International System of Units (SI)

The International System of Units, commonly abbreviated SI from the French Système International d’Unités, is the modern metric system of measurement established by international agreement. It provides the logical, interconnected framework for measurement that IRES’s own “original” and “common” unit conventions are built on [IRES, Ch. IV, para. 4.4, PDF p. 54, 2018]. See Measurement Units for SI’s base units, prefixes, and how IRES applies them to energy statistics.

Governance and history

SI is established and defined by the General Conference on Weights and Measures (CGPM). It is the result of work begun in 1948 to develop recommendations for a practical system of measurement units suitable for adoption by all signatories to the Convention du Mètre [IRES, Ch. IV, Box 4.1, PDF p. 54, 2018].

In 1954 and 1971, the CGPM adopted as base units the units of seven quantities: length, mass, time, electric current, thermodynamic temperature, luminous intensity and amount of substance. In 1960, the CGPM adopted the name Système International d’Unités — with the international abbreviation SI — for this practical system of units, and laid down rules for prefixes, derived units, and the former supplementary units, thereby establishing a comprehensive specification for units of measurement [IRES, Ch. IV, Box 4.1, PDF p. 54, 2018].

The source cited for this account is the International Bureau of Weights and Measures (BIPM) [IRES, Ch. IV, Box 4.1, PDF p. 54, 2018]. Both the CGPM and the BIPM are SI’s custodian bodies — CGPM as the diplomatic conference that adopts SI’s specifications, BIPM as the technical body that maintains and documents them — analogous to how the World Customs Organization custodies the Harmonized System that SIEC cross-references (see SIEC Classification System).

Role in IRES

SI is not itself an energy-statistics standard, but IRES leans on it in two ways: its seven base units and prefix system are the reference point IRES uses to define “original” measurement units, and the joule — SI’s own coherent derived unit of energy — is the unit IRES recommends as the common unit for cross-product energy comparison [IRES, Ch. IV, para. 4.27, PDF p. 58, 2018]. See Measurement Units for the full base-unit and prefix tables, and Calorific Values for how calorific values convert original units into that common, joule-denominated basis.

Related

• Measurement Units — SI base units, derived units, prefixes, and their application to original and common units in energy statistics
• IRES Chapter IV — Measurement Units and Conversion Factors — the chapter digest this page supports
• International Recommendations for Energy Statistics — IRES, which defines measurement units and conversion factors in its Chapter IV