Editing Metrication (section)

==Forerunners of metrication ==
[[File:Metric system French adoption decree (1795).jpg|thumb|upright=0.75|National Convention decree of April 1795 establishing the metric system]]

The metre was adopted as exclusive measure in 1801 under the [[French Consulate]], then the [[First French Empire]] until 1812, when [[Napoleon]] decreed the introduction of the ''[[mesures usuelles]]'' which remained in use in France up to 1840 in the reign of [[Louis Philippe I|Louis Philippe]].<ref>{{Cite book|last=Larousse|first=Pierre (1817-1875) Auteur du texte|url=https://gallica.bnf.fr/ark:/12148/bpt6k205363w|title=Grand dictionnaire universel du XIXe siècle : français, historique, géographique, mythologique, bibliographique.... T. 11 MEMO-O / par M. Pierre Larousse|date=1866–1877|pages=163|access-date=22 December 2021|archive-date=22 December 2021|archive-url=https://web.archive.org/web/20211222110248/https://gallica.bnf.fr/ark:/12148/bpt6k205363w|url-status=live}}</ref> Meanwhile, the metre was adopted by the Republic of Geneva.<ref name=":5" /> After the joining of [[canton of Geneva]] to Switzerland in 1815, [[Guillaume Henri Dufour]] published the first Swiss official map for which the metre was adopted as unit of length.<ref name=":6" /><ref name=":7" /> A Swiss-French binational officer, [[Napoleon III|Louis Napoléon Bonaparte]] was present when a baseline was measured near [[Zürich]] for [[Topographic Map of Switzerland|Dufour map]] which would win the gold medal for the national map at the [[Exposition Universelle (1855)|Exposition Universelle of 1855]].<ref>{{Cite book|last=Durand|first=Roger|url=https://books.google.com/books?id=7-8LnQ9iF04C|title=Guillaume-Henri Dufour dans son Temps 1787-1875|date=1991|publisher=Librairie Droz|isbn=978-2-600-05069-2|pages=145|language=fr}}</ref><ref>{{Cite web|title=Napoleon III.|url=https://hls-dhs-dss.ch/articles/023316/2010-11-02/|access-date=22 December 2021|website=hls-dhs-dss.ch|language=de|archive-date=14 December 2021|archive-url=https://web.archive.org/web/20211214074352/https://hls-dhs-dss.ch/articles/023316/2010-11-02/|url-status=live}}</ref><ref>{{Cite web|date=14 July 2019|title=Henri Dufour et la carte de la Suisse|url=https://blog.nationalmuseum.ch/fr/2019/07/dufour-le-cartographe/|access-date=22 December 2021|website=Musée national - Blog sur l'histoire suisse|language=fr-FR|archive-date=8 January 2022|archive-url=https://web.archive.org/web/20220108033346/https://blog.nationalmuseum.ch/fr/2019/07/dufour-le-cartographe/|url-status=live}}</ref> Among the scientific instruments calibrated on the metre, which were displayed at the Exposition Universelle, was [[Jean Brunner|Brunner]] apparatus, a geodetic instrument devised for measuring the central baseline of Spain whose designer, [[Carlos Ibáñez e Ibáñez de Ibero]] would represent Spain at the [[International Statistical Institute]]. In addition to the Exposition Universelle and the second Statistical Congress held in Paris, an International Association for obtaining a uniform decimal system of measures, weights, and coins was created there in 1855.<ref>{{Cite book|last=Quinn|first=T. J|url=|title=From artefacts to atoms: the BIPM and the search for ultimate measurement standards|date=2012|isbn=978-0-19-990991-9|pages=8|publisher=Oxford University Press |oclc=861693071}}</ref><ref>{{Cite book|last=Yates|first=James|url=https://play.google.com/store/books/details?id=mAo_AAAAYAAJ|title=Narrative of the Origin and Formation of the International Association for Obtaining a Uniform Decimal System of Measures, Weights and Coins|date=1856|publisher=Bell and Daldy|access-date=22 December 2021|archive-date=22 December 2021|archive-url=https://web.archive.org/web/20211222125411/https://play.google.com/store/books/details?id=mAo_AAAAYAAJ|url-status=live}}</ref><ref>{{Cite journal|last=Brenni|first=Paolo|date=1996|title=19th Century French Scientific Instrument Makers - XI: The Brunners and Paul Gautier|url=https://www.unav.es/gep/TheBrunnersCartaParis.pdf|journal=Bulletin of the Scientific Instrument Society|volume=49|pages=3–5|via=UNAV|access-date=22 December 2021|archive-date=18 September 2021|archive-url=https://web.archive.org/web/20210918062512/https://www.unav.es/gep/TheBrunnersCartaParis.pdf|url-status=live}}</ref><ref>{{cite journal |last1=Appell |first1=Paul |title=Le centenaire du général Ibañez de Ibéro |journal=Revue internationale de l'enseignement |date=1925 |volume=79 |issue=1 |pages=208–211 |url=https://education.persee.fr/doc/revin_1775-6014_1925_num_79_1_7841 |access-date=22 December 2021 |archive-date=16 December 2021 |archive-url=https://web.archive.org/web/20211216072326/https://education.persee.fr/doc/revin_1775-6014_1925_num_79_1_7841 |url-status=live }}</ref> Copies of the Spanish standard would be made for Egypt, France and Germany.