Quantities and units

ISO has published the International Standard ISO 80000, Quantities and units (14 parts).

SI denotes Système International d'Unités, i.e. the International System of Units. The letters SI are used in all languages to denote this system.

The SI is a system of units adopted by the highest international authority on units, i.e. the General Conference on Weights and Measures (Conférence Général des Poids et Mesures, CGPM). It is founded on older metric systems, and has been designed to be suitable for use in every context - customary, technical, and scientific.

The SI is built in such a way that only one unit is used for each kind of quantity. This makes the total number of units less and the system becomes easier to learn and to use.

The structure of the system also makes calculations easier. The benefits of the SI are most evident when its rules are applied consistently.

ISO has published the SI Guide, a small manual for the use of the SI units. Information on this publication is available through the related Press release.