General Conference on Weights and Measures


The General Conference on Weights and Measures is the supreme authority of the International Bureau of Weights and Measures, the inter-governmental organization established in 1875 under the terms of the Metre Convention through which Member States act together on matters related to measurement science and measurement standards. The CGPM is made up of delegates of the governments of the Member States and observers from the Associates of the CGPM. Under its authority, the International Committee for Weights and Measures executes an exclusive direction and supervision of the BIPM.
The General Conference receives the report of the CIPM on work accomplished; it discusses and examines the arrangements required to ensure the propagation and improvement of the International System of Units ; it endorses the results of new fundamental metrological determinations and various scientific resolutions of international scope; and it decides all major issues concerning the organization and development of the BIPM, including the dotation of the BIPM.
The CGPM meets in Paris, usually once every four years. The 25th meeting of the CGPM took place from 18 to 20 November 2014, and the 26th meeting of the CGPM took place in Versailles from 13 to 16 November 2018.
Initially the Metre Convention was only concerned with the kilogram and the metre, but in 1921 the scope of the treaty was extended to accommodate all physical measurements and hence all aspects of the metric system. In 1960 the 11th CGPM approved the International System of Units, usually known as "SI".

Establishment

On 20 May 1875 an international treaty known as the Convention du Mètre was signed by 17 states. This treaty established an international organisation, the Bureau international des poids et mesures, consisting of:
The CGPM acts on behalf of the governments of its members. In so doing, it appoints members to the CIPM, receives reports from the CIPM which it passes on to the governments and national laboratories on member states, examines and where appropriate approves proposals from the CIPM in respect of changes to the International System of Units, approves the budget for the BIPM and it decides all major issues concerning the organization and development of the BIPM.
The structure is analogous to that of a stock corporation. The BIPM is the organisation, the CGPM is the general meeting of the shareholders, the CIPM is the board of directors appointed by the CGPM, and the staff at the site in Saint-Cloud perform the day-to-day work.

Membership criteria

The CGPM recognises two classes of membership – full membership for those states that wish to participate in the activities of the BIPM and associate membership for those countries or economies that only wish to participate in the CIPM MRA program. Associate members have observer status at the CGPM. Since all formal liaison between the convention organisations and national governments is handled by the member state's ambassador to France, it is implicit that member states must have diplomatic relations with France, though during both world wars, nations that were at war with France retained their membership of the CGPM. CGPM meetings are chaired by the Président de l'Académie des Sciences de Paris.
Of the twenty countries that attended the Conference of the Metre in 1875, representatives of seventeen signed the convention on 20 May 1875. In April 1884 HJ Chaney, Warden of Standards in London unofficially contacted the BIPM inquiring whether the BIPM would calibrate some metre standards that had been manufactured in the United Kingdom. Broch, director of the BIPM replied that he was not authorised to perform any such calibrations for non-member states. On 17 September 1884, the British Government signed the convention on behalf of the United Kingdom. This number grew to 21 in 1900, 32 in 1950, and 49 in 2001., there are 59 Member States and 42 Associate States and Economies of the General Conference :

Member States

Argentina
Australia
Austria
Belgium
Brazil
Bulgaria
Canada
Chile
China
Colombia

Croatia
Czech Republic
Denmark
Egypt
Finland
France
Germany
Greece
Hungary
India
Indonesia
Iran
Iraq
Ireland
Israel
Italy
Japan
Kazakhstan
Kenya
Lithuania
Malaysia
Mexico
Montenegro
Netherlands
New Zealand
Norway
Pakistan
Poland
Portugal
Romania
Russian Federation
Saudi Arabia
Serbia
Singapore
Slovakia
Slovenia
South Africa
South Korea
Spain
Sweden
Switzerland
Thailand
Tunisia
Turkey
Ukraine
United Arab Emirates
United Kingdom
United States
Uruguay

Associates

At the 21st meeting of the CGPM in October 1999, the category of "associate" was created for states not yet BIPM members and for economic unions.
Albania
Azerbaijan
Bangladesh
Belarus
Bolivia
Bosnia and Herzegovina
Botswana
Caribbean Community
Chinese Taipei
Costa Rica
Cuba
Ecuador
Estonia
Ethiopia
Georgia
Ghana
Hong Kong
Jamaica
Kuwait
Latvia
Luxembourg
Malta
Mauritius
Moldova
Mongolia
Namibia
North Macedonia
Oman
Panama
Paraguay
Peru
Philippines
Qatar
Seychelles
Sri Lanka
Sudan
Syria
Tanzania
Uzbekistan
Vietnam
Zambia
Zimbabwe

CGPM meetings

International Committee for Weights and Measures

The International Committee for Weights and Measures consists of eighteen persons, each of a different nationality elected by the General Conference on Weights and Measures whose principal task is to promote worldwide uniformity in units of measurement by taking direct action or by submitting proposals to the CGPM.
The CIPM meets every year at the Pavillon de Breteuil where, among other matters, it discusses reports presented to it by its Consultative Committees. Reports of the meetings of the CGPM, the CIPM, and all the Consultative Committees, are published by the BIPM.

Mission

The is based in Saint-Cloud, Hauts-de-Seine, France.
In 1999 the CIPM has established the CIPM Arrangement de reconnaissance mutuelle which serves as the framework for the mutual acceptance of national measurement standards and for recognition of the validity of calibration and measurement certificates issued by national metrology institutes.
A recent focus area of the CIPM has been the revision of the SI.

Consultative committees

The CIPM has set up a number of consultative committees to assist it in its work. These committees are under the authority of the CIPM. The president of each committee, who is expected to take the chair at CC meetings, is usually a member of the CIPM. Apart from the CCU, membership of a CC is open to National Metrology Institutes of Member States that are recognized internationally as most expert in the field. NMIs from Member States that are active in the field, but lack the expertise to become Members, are able to attend CC meetings as observers.
These committees are:
The CCU's role is to advise on matters related to the development of the SI and the preparation of the SI brochure. It has liaison with other international bodies such as International Organization for Standardization, International Astronomical Union, International Union of Pure and Applied Chemistry and International Union of Pure and Applied Physics.

Major reports

Official reports of the CIPM include:
From time to time the CIPM has been charged by the CGPM to undertake major investigations related to activities affecting the CGPM or the BIPM. Reports produced include:

The Blevin Report

The Blevin Report, published in 1998, examined the state of worldwide metrology. The report originated from a resolution passed at the 20th CGPM which committed the CIPM to
The report identified, amongst other things, a need for closer cooperation between the BIPM and other organisations such as International Organization of Legal Metrology and International Laboratory Accreditation Cooperation with clearly defined boundaries and interfaces between the organisations. Another major finding was the need for cooperation between accreditation laboratories and the need to involve developing countries in the world of metrology.

The Kaarls Report

The Kaarls Report published in 2003 examined the role of the BIPM in the evolving needs for metrology in trade, industry and society.

SI Brochure

The CIPM has responsibility for commissioning the SI brochure, which is the formal definition of the International system of units. The brochure is produced by the CCU in conjunction with a number of other international organisations. Initially the brochure was only in French – the official language of the metre convention, but recent versions have been published simultaneously in both English and French, with the French text being the official text. The 6th edition was published in 1991, the 7th edition was published in 1998, and the 8th in 2006.
The most recent edition is the 9th edition, published in 2019.