbers with many digits in metric measurement, the Branch continue its practice of introducing a separator between groups of three digits, counting to the left and right from the decimal marker. Such a triad separator should be a small space (except in the "optional" case set out below), rather than the comma used in imperial measurement.

Such a triad separator is optional with a four-digit number. For example, one may use either 1 234 or 1234. The space, however, should be used when the four-digit number appears in a column with other numbers having five or more digits. Whichever manner is opted for, the document (and any amendments) should remain internally consistent.


  • Write: 32 453.246 072 5 or 32 453.246 0725
  • Write: 1245 (1 245 is optional)
  • Write: 3.1416 (3.141 6 is optional), but write 3.141 59.

Since monetary units are not part of the international system of units, the rule cited above is not applicable, and the comma is used as the triad separator ($10,000.00).


Despite the fact that several media sources (see www.cbc.ca) appear to have opted for a mixed usage in metric triad separators (combining the comma of imperial measurement with the units of metric measurement), federal legislation should adhere to the uniformity of the international system of units (SI usage). Further information respecting metric usage may be found in the Federal Regulations Manual.


  • Metric Practice Guide, National Standard of Canada CAN/CSA-Z1234.1-00
  • The Canadian Style, Public Works and Government Services, Translation Bureau, 1997
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