<ref>{{Cite book |last=Tardi |first=Pierre |url=https://gallica.bnf.fr/ark:/12148/bpt6k3355272d |title=Traité de géodésie |date=1934 |pages=25 |author-link=Pierre Tardi |access-date=22 December 2021 |archive-date=18 December 2021 |archive-url=https://web.archive.org/web/20211218101406/https://gallica.bnf.fr/ark:/12148/bpt6k3355272d |url-status=live }}</ref><ref>{{Cite web|last=Zuerich|first=ETH-Bibliothek|title=Procès-verbaux des séances de la commission géodésique suisse|url=https://www.e-periodica.ch//digbib/view?pid=bsn-001%3A1877%3A11%3A%3A853|url-status=dead|access-date=22 December 2021|website=E-Periodica|pages=14, 18|language=fr|archive-date=29 July 2021|archive-url=https://web.archive.org/web/20210729085259/https://www.e-periodica.ch//digbib/view?pid=bsn-001:1877:11::853}}</ref> These standards were compared to each other and with Borda apparatus which was the main reference for measuring all geodetic baselines in France.<ref>{{Cite book|last=texte|first=Ismāʿīl-Afandī Muṣṭafá (1825-1901) Auteur du|url=https://gallica.bnf.fr/ark:/12148/bpt6k62478474|title=Recherche des coefficients de dilatation et étalonnage de l'appareil à mesurer les bases géodésiques appartenant au gouvernement égyptien / par Ismaïl-Effendi-Moustapha, ...|date=1864|access-date=22 December 2021|archive-date=18 December 2021|archive-url=https://web.archive.org/web/20211218101418/https://gallica.bnf.fr/ark:/12148/bpt6k62478474|url-status=live}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=uiwPAAAAQAAJ&q=Exp%C3%A9riences+faites+avec+l'appareil+%C3%A0+mesurer+les+bases+appertant+%C3%A0+la+commission+de+la+carte+d'Espagne|title=Expériences faites avec l'appareil à mesurer les bases appertant à la commission de la carte d'Espagne /: ouvrage publié par ordre de la reine|date=1860|publisher=J. Dumaine|language=fr}}</ref><ref name=":8">{{cite journal |last1=Soler |first1=T. |title=A profile of General Carlos Ibáñez e Ibáñez de Ibero: first president of the International Geodetic Association |journal=Journal of Geodesy |date=10 February 1997 |volume=71 |issue=3 |pages=176–188 |doi=10.1007/s001900050086 |bibcode=1997JGeod..71..176S |s2cid=119447198}}</ref> These comparisons were essential, because of the [[Thermal expansion|expansibility]] of solid materials with raise in temperature. Indeed, one fact had constantly dominated all the fluctuations of ideas on the measurement of geodesic bases: it was the constant concern to accurately assess the temperature of standards in the field; and the determination of this variable, on which depended the length of the instrument of measurement, had always been considered by [[Geodesy|geodesists]] as so difficult and so important that one could almost say that the history of measuring instruments is almost identical with that of the precautions taken to avoid temperature errors.<ref>{{cite journal |last1=Guillaume |first1=Ch.-Ed |title=La mesure rapide des bases géodésiques |journal=Journal de Physique Théorique et Appliquée |date=1906 |volume=5 |issue=1 |pages=242–263 |doi=10.1051/jphystap:019060050024200 |url=https://zenodo.org/record/2007289 |access-date=9 December 2023 |archive-date=6 October 2023 |archive-url=https://web.archive.org/web/20231006212819/https://zenodo.org/record/2007289 |url-status=live }}</ref> In 1867, the second general Conference of the [[International Association of Geodesy|European Arc Measurement]] recommended the adoption of the metre in replacement of the toise. In 1869, the [[Russian Academy of Sciences|Saint Petersburg Academy of Sciences]] sent to the [[French Academy of Sciences]] a report drafted by [[Otto Wilhelm von Struve]], [[Heinrich von Wild]] and [[Moritz von Jacobi]] inviting his French counterpart to undertake joint action with a view to ensuring the universal use of the [[metric system]] in all scientific work.<ref>{{cite journal |last1=Guillaume |first1=Ed. |title=Le Systeme Metrique est-il en Peril? |journal=L'Astronomie |date=1916 |volume=30 |pages=242–249 |bibcode=1916LAstr..30..242G}}</ref> The same year, Napoleon III convened the International Metre Commission which was to meet in Paris in 1870. The [[Franco-Prussian War]] broke out, the [[Second French Empire]] collapsed, but the metre survived.<ref>{{cite book |last1=Boucheron |first1=Patrick |last2=Delalande |first2=Nicolas |last3=Mazel |first3=Florian |last4=Potin |first4=Yann |last5=Singaravélou |first5=Pierre |title=Histoire mondiale de la France |date=2018 |publisher=Éditions Points |isbn=978-2-7578-7442-4 |page=694 |oclc=1057452808}}</ref><ref>{{cite journal |last1=Quinn |first1=Terry |title=Wilhelm Foerster's Role in the Metre Convention of 1875 and in the Early Years of the International Committee for Weights and Measures |journal=Annalen der Physik |date=May 2019 |volume=531 |issue=5 |doi=10.1002/andp.201800355 |bibcode=2019AnP...53100355Q |s2cid=125240402 |doi-access=free}}</ref>

