France has a unique history of units of measurement due to the radical decision to invent and adopt the metric system after the French Revolution.

- Ancien régime (to 1795)
- Revolutionary France (1795–1812)
- Mesures usuelles (1812–1839)
- The metric system restored (1840–1875)
- International era (1875 onwards)
- See also
- References

In the Ancien régime, before 1795, France used a system of measures that had many of the characteristics of the modern Imperial System of units. There was widespread abuse of the king's standards to the extent that the *lieue* could vary from 3.268 km in Beauce to 5.849 km in Provence. In the revolutionary era, France used the first version of the metric system. This system was not well received by the public. Between 1812 and 1837, the * mesures usuelles * was used – traditional names were restored, but were based on metric units: for example, the livre became 500 g. After 1837, the metric system was reintroduced and has remained the principal system of use to this day.

In the pre-revolutionary era (before 1795), France used a system of measures that had many of the characteristics of the modern Imperial System of units, but there was no unified system of measurement. Charlemagne and successive kings had tried but failed to impose a unified system of measurement in France.^{ [1] } (In England, by contrast, the Magna Carta decreed that "there shall be one unit of measure throughout the realm.")

The names and relationships of many units of measure were adopted from Roman units of measure and many more were added – it has been estimated that there were seven or eight hundred different names for the various units of measure. In addition, the quantity associated with each unit of measure differed from town to town and even from trade to trade to such an extent that the *lieue* (league) could vary from 3.268 km in Beauce to 5.849 km in Provence. It has been estimated that, on the eve of the Revolution, a quarter of a million different units of measure were in use in France.^{ [2] } Although certain standards, such as the *pied du roi* (the king's foot) had a degree of pre-eminence and were used by savants across Europe, many traders chose to use their own measuring devices, giving scope for fraud and hindering commerce and industry.^{ [1] }

As an example, the weights and measures used at Pernes-les-Fontaines in southeastern France differ from those catalogued later in this article as having been used in Paris. In many cases, the names are different, while the *livre* is shown as being 403 g, as opposed to 489 g – the value of the *livre du roi*. (The Imperial pound is about 453.6 g.)

The French Revolution and subsequent Napoleonic Wars marked the end of the Age of Enlightenment. The forces of change that had been brewing manifest themselves across all of France, including the way in which units of measure should be defined. The savants of the day favoured the use of a system of units that were inter-related and which used a decimal basis.

There was also a wish that the units of measure should be for all people and for all time and therefore not dependent on an artefact owned by any one particular nation. Talleyrand, at the prompting of the savant Condorcet, approached the British and the Americans in the early 1790s with proposals of a joint effort to define the metre. In the end, these approaches came to nothing and France decided to "go it alone".^{ [3] }

Decimal time was introduced in the decree of 5 October 1793 under which the day was divided into 10 "decimal hours", the "hour" into 100 " decimal minutes" and the "decimal minute" into 100 "decimal seconds". The "decimal hour" corresponded to 2 hr 24 min, the "decimal minute" to 1.44 min and the "decimal second" to 0.864 s.

The implementation of decimal time proved an immense task and under the article 22 of the law of 18 Germinal, Year III (7 April 1795), the use of decimal time was no longer mandatory.^{ [4] } On 1 January 1806, France reverted to the traditional timekeeping.^{ [5] }

The metric system of measure was first given a legal basis in 1795 by the French Revolutionary government. Article 5 of the law of 18 Germinal, Year III (7 April 1795) defined five units of measure. The units and their preliminary values were:^{ [6] }

- The metre, for length – defined as being one ten millionth of the distance between the North Pole and the Equator through Paris
- The are (100 m
^{2}) for area [of land] - The stère (1 m
^{3}) for volume of firewood - The litre (1 dm
^{3}) for volumes of liquid - The gram, for mass – defined as being the mass of one cubic centimetre of water

Decimal multiples and submultiples of these units would be defined by Greek prefixes - "myria", "kilo", "hecta" (100), "deka" - and Latin prefixes - "deci", "centi" and "milli". Using Cassini's survey of 1744, a provisional value of 443.44 *lignes* was assigned to the metre which, in turn, defined the other units of measure.^{ [7] }

The final value of the metre had to wait until 1799, when Delambre and Mechain presented the results of their survey between Dunkirk and Barcelona that fixed the length of the metre at 443.296 *lignes*. The law 19 Frimaire An VIII (10 December 1799) defined the metre in terms of this value and the kilogram as being 18,827.15 *grains*. These definitions enabled the construction of reference copies of the kilogram and metre, which were to be used as standards for the next 90 years.

