General Conference on Weights and Measures facts for kids

The General Conference on Weights and Measures (or CGPM) is like the main boss of the International Bureau of Weights and Measures (BIPM). This group was started in 1875 by a special agreement called the Metre Convention. Its job is to help countries work together on how we measure things, like length and weight.

The CGPM is made up of people sent by the governments of member countries. It also has observers from other countries that are "Associates." The CGPM chooses another group called the International Committee for Weights and Measures (CIPM). This committee helps guide and manage the BIPM.

At first, the BIPM mainly focused on the kilogram (for weight) and the metre (for length). But in 1921, they decided to include all kinds of measurements and everything about the metric system. In 1960, the 11th CGPM meeting officially named the system we use today: the International System of Units, or "SI" for short.

The General Conference looks at reports from the CIPM about their work. They talk about how to make the International System of Units (SI) better and more widely used. They also approve new scientific discoveries about measurements and make big decisions about how the BIPM is run, including its money.

The CGPM usually meets in Paris every four years. The 25th meeting was in November 2014. The 26th meeting was in Versailles in November 2018. The 27th meeting happened in November 2022.

How the CGPM Was Started

On May 20, 1875, 17 countries signed an international agreement called the Metre Convention. This agreement created the International Bureau of Weights and Measures (BIPM). The BIPM has two main parts that run it:

• The General Conference on Weights and Measures (CGPM): This is the big meeting where official people from member countries gather. It's the highest authority for all decisions.
• The International Committee for Weights and Measures (CIPM): This group has scientists and experts in measurement. They prepare and carry out the decisions made by the CGPM. They also supervise the BIPM.

The BIPM has its own lab and offices. Their work includes setting up the main standards for important measurements and keeping the international models of these standards safe.

The CGPM works for the governments of its member countries. It chooses the members of the CIPM. It also gets reports from the CIPM and shares them with governments and national labs. The CGPM looks at and approves changes to the International System of Units (SI). It also approves the budget for the BIPM and makes all the big decisions about how the BIPM works and grows.

You can think of the BIPM like a company. The CGPM is like the meeting of all the shareholders (the owners). The CIPM is like the board of directors chosen by the shareholders. And the staff at the BIPM's location in Saint-Cloud, France, do the daily work.

Who Can Join the CGPM?

The CGPM has two types of members:

• Full members: These are countries that want to be fully involved in the BIPM's activities.
• Associate members: These are countries or economies that only want to join a specific program for recognizing measurement standards. Associate members can attend CGPM meetings as observers.

To be a full member, a country usually needs to have diplomatic relations with France. This is because all official communication between the organization and national governments goes through the country's ambassador to France. Even during world wars, countries fighting France kept their membership. The meetings are led by the President of the French Academy of Sciences.

In 1875, 17 out of 20 countries at the first meeting signed the convention. The United Kingdom joined in 1884. By 2001, there were 49 members. As of November 18, 2022, there are 64 Member States and 37 Associate States and Economies.

Member Countries

Past Member Countries

Associate Countries

In 1999, the CGPM created the "associate" category. This was for countries not yet full BIPM members and for groups of countries working together economically.

Past Associate Countries

Important CGPM Meetings

The CGPM meetings have made many important decisions about how we measure things. Here are some key ones:

International Committee for Weights and Measures (CIPM)

The International Committee for Weights and Measures (CIPM) has eighteen members, each from a different country. They are chosen by the CGPM. Their main job is to make sure that measurement units are the same all over the world. They do this by taking action themselves or by suggesting ideas to the CGPM.

The CIPM meets every year at the Pavillon de Breteuil in France. They discuss reports from their special "Consultative Committees." The reports from the CGPM, CIPM, and all the Consultative Committees are published by the BIPM.

CIPM's Purpose

The CIPM's main office is in Saint-Cloud, Hauts-de-Seine, France.

In 1999, the CIPM created the CIPM Mutual Recognition Arrangement (MRA). This agreement helps countries accept each other's measurement standards. It also recognizes that calibration and measurement certificates from national measurement labs are valid.

Recently, the CIPM has focused on updating the SI.

Consultative Committees

The CIPM has set up several Consultative Committees (CCs) to help with its work. These committees are guided by the CIPM. The head of each committee is usually a member of the CIPM. Most committees are open to national measurement labs from member countries that are experts in that field. Labs from member countries that are active but not experts can attend as observers.

These committees include:

• CCAUV: For Acoustics, Ultrasound, and Vibration
• CCEM: For Electricity and Magnetism
• CCL: For Length
• CCM: For Mass and related measurements
• CCPR: For Photometry (light measurement) and Radiometry (radiation measurement)
• CCQM: For Amount of Substance – measurements in Chemistry and Biology
• CCRI: For Ionizing Radiation
• CCT: For Thermometry (temperature measurement)
• CCTF: For Time and Frequency
• CCU: For Units

The CCU's job is to give advice on how the SI system should grow and to help create the SI brochure. It also works with other international groups like the ISO and the IAU.

Important Reports

The CIPM publishes official reports, including:

• Reports of CIPM meetings
• An annual report to governments about the BIPM's money and management
• Information about how much each member country needs to contribute
• Invitations to CGPM meetings
• A report from the CIPM President to the CGPM

Sometimes, the CGPM asks the CIPM to do big studies about things that affect the CGPM or BIPM. Here are some of those reports:

The Blevin Report

The Blevin Report came out in 1998. It looked at the state of measurement science around the world. The report suggested that the BIPM should work more closely with other groups. It also said that developing countries should be more involved in the world of measurement.

The Kaarls Report

The Kaarls Report, published in 2003, looked at how the BIPM's role was changing. It focused on the growing need for accurate measurements in trade, industry, and society.

The SI Brochure

The CIPM is in charge of the SI brochure. This brochure officially defines the International system of units. The CCU creates the brochure with other international organizations. At first, it was only in French. Now, newer versions are published in both English and French at the same time. The French text is the official one. The 9th edition came out in 2019 and was updated in December 2022 to include the newest SI prefixes.

See also

In Spanish: Conferencia General de Pesas y Medidas para niños

• History of the metre
• Outline of the metric system