ISO 31

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International Standard ISO 31 (Quantities and units, International Organization for Standardization, 1992) was the most widely respected[weasel words] style guide for the use of physical quantities and units of measurement, and formulas involving them, in scientific and educational documents worldwide.[citation needed] In most countries, the notations used in mathematics and science textbooks at schools and universities follow closely the guidelines given by ISO 31.[citation needed] It is now superseded by the harmonized ISO/IEC 80000 standard.[citation needed]


The standard comes in 14 parts:

A second international standard on quantities and units was IEC 60027[citation needed]. The ISO 31 and IEC 60027 Standards were revised by the two standardization organizations in collaboration ([1], [2]) to integrate both standards into a joint standard ISO/IEC 80000 - Quantities and Units in which the quantities and equations used with SI are to be referred as the International System of Quantities (ISQ). ISO/IEC 80000 supersedes both ISO 31 and part of IEC 60027.

Coined words

ISO 31-0 introduced several new words into the English language that are direct spelling-calques from the French.[1] The intention was that these words be used in scientific papers for the sake of convenience and clarity.

New phrase Existing phrase Technical meaning
massic <quantity> specific <quantity> a quantity divided by its associated mass
volumic <quantity> [volumic] <quantity> density a quantity divided by its associated volume
areic <quantity> surface <quantity> density a quantity divided by its associated area
lineic <quantity> linear <quantity> density a quantity divided by its associated length

Related national standards

  • Canada: CAN/CSA-Z234-1-89 Canadian Metric Practice Guide (covers some aspects of ISO 31-0, but is not a comprehensive list of physical quantities comparable to ISO 31)
  • United States: There are several national SI guidance documents, such as NIST SP 811, NIST SP 330, NIST SP 814, IEEE/ASTM SI 10, SAE J916. These cover many aspects of the ISO 31-0 standard, but lack the comprehensive list of quantities and units defined in the remaining parts of ISO 31.

See also

  • SI – the international system of units
  • BIPM – publishes freely available information on SI units [3], which overlaps with some of the material covered in ISO 31-0
  • IUPAP – much of the material in ISO 31 comes originally from Document IUPAP-25 of the Commission for Symbols, Units and Nomenclature (SUN Commission) [4] of the International Union of Pure and Applied Physics
  • IUPAC – some of the material in ISO 31 originates from the Interdivisional Committee on Terminology, Nomenclature and Symbols [5] of the International Union of Pure and Applied Chemistry
  • Quantities, Units and Symbols in Physical Chemistry – this IUPAC "Green Book" covers many ISO 31 definitions
  • IEC 60027 Letter symbols to be used in electrical technology
  • ISO 1000 SI Units and Recommendations for the use of their multiples and of certain other units (bundled with ISO 31 as the ISO Standards Handbook – Quantities and units)


  1. NIST SP811(§8.9)


External links