At the same time, a new decimal-based system for angular measurement was implemented. The right angle was divided into 100 *grads*, which in turn was divided in 100 *centigrads*. An arc on the earth’s surface formed by an angle of one *centigrad* was one kilometre.

The metric system was introduced into France in 1795 on a district by district basis, starting with Paris. However, by modern standards, the introduction was poorly managed. Although thousands of pamphlets were distributed, the Agency of Weights and Measures, which oversaw the introduction, underestimated the work involved. Paris alone needed 500,000 metre sticks, yet one month after the metre became the sole legal unit of measure, there were only 25,000 in store.^{ [8] } This, combined with other excesses of the Revolution made the metric system unpopular.

Napoleon ridiculed the metric system, but as an able administrator, he recognised the value of a sound basis for a system of measurement. Under the *décret impérial du 12 février 1812* (imperial decree of 12 February 1812), he introduced a revised system of measure – the *mesures uselles* or "customary measures" for use in small retail businesses. However, all government, legal and similar works still had to use the metric system and the metric system continued to be taught at all levels of education.^{ [9] } The names of many pre-metric units were reintroduced, but were redefined in terms of metric units. Thus the *toise* (fathom) was defined as being two metres with six *pied* (feet) making up one *toise*, twelve *pouce* (inches) making up one *pied* and twelve *lignes* making up one *pouce*. Likewise, the *livre* (pound) was defined as being 500 g, each *livre* comprising sixteen *once* and each *once* eight *gros* and the *aune* as 120 centimetres.^{ [10] }

*La loi du 4 juillet 1837* (the law of 4 July 1837) effectively revoked the use of *mesures usuelles* by reaffirming the laws of measurement of 1795 and 1799 to be used from 1 May 1840.^{ [1] } However, many units of measure, such as the *livre*, remained in colloquial use for many years and the *livre* still does to some extent.

When this legislation was introduced, the metric system was beginning to take hold across Europe. Switzerland and the German state of Baden had both defined their *Fuß* (foot) as being 300 mm and the German state of Hessen-Darmstadt has defined its *Fuß* as being 250 mm. Moreover, the Netherlands, Belgium, Greece, Lombardy and Venice had all adopted the metric system, albeit with local names for the "metre", "kilogram" and so on.^{ [11] } The metric system was given a boost when the German * Zollverein * (Customs Union) introduced the *Zollpfund* of 500 g in 1850.

The Great Exhibition of 1851 in London was followed by international exhibitions in Paris in 1855 and 1867. The 1867 exhibition had a stand showing how the diverse units of measure were converging onto the metric system – a system that had been developed in France and whose standards were in the custody of the French government, but available for world use.^{ [12] }

In 1870, while France was preparing to host an international conference to discuss international cooperation in the sphere of units of measurement, the war broke out. France was humiliated by Prussia's military action, but in 1872 France seized the diplomatic initiative and re-issued the invitations for the 1870 conference. The conference met in 1875 and concluded with the signing of the Treaty of the Metre. The principal agreements under the treaty were:^{ [13] }

- A three-tier organisation would be put into place to provide political (CGPM), scientific (CIPM) and secretarial (BIPM) support for coordinating calibrations of national standards against an international standard.
- One of the eighteen seats on the CIPM would always be filled by a Frenchman.
- France would provide premises for the secretariat. These premises, at the Pavillon de Breteuil, near Paris would have a diplomatic status.
- New prototypes of the kilogram and metre would be manufactured. These were ultimately made in England and delivered in 1889.
^{ [14] }

Thus the French metre and kilogram passed into international control.

During the early part of the twentieth century, the French introduced their own units of power - the * poncelet *, which was defined as being the power required to raise a mass of 100 kg against standard gravity with a velocity of 1 m/s giving a value of 980.665 W.^{ [15] }^{ [16] } However, many other European countries defined their units of power (the *Pferdestärke* in Germany, the *paardekracht* in the Netherlands and the *cavallo vapore* in Italy) using 75 kg rather than 100 kg, which gave a value of 735.49875 W (about 0.985 HP). Eventually, the *poncelet* was replaced with the *cheval vapeur*, which was identical to equivalent units of measure in neighbouring countries. In 1977, these units, along with the *stere* and the *livre* (and amongst others, the German *pfund*) were proscribed by EEC Directive 71/354/EEC ^{ [17] } which required EU member states to standardise on the International System of Units (SI) and therefore to use the watt and its multiples.