During the nineteenth century the metric system of weights and measures proved a convenient political compromise during the unification processes in the Netherlands, Germany and Italy. In 1814, Portugal became the second country not part of the French Empire to officially adopt the metric system. Spain found it expedient in 1849 to follow the French example and within a decade [[Latin America]] had also adopted the metric system, or had already adopted the system, such as the case of Chile by 1848. There was considerable resistance to metrication in the United Kingdom and in the United States. Despite this, they were actually the first countries in the World to use a metric standard for cartography.<ref name=":2" /><ref name=":3" /><ref>{{Cite book |last=texte |first=Ismāʿīl-Afandī Muṣṭafá (1825-1901) Auteur du |url=https://gallica.bnf.fr/ark:/12148/bpt6k62478474 |title=Recherche des coefficients de dilatation et étalonnage de l'appareil à mesurer les bases géodésiques appartenant au gouvernement égyptien / par Ismaïl-Effendi-Moustapha, ... |date=1864}}</ref><ref name=":8" /><ref>{{Cite news |title=Nomination of the STRUVE GEODETIC ARC for inscription on the WORLD HERITAGE LIST |pages=40, 143–144 |url=https://whc.unesco.org/uploads/nominations/1187.pdf |access-date=7 October 2023 |archive-date=19 October 2015 |archive-url=https://web.archive.org/web/20151019205752/https://whc.unesco.org/uploads/nominations/1187.pdf |url-status=live }}</ref>

===France (1795–1840)===
The introduction of the metric system into France in 1795 was done on a district by district basis with Paris being the first district. By modern standards the transition was poorly managed. Although thousands of pamphlets were distributed, the Agency of Weights and Measures who 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, they only had 25,000 in store.<ref name="Alder">{{cite book |last=Alder |first=Ken |title=The Measure of all Things – The Seven-Year-Odyssey that Transformed the World |publisher=Abacus |year=2002 |isbn=978-0-349-11507-8 |location=London}}</ref>{{rp| 269}} This, combined with the excesses of the Revolution and the high level of illiteracy in 18th century France, made the metric system unpopular.

