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ISO 31

Superseded standard on quantities and units

Wikipedia contributorsAdapted for Fathomly · View authors
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Source updated August 20, 2026

ISO 31 (Quantities and units, International Organization for Standardization, 1992) is a superseded international standard concerning physical quantities, units of measurement, their interrelationships and their presentation. It was revised and replaced by ISO/IEC 80000.

01Parts

The standard comes in 14 parts:

A second international standard on quantities and units is IEC 60027. The ISO 31 and IEC 60027 Standards were revised by the two standardization organizations in collaboration (, ) 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.

02Coined words

ISO 31-0 introduced several new words into the English language that are direct spelling-calques from the French. Some of these words have been used in scientific literature.

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
Watch videos about ISO 31Explainers and documentaries on YouTube (opens in a new tab)

Sources and credits

This article is adapted from the Wikipedia article “ISO 31”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.

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Related topics

International System of Units

The International System of Units, internationally known by the abbreviation SI, is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official status in nearly every country in the world, employed in science, technology, industry, and everyday commerce.

International Bureau of Weights and Measures

The International Bureau of Weights and Measures is an intergovernmental organisation (IGO), through which its 67 member-states act on measurement standards in areas including chemistry, ionising radiation, physical metrology, as well as the International System of Units (SI) and Coordinated Universal Time (UTC). It is headquartered in the Pavillon de Breteuil in Saint-Cloud, near Paris, France.

ISO 31-0

ISO 31-0 is the introductory part of international standard ISO 31 on quantities and units. It provides guidelines for using physical quantities, quantity and unit symbols, and coherent unit systems, especially the SI. It was intended for use in all fields of science and technology and is augmented by more specialized conventions defined in other parts of the ISO 31 standard.