New prefixes added to the SI Units of Measurements

New prefixes to add to the world’s largest and smallest numbers have been confirmed by a vote at the 27th General Conference on Weights and Measures (CGPM) in Versailles, France, on Friday 18 November 2022.

The International Committee for Weight and Measures (CIPM) is responsible for the International System of Units (the SI), and propose changes or additions to the States party to the Metre Convention for consideration at the CGPM, that takes place at least every four years. This year, the CIPM presented a draft resolution to the Conference “On the extension of the range of SI prefixes”. The meeting unanimously adopted the resolution and decided “to add to the list of SI prefixes to be used for multiples and submultiples of units the following prefixes:

Multiplying factor Name Symbol

1027 ronna R

10−27 ronto r

1030 quetta Q

10−30 quecto q

This change was necessitated by the increasing amount of data that requires measurement

Dr Wynand Louw from the NMISA, who serves as the current President of the CIPM, commented that the continual update of the International System of Units is of the utmost importance for the scientific world. “The 27th CGPM considered:

• the essential role of the International System of Units (SI) in providing confidence in the accuracy and global comparability of measurements needed for international trade, manufacturing, human health and safety, protection of the environment, global climate studies and scientific research,
• the benefits of encouraging the use of SI units by providing new SI prefixes for scientific

communities that depend on measurements that are not covered by the current range,

• the needs of data science in the near future to express quantities of digital information

expressed using orders of magnitude in excess of 1024,

• the importance of timely action to prevent unofficial prefix names being de facto adopted

in other communities,

and adopted the resolution unanimously.

The new prefixes have been incorporated into the SI with immediate effect, and the Si brochure (the 9th edition is currently in use) will be updated by the CIPM to reflect the new prefixes.

According to Dr Richard Brown, the Head of Metrology at the UK’s National Physical Laboratory, who led the proposal for the change in the Consultative Committee for Units, the CCU, these new prefixes simplify how we measure and report on objects, for instance, the weight of the earth. “If we think about mass, the Earth weighs approximately six ronnagrams,” which is a six followed by 27 zeroes”.

More about this addition and other Resolutions adopted by the Conference can be read on the International Bureau of Weights and Measures (BIPM) website page on the CGPM/2022-Resolutions, located at https://www.bipm.org/en/home

About NMISA (The National Metrology Institute of South Africa)

NMISA is a member of the Department of Trade, Industry, and Competition’s (the dtic) family and part of the technical infrastructure entities. The entity is tasked with the development, maintenance, and dissemination of measurement standards that assist South Africa in global trade and ensure that the country can react to food safety crises as they arise.

NMISA’s mission is to be the leading Metrology Centre of excellence on the African continent connecting Africa to the world. It aims to consistently deliver outstanding innovative and internationally comparable measurement solutions that support regional and international trade, people’s quality of life, and enable the protection of the environment. NMISA provides services accredited to ISO/IEC 17025, is the producer of Reference Materials accredited to ISO 17034, and is a provider of ISO/IEC 17043 accredited Proficiency Testing schemes.