The **kilogram** is the base unit of mass in the metric system, formally the International System of Units (SI), having the unit symbol **kg**. It is a widely used measure in science, engineering, and commerce worldwide, and is often simply called a **kilo** in everyday speech.

The **litre** or **liter** is a non-SI unit of volume. It is equal to 1 cubic decimetre (dm^{3}), 1,000 cubic centimetres (cm^{3}) or 0.001 cubic metre. A cubic decimetre occupies a volume of 10 cm × 10 cm × 10 cm and is thus equal to one-thousandth of a cubic metre.

**Metrication** or **metrification** is the act or process of converting the system of measurement traditionally used in a country to the metric system. Worldwide, there has been a process of nations transitioning from their various local and traditional units of measurement, to the metric system. This process first began in France during the 1790s and has continued extensively world-wide over the following two centuries, but the metric system has not been fully adopted in all countries and sectors.

A **nautical mile** is a unit of measurement used in both air and marine navigation, and for the definition of territorial waters. Historically, it was defined as one minute of latitude along any line of longitude. Today the international nautical mile is defined as exactly 1852 metres. The derived unit of speed is the knot, one nautical mile per hour.

The **International System of Units** is the modern form of the metric system and is the most widely used system of measurement, based on the International System of Quantities. It comprises a coherent system of units of measurement built on seven base units, which are the second, metre, kilogram, ampere, kelvin, mole, candela, and a set of twenty prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units. The system also specifies names for 22 derived units, such as lumen and watt, for other common physical quantities.

**Metric system** refers to the internationally recognised decimalised system of measurement known as the International System of Units (SI), or to one of its predecessors. It is in widespread use, and where it is adopted, it is the only or most common system of weights and measures. It is used to measure everyday things such as the mass of a sack of flour, the height of a person, the speed of a car, and the volume of fuel in its tank. It is also used in science, industry and trade.

**Metrology** is the science of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in France, when a length standard taken from a natural source was proposed. This led to the creation of the decimal-based metric system in 1795, establishing a set of standards for other types of measurements. Several other countries adopted the metric system between 1795 and 1875; to ensure conformity between the countries, the Bureau International des Poids et Mesures (BIPM) was established by the Metre Convention. This has evolved into the International System of Units (SI) as a result of a resolution at the 11th Conference Generale des Poids et Mesures (CGPM) in 1960.

The **gram** is a metric system unit of mass.

The **quintal** or **centner** is a historical unit of mass in many countries which is usually defined as 100 base units of either pounds or kilograms. It is commonly used for grain prices in wholesale markets in India, where 1 quintal = 100 kg.

**Mesures usuelles** were a French system of measurement introduced by Napoleon I in 1812 to act as compromise between the metric system and traditional measurements. The system was restricted to use in the retail industry and continued in use until 1840, when the laws of measurement from the 1795 and 1799 were reinstituted.

The **"Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States"** was a report submitted to the U.S. House of Representatives on July 13, 1790, by Secretary of State Thomas Jefferson.

A **system of measurement** is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of science and commerce. Systems of measurement in use include the International System of Units (SI), the modern form of the metric system, the imperial system, and United States customary units.

The spread of metrication around the world in the last two centuries has been met with both support and opposition. All countries except Liberia have adopted the Metric System as their primary system of measurement, although Liberia has seen some introduction of metric units. The United States of America officially accepted the Metric System in 1878 but United States customary units, albeit defined by reference to the SI system of units, remain ubiquitous outside the science and technology sector. The metric system has been largely adopted in the United Kingdom, Canada and Ireland, without having fully displaced imperial units from all areas of life. In other Anglophone countries such as Australia, Singapore and New Zealand, imperial units have been formally deprecated and are no longer officially sanctioned for use.

The **grave** was the original name of the kilogram, in the preliminary version of the metric system between 1793 and 1795.

The **hectare** is a non-SI metric unit of area equal to a square with 100-metre sides, or 10,000 m^{2}, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is about 0.405 hectare and one hectare contains about 2.47 acres.

