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The metric system is a system of measurement that is used around the world. It developed from a system introduced by France in 1795. Before 1795 many towns in France had their own system of measurement. The metric system is based on decimals (units of ten). It was designed to have a logical structure.

By 1875 many countries in Europe and in Latin America had changed to using the metric system. In 1875 seventeen countries Metre Convention agreed to use the same standard as each other for their measurement systems. A new organization called the International Bureau of Weights and Measures (BIPM) was set up. The reference standard that everybody used is kept at the BIPM headquarters.

In 1960 the metric system was given a new name - the International System of Units (which is often written "SI" for short).

In the 1970s many people in the United Kingdom and the rest of the Commonwealth started using the metric system at their places of work. The United States is the only major country where the metric system is not in widespread use.

Administering the metric system[change | change source]

Seal of the BIPM

In 1875 members of governments from twenty different countries met in Paris to discuss weights and measures. Seventeen of the countries signed an treaty about weights and measures. The treaty was called "The Convention of the Metre". They agreed:[1][2][3]

  • To set up an inter-governmental organisation to administer the treaty. This organization was called the International Bureau of Weights and Measures (BIPM).
  • France was to have responsibility for acquiring suitable premises for the BIPM. These premises would become neutral territory. The BIPM offices and laboratories would be located on the site.
  • To make 40 identical copies of the kilogram. One was chosen as the prototype (or primary) copy. This copy was known as the "International Prototype Kilogram". It replaced the Kilogramme des archives as the world's primary copy of the kilogram. The Kilogramme des archives would be kept at the BIPM premises.
  • To make 30 identical copies of the metre. One was chosen as the prototype (or primary) copy. This copy was known as the "International Prototype Metre". It replaced the Metre des archives as the world's primary copy of the metre. The Metre des archives would be kept at the BIPM premises.
  • To give one copy of the metre and one copy of the kilogram to each country. These would be called "national prototype metres" and "national prototype kilograms".
  • To compare the national prototype metres and kilograms against the international prototypes at regular intervals.
  • To promote the use of the metric system.

In 1889 the copies of the kilogram and the metre were ready to be given to the different countries that signed the treaty.[3]

The United States signed the treaty in 1878.[4] The United Kingdom signed the treaty 1884.[5] Neither country passed laws making it compulsory to use the metric system.

Litre[change | change source]

The outline of the metric system was first defined in 1791. Two units of measure were proposed. They were the metre and the kilogram. Other units of measure were to be proposed later. A preliminary definition of the metric system was published in 1793. In it, the pinte was defined as being equivalent to a cube with sides 10 cm. Previously, the pinte was a old French unit of measure of capacity. In 1795 the definition was revised. The pinte was given the name litre.[6]

In 1795 the kilogram was defined to be exactly one litre of water a 4 °C. In 1799 the kilogram was redefined. The new definition said that the kilogram was the mass of the kilogram des archives. In 1901 scientists measured the volume of one litre of water at 4 °C very carefully.[Note 1] They found that it was about 0.9999097 dm3. The BIPM redefined the litre as being exactly the volume of one kilogram of water at 4 °C.[7]

In 1960 the SI was introduced. The BIPM changed the definition of the litre back to "one dm3". They defined the litre[Note 2] This was because they were used in a lot of countries. The BIPM said that the litre should not be used very very accuate work.[8]

According to SI rules, the symbol for the litre should be "l". This is because the litre was not named after somebody whose name was "Litre".[Note 3] However the symbol "l" and the number "1" are easily confused. In 1979 the BIPM made an exception for the symbol for the litre. They said that people could use either "L" or "l" as its symbol.[9]

  1. Water has its maximum density at 4 °C.
  2. The are and the tonne) were also defined as "Non-SI units accepted for use with the SI".
  3. For example, the symbol for watts is "W" because watts were named after James Watt.

Towards SI[change | change source]

During the late nineteenth and early twentieth century many new units of measure were defined using the metric system. Units of measure used in electrostatic applications, electromagnetic applications and electrical distribution systems were incompatible with each other.[10] The use of standard gravity in force and pressure definitions resulted in more units of measure being defined than were necessary.

After the Second World War the International Union of Pure and Applied Physics (IUPAP) and the French Government asked the BIPM to look into the matter. In 1948, the 9th CGPM asked the CIPM to conduct a study into units of measurement used by member states.[11] The CIPM reported back and in 1954 the 10th CGPM decided to set up a new system of units. There would be six base units. These were the metre, kilogram, second, ampere, degree Kelvin (later renamed kelvin), and candela. The new system was published in 1960. The 11th CGPM named it the International System of Units. The short name was "SI". This came from the French name, [Le Système international d'unités] error: {{lang}}: text has italic markup (help).[12]:110[13] The BIPM described SI as "the modern metric system".[12]:95

Since 1960 the BIPM has made several refinements to SI. Some of the refinements include developing new ways of making high precision measurement. Other refinements include small changes to details of definitions.

Creating an IBAN[change | change source]

  1. Create the BBAN using national rules.
  2. Add the country code to the end of the string.
  3. Add "00" to the end of the string.
  4. Replace the letter "A" with "10", the letter "B" with "11" and so on.
  5. Divide the number by 97 and save the remainder.
  6. Subtract the remainder from 98. This give the checksum chararacters.
  7. If the checksum is less than "10", place a "0" infron of the checksum.
  8. The IBAN is made by joining the country code, the checksum and the BBAN.

GB29 NWBK 6016 1331 9268 19


  • A British bank account at the National Westminster Bank has sort code code "60-16-13".
  • The account number is "31926819".
  • The BIC for the National Westminster Bank is "NWBK".
  • Calculate the checksum
*The BBAN is WEST12345698765432
*Convert to all numbers 3114282912345698765432
*Remainder when dividing by 97 16
*Checksum is 98 - 16 = 82
  • The IBAN is xxxx

References[change | change source]

  1. "The Treaty of the Meter". National Institute of Standards and Technology. 3 September 2009. Retrieved 6 February 2014.
  2. "Photo of the International Bureau of Weights and Measures in Sevres". National Institute of Standards and Technology. Retrieved 6 February 2014.
  3. 3.0 3.1 Judson, Lewis V (October 1963). Weights and measures standards of the United States: a brief history. NBS Special publication 447. Washington DC: National Bureau of Standards. pp. 14–16. Retrieved 6 February 2014. Unknown parameter |loc= ignored (help)
  4. "The United States of America". International Bureau of Weights and Measures. Retrieved 26 February 2014.
  5. "The United Kingdom of Great Britain and Northern Ireland". International Bureau of Weights and Measures. Retrieved 26 February 2014.
  6. Hellman, C. Doris (Jan 1936). "Legendre and the French Reform of Weights and Measures". Orsis (University of Chicago): 314-340. 
  7. "Resolution of the 3rd meeting of the CGPM (1901)". BIPM. Retrieved 5 March 2014.
  8. "Resolution 6 of the 12th meeting of the CGPM (1964)". BIPM. Retrieved 5 March 2014.
  9. "Resolution 6 of the 16th meeting of the CGPM (1979)". BIPM. Retrieved 5 March 2014.
  10. Fenna, Donald (2002). Weights, Measures and Units. Oxford University Press. International unit. ISBN 0-19-860522-6.
  11. 9th CGPM (1948): Resolution 6
  12. 12.0 12.1 Cite error: The named reference SIBrochure was used but no text was provided for refs named (see the help page).
  13. 11th CGPM (1960): Resolution 12

Metrication by year map

References[change | change source]