[[Napoleon]] himself ridiculed the metric system but, as an able administrator, recognised the value of a sound basis for a system of measurement. Under the {{lang|FR|décret impérial du 12 février 1812}} (imperial decree of 12 February 1812), a new system of measure – the {{lang|FR|[[mesures usuelles]]}} ("customary measures") was introduced for use in small retail businesses – 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.<ref name="Fevier">{{cite web
|url = http://www.industrie.gouv.fr/metro/aquoisert/metre.htm
|title = Un historique du mètre
|language = fr
|author = Denis Février
|publisher = {{lang|FR|Ministère de l'Economie, des Finances et de l'Industrie}}
|access-date = 10 March 2011
|archive-date = 28 February 2011
|archive-url = https://web.archive.org/web/20110228185545/http://www.industrie.gouv.fr/metro/aquoisert/metre.htm
|url-status = live
}}</ref> That system reintroduced the names of many units used during the ancient regime, but their values were redefined in terms of metric units. Thus the {{lang|FR|toise}} was defined as being two metres, with six {{lang|FR|pieds}} making up one ''toise'', twelve {{lang|FR|pouces}} making up one ''pied'' and twelve {{lang|FR|lignes}} making up one ''pouce''. Likewise the {{lang|FR|livre}} was defined as being 500&nbsp;g, each ''livre'' comprising sixteen ''once'' and each ''once'' eight ''gros'' and the ''aune'' as 120 centimetres.<ref name="H&H">{{cite web
|url = https://archive.org/stream/outlinesofevolut00halluoft/outlinesofevolut00halluoft_djvu.txt
|title = Outlines of the evolution of weights and measures and the metric system
|first1 = William
|last1 = Hallock
|first2 = Herbert T
|last2 = Wade
|publisher = The Macmillan Company
|year = 1906
|pages = 66–69
|location = London}}</ref> This intermediate step eased the transition to a metric-based system.

By the {{lang|FR|Loi du 4 juillet 1837}} (the law of 4 July 1837), [[Louis Philippe I]]  effectively revoked the use of ''mesures usuelles'' by reaffirming the laws of measurement of 1795 and 1799 to be used from 1 May 1840.<ref name="histmet">{{cite web
| url        = http://www.french-metrology.com/en/history/history-mesurement.asp
| title        = History of measurement
| publisher        = Laboratoire national de métrologie et d'essais (LNE) (Métrologie française)
| access-date        = 6 February 2011
| archive-date        = 25 April 2011
| archive-url        = https://web.archive.org/web/20110425025041/http://www.french-metrology.com/en/history/history-mesurement.asp
| url-status        = dead
}}</ref><ref name="crease">{{cite book |first=Robert P. |last=Crease |title=World in the Balance: The Historical Quest for an Absolute System of Measurement |year=2011 |publisher=W. W. Norton & Company |location= New York & London |isbn=978-0-393-34354-0 |pages=124 & 164}}</ref> However, many units of measure, such as the ''livre'' (for half a kilogram), remained in everyday use for many years,<ref name="crease"/><ref>Crease (2011) refers to: {{cite book |last=Kennelly |first=Arthur E. |title=Vestiges of Pre-metric Weights and Measures Persisting in Metric-system Europe, 1926–27 |location=New York |publisher=Macmillan |year=1928 |page=vii}}</ref> and to a residual extent up to this day.
[[File:Fußmaße1.jpg|upright=0.75|thumb|Conversion table in an 1848 German schoolbook showing the metric equivalent of the foot in use in over two dozen countries, including several German states]]

===Germany (1810–1877)===
[[File:Baeyer.jpg|left|thumb|upright=0.75|Johann Jacob Baeyer, founder of the ''[[International Association of Geodesy|Europäische Gradmessung]]''|278x278px]]
[[File:Alter Grenzstein Pontebba 01.jpg|upright=0.75|thumb|Stone marking the [[Austria-Hungary|Austro-Hungarian]]/Italian border at [[Pontebba]] displaying [[myriametre]]s (10&nbsp;km), a unit used in [[Central Europe]] in the 19th century<ref name=Europa1842/>]]
At the outbreak of the French Revolution, much of modern-day Germany and Austria were part of the [[Holy Roman Empire]] which had become a loose federation of kingdoms, principalities, free cities, bishoprics and other fiefdoms, each with its own system of measurement, though in most cases the systems were loosely derived from the [[Carolingian]] system instituted by [[Charlemagne]] a thousand years earlier.