**French units** could refer to any of:

Before the French Revolution, which started in 1789, French units of measurement were based on the Carolingian system, introduced by the first Holy Roman Emperor Charlemagne (800–814 AD) which in turn were based on ancient Roman measures. Charlemagne brought a consistent system of measures across the entire empire. However, after his death, the empire fragmented and many rulers introduced their own variants of the units of measure.

The **history of the metric system** began in the Age of Enlightenment with notions of length and weight taken from natural ones, and decimal multiples and fractions of them. The system became the standard of France and Europe in half a century. Other dimensions with unity ratios were added, and it went on to be adopted by the world.

The metric system was developed during the French Revolution to replace the various measures previously used in France. The metre is the unit of length in the metric system and was originally based on the dimensions of the earth, as far as it could be measured at the time. The litre, is the unit of volume and was defined as one thousandth of a cubic metre. The metric unit of mass is the kilogram and it was defined as the mass of one litre of water. The metric system was, in the words of French philosopher Marquis de Condorcet, "for all people for all time".

The following outline is provided as an overview of and topical guide to the **metric system** – various loosely related systems of measurement that trace their origin to the decimal system of measurement introduced in France during the French Revolution.

- 1 2 3 "History of measurement". Métrologie française. Retrieved 2011-02-06.
- ↑ Adler, Ken (2002).
*The Measure of All Things: The Seven-Year Odyssey That Transformed the World*. Nepal: Jay Prajapatri. pp. 2–3. ISBN 0349115079. - ↑ Adler. pp. 88–96.Missing or empty
`|title=`

(help) - ↑ "Décret relatif aux poids et aux mesures. 18 germinal an 3 (7 avril 1795)".
*Le systeme metrique decimal*(in French). Retrieved 2011-02-07. - ↑ "Dials & Symbols of the French revolution. The Republican Calendar and Decimal time". The Horological Foundation. Retrieved 2011-02-07.
- ↑ "La loi du 18 Germinal an 3 (The law of 18 Germanial year 3) " la mesure [républicaine] de superficie pour les terrains, égale à un carré de dix mètres de côté "". Le CIV (Centre d'Instruction de Vilgénis) – Forum des Anciens. Retrieved 2010-03-02.
- ↑ Adler. p. 106.Missing or empty
`|title=`

(help) - ↑ Adler. p. 269.Missing or empty
`|title=`

(help) - ↑ Denis Février. "Un historique du mètre" (in French). Ministère de l'Economie, des Finances et de l'Industrie. Retrieved 2011-03-10.
- ↑ Hallock, William; Wade, Herbert T (1906). "Outlines of the evolution of weights and measures and the metric system". London: The Macmillan Company. pp. 66–69.
- ↑ Adler. pp. 349–357.Missing or empty
`|title=`

(help) - ↑ Wolfgang Appell (2002). "Amtliche Maßeinheiten in Europa 1842" [Official units of measure in Europe 1842] (in German). ISBN 3-7686-1036-5 . Retrieved 2011-02-10Website based on
*Alte Meß und Währungssysteme aus dem deutschen Sprachgebiet* - ↑ "The Metre Convention". Bureau international des poids et mesures/International Bureau of Weights and Measures (BIPM). Retrieved 2011-02-13.
- ↑ FJ Smith (1973). "Standard Kilogram Weights: A Story of Precision Fabrication" (PDF).
*Platinum Metals Review*. Johnson Matthey.**17**(2): 66–68. Retrieved 2011-03-07. - ↑ "poncelet (physics)". The Free Dictionary by Farlex. Retrieved 2011-02-17.
- ↑ Thiery Thomasset, Universitié de Technology, Compiègne (December 2010). "Jean Victor Poncelet (1788-1867)" (PDF).
*Tout sur les unités de mesure*(in French). Archived from the original (PDF) on 2016-03-03. Retrieved 2011-02-17.CS1 maint: multiple names: authors list (link) - ↑ "Council Directive of 18 October 1971 on the approximation of laws of the member states relating to units of measurement, (71/354/EEC)" . Retrieved 2009-02-07.

This page is based on this Wikipedia article

Text is available under the CC BY-SA 4.0 license; additional terms may apply.

Images, videos and audio are available under their respective licenses.

Text is available under the CC BY-SA 4.0 license; additional terms may apply.

Images, videos and audio are available under their respective licenses.