The BIPM has published a new version of the SI Brochure
The BIPM published version 3.01 of the 9th edition of the SI Brochure on 28 August 2024. The International System of Units (SI) is the only globally agreed system of units and the SI Brochure is the authoritative document describing the system, its operation and application.
The 9th edition, published in 2019, reflects the major revision of the SI agreed at the 26th General Conference on Weights and Measures (CGPM) in 2018, and which was implemented on 20 May 2019.
Significant improvements or technical changes result in the publication of a new version of the Brochure and version 3.01, published in August 2024, incorporates several improvements to the description of units for angles and of quantities with the unit one, which were prepared by a task group of the Consultative Committee for Units (CCU). This update has not resulted in any changes to the status of these quantities or their units within the SI but has provided clarification, harmonized language, improved understanding, acknowledged nuance and reflects new consensus in understanding and terminology. An important improvement has been the strengthening of the guidance that explicit units should be employed wherever possible for quantities with the unit one.
Version 3.01 of the 9th edition of the SI Brochure is available from the BIPM web site in English and French.