During the Napoleonic era, some of the German states moved to reform their systems of measurement using the prototype metre and kilogram as the basis of the new units. [[Baden]], in 1810, for example, redefined the ''Ruthe'' (rods) as being 3.0&nbsp;m exactly and defined the subunits of the ''Ruthe'' as 1 ''Ruthe'' = 10&nbsp;''Fuß'' (feet) = 100&nbsp;''Zoll'' (inches) = 1,000&nbsp;''Linie'' (lines) = 10,000&nbsp;''Punkt'' (points) (for simplicity at the expense of grammar, these are the singular forms of each name) while the ''Pfund'' was defined as 500&nbsp;g, divided into 30&nbsp;Loth, each of 16.67&nbsp;g.<ref name="Europa1842">{{cite web
|url = http://home.fonline.de/fo0126//geschichte/groessen/mas1.htm
|title = Amtliche Maßeinheiten in Europa 1842
|language = de
|trans-title = Official units of measure in Europe 1842
|access-date = 26 March 2011
|archive-date = 14 October 2011
|archive-url = https://web.archive.org/web/20111014224232/http://home.fonline.de/fo0126//geschichte/groessen/mas1.htm
|url-status = live
}} Text version of Malaisé's book.</ref><ref>{{cite book
|url = http://home.fonline.de/rs-ebs/geschichte/buch/titel.htm
|title = Theoretisch-practischer Unterricht im Rechnen
|language = de
|trans-title = Theoretical and practical instruction in arithmetic
|author = Ferdinand Malaisé
|place = München
|year = 1842
|pages = 307–322
|access-date = 26 March 2011
|archive-date = 14 October 2011
|archive-url = https://web.archive.org/web/20111014221605/http://home.fonline.de/rs-ebs/geschichte/buch/titel.htm
|url-status = live
}}</ref> [[Bavaria]], in its reform of 1811, trimmed the Bavarian ''Pfund'' from 561.288&nbsp;g to 560&nbsp;g exactly, consisting of 32 ''Loth'', each of 17.5&nbsp;g<ref>{{cite web
|url = http://www.digitalis.uni-koeln.de/Grebenau/grebenau_index.html
|title = Tabellen zur Umwandlung des bayerischen Masses und Gewichtes in metrisches Maß und Gewicht und umgekehrt
|language = de
|trans-title = Conversion tables for converting between Bavarian units of measure and metric units
|location = Munich
|author = Heinrich Grebenau
|year = 1870
|access-date = 7 March 2011
|archive-date = 22 January 2011
|archive-url = https://web.archive.org/web/20110122043300/http://www.digitalis.uni-koeln.de/Grebenau/grebenau_index.html
|url-status = live
}}</ref> while the [[Prussia]]n ''Pfund'' remained at 467.711&nbsp;g.<ref>{{Cite thesis
|degree= Dr.&nbsp;med.&nbsp;vet
|pages= 14–20
|title= Der Marstall des Schlosses Anholt (16. bis 18. Jahrhundert) – Quellen und Materialien zur Geschichte der Pferdehaltung im Münsterland
|trans-title= The stables of the castle Anholt (16th to 18th century) – sources and materials on the history of horses in Munster
|language= de
|url= http://elib.tiho-hannover.de/dissertations/parrass_ss06.pdf
|author= Silke Parras
|year= 2006
|publisher= Tierärztliche Hochschule Hannover [Hannover veterinary university]
|access-date= 7 March 2011
|archive-date= 19 July 2011
|archive-url= https://web.archive.org/web/20110719093650/http://elib.tiho-hannover.de/dissertations/parrass_ss06.pdf
|url-status= live
}}</ref>

After the [[Congress of Vienna]] there was a degree of commercial cooperation between the various German states resulting in the German Customs Union (''[[Zollverein]]''). There were, however, still many barriers to trade until [[Bavaria]] took the lead in establishing the General German Commercial Code in 1856. As part of the code the ''Zollverein'' introduced the ''[[Zollpfund]]'' (Customs Pound) which was defined as exactly 500&nbsp;g and could be split into 30&nbsp;'lot'.<ref name="Zollmuseum">{{cite book
|url = https://books.google.com/books?id=vnwuk-LpMGkC&q=zollpfund+30+lot+1854&pg=PA129
|title = Die Mass-und Gewichtsreformen in Deutschland im 19. Jahrhundert unter besonderer Berucksichtigung der Rolle Carl August Steinheils und der Bayerischen Akademie der Wissenschaften
|trans-title=The weights and measure reforms in Germany in the 19th century with special reference to Rolle Carl August and the Bavarian Academy of Sciences 
|first1 = Cornelia 
|last1 = Meyer-Stoll
|page = 129
|isbn = 978-3-7696-0124-4
|publisher = Bayerischen Akademie der Wissenschaften [Bavarian Academy of Sciences]
|language = de
|location = Munich
|year = 2010}}</ref> This unit was used for inter-state movement of goods, but was not applied in all states for internal use.

In 1832, [[Carl Friedrich Gauss]] studied the [[Earth's magnetic field]] and proposed adding the [[second]] to the basic units of the [[metre]] and the [[kilogram]] in the form of the [[Centimetre–gram–second system of units|CGS system]] ([[centimetre]], [[gram]], second). In 1836, he founded the ''Magnetischer Verein'', the first international scientific association, in collaboration with [[Alexander von Humboldt]] and [[Wilhelm Eduard Weber|Wilhelm Edouard Weber]]. [[Geophysics]] (the study of the Earth by the means of [[physics]]) preceded physics{{citation needed|date=November 2023}} and contributed to the development of its methods. It was primarily a [[natural philosophy]] whose object was the study of natural phenomena such as the Earth's magnetic field, [[lightning]] and [[gravity]]. The coordination of the observation of geophysical phenomena in different points of the globe was of paramount importance and was at the origin of the creation of the first international scientific associations. The foundation of the ''Magnetischer Verein'' would be followed by that of the Central European Arc Measurement (German: [[International Association of Geodesy|''Mitteleuropäische Gradmessung'']]) on the initiative of [[Johann Jacob Baeyer]] in 1863, and by that of the [[World Meteorological Organization|International Meteorological Organisation]] whose second president, the Swiss [[meteorologist]] and [[physicist]], [[Heinrich von Wild]] represented [[Russian Empire|Russia]] at the [[General Conference on Weights and Measures|International Committee for Weights and Measures]] (CIPM).<ref>{{Cite web|date=8 December 2015|title=History of IMO|url=https://public-old.wmo.int/en/about-us/who-we-are/history-IMO|archive-url=https://web.archive.org/web/20231218170901/https://public-old.wmo.int/en/about-us/who-we-are/history-IMO|url-status=dead|archive-date=18 December 2023|access-date=7 January 2021|website=World Meteorological Organization}}</ref><ref name=":4">{{Cite web|title=Wild, Heinrich|url=https://hls-dhs-dss.ch/articles/028982/2014-11-11/|access-date=7 January 2021|website=hls-dhs-dss.ch|language=de}}</ref><ref>{{Cite web|last=|first=|date=1903|title=Heinrich Von Wild (1833-1902) in Comlté International Des Poids Et Mesures. Procès-Verbaux Des Séances. Deuxième Série. Tome Ii. Session De 1903.|url=https://www.bipm.org/utils/common/pdf/obituaries/1903_CIPM_CH&RU_WILD-Heinrich.pdf|url-status=dead|archive-url=https://web.archive.org/web/20210124084245/https://www.bipm.org/utils/common/pdf/obituaries/1903_CIPM_CH%26RU_WILD-Heinrich.pdf|archive-date=24 January 2021|access-date=|website=BIPM}}</ref> In 1867, the European Arc Measurement (German: ''[[International Association of Geodesy|Europäische Gradmessung]]'') called for the creation of a new, ''international prototype metre'' (IPM) and the arrangement of a system where national standards could be compared with it. The French government gave practical support to the creation of an International Metre Commission, which met in Paris in 1870 and again in 1872 with the participation of about thirty countries. The [[Metre Convention]] was signed on 20 May 1875 in Paris and the [[International Bureau of Weights and Measures]] was created under the supervision of the [[International Committee for Weights and Measures|CIPM]].

Although the Zollverein collapsed after the [[Austro-Prussian War]] of 1866, the metric system became the official system of measurement in the newly formed [[German Empire]] in 1872<ref name=Alder/>{{rp|350}} and of Austria in 1875.<ref name="PopularScience">{{cite journal
|journal = Popular Science Monthly
|url = https://books.google.com/books?id=IyUDAAAAMBAJ&q=The+Metric+System+-+Shall+it+be+compulsory&pg=PA394
|title = The Metric System – Shall it be compulsory?
|author = W Leconte Stephens
|date = March 1904
|pages = 394–405
|access-date = 17 May 2011}}</ref> The Zollpfund ceased to be legal in Germany after 1877.<ref>{{cite web
|url = http://universal_lexikon.deacademic.com/3160/Pfund
|title = Pfund
|publisher = Universal-Lexikon
|access-date = 17 May 2011
|year = 2010
|language = de
|archive-date = 6 September 2014
|archive-url = https://web.archive.org/web/20140906091848/http://universal_lexikon.deacademic.com/3160/Pfund
|url-status = dead
}}</ref>

===Italy (1797–1870)===
[[File:Vicopisano-misure antiche.jpg|thumb|upright=0.75|Tablet showing conversions of legacy units of weights and measures to metric units, [[Vicopisano]], [[Tuscany]]]]
The [[Cisalpine Republic]], a North Italian republic set up by Napoleon in 1797 with its capital at [[Milan]], first adopted a modified form of the metric system based on the ''braccio cisalpino'' (Cisalpine cubit) which was defined to be half a metre.<ref name="metricItaly">{{cite web
|url = http://www.2iceshs.cyfronet.pl/2ICESHS_Proceedings/Chapter_16/R-8_Borgato.pdf
|title = The first applications of the metric system in Italy
|author = Maria Teresa Borgato
|work = The Global and the Local:The History of Science and the Cultural Integration of Europe. Proceedings of the 2nd ICESHS
|location = Cracow, Poland
|date = 6–9 September 2006
|publisher = The Press of the Polish Academy of Arts and Sciences
|access-date = 17 March 2011
|archive-date = 6 November 2020
|archive-url = https://web.archive.org/web/20201106070022/http://www.2iceshs.cyfronet.pl/2ICESHS_Proceedings/Chapter_16/R-8_Borgato.pdf
|url-status = dead
}}</ref> In 1802 the Cisalpine Republic was renamed the [[Italian Republic (Napoleonic)|Italian Republic]], with Napoleon as its head of state. The following year the Cisalpine system of measure was replaced by the metric system.<ref name = metricItaly/>

In 1806, the Italian Republic was replaced by the [[Kingdom of Italy (Napoleonic)|Kingdom of Italy]] with Napoleon as its emperor. By 1812, all of Italy from Rome northwards was under the control of Napoleon, either as French Departments or as part of the Kingdom of Italy, ensuring that the metric system was in use throughout this region.

After the [[Congress of Vienna]], the various Italian states reverted to their original systems of measurements, but in 1845 the [[Kingdom of Sardinia (1720–1861)|Kingdom of Piedmont and Sardinia]] passed legislation to introduce the metric system within five years. By 1860, most of Italy had been unified under the King of Sardinia [[Victor Emmanuel II]]; and under ''Law 132 of 28 July 1861'' the metric system became the official system of measurement throughout the kingdom. Numerous ''Tavole di ragguaglio'' (conversion tables) were displayed in shops until 31 December 1870.<ref name = metricItaly/>

===Netherlands (1799–1817)===
The Netherlands (as the revolutionary [[Batavian Republic]]) began to use the metric system from 1799 but, as with its co-revolutionaries in France, encountered [[Mesures usuelles#Rationale behind the new system|numerous practical difficulties]]. Subsequently, as part of the [[First French Empire]] since 1809, the Netherlands used Napoleon's {{lang|FR|[[mesures usuelles]]}} from their introduction in 1812 until the fall of his Empire in 1815. Under the (Dutch) [[Weights and Measures Act]] of 21 August 1816 and the Royal decree of 27 March 1817 ({{lang|NL|Koningklijk besluit van den 27 Maart 1817}}), the newly formed [[Kingdom of the Netherlands]] abandoned the {{lang|FR|mesures usuelles}} in favour of the "Dutch" [[metric system]] ({{lang|NL|Nederlands metrisch stelsel}}) in which metric units were simply given the names of units of measure that were then in use: for instance the {{lang|NL|ons}} (ounce) was defined as 100&nbsp;g.<ref>{{cite book
|url = https://archive.org/details/allereerstegron00ramagoog
|title = Allereerste Gronden der Cijferkunst
|author = Jacob de Gelder
|location = 's Gravenhage and Amsterdam
|language = nl
|year = 1824
|pages = [https://archive.org/details/allereerstegron00ramagoog/page/n364 155]–157
|publisher = de Gebroeders van Cleef
|trans-title=Introduction to Numeracy
|access-date = 2 March 2011}}</ref>

=== Norway (1875)===
In 1875, Norway was the first country to ratify the metre convention, and it was seen as an important step towards Norwegian independence. The decision to adopt the metric system is said to have been [[Norwegian Parliament's adoption of the metric system|the Norwegian Parliament's fastest decision]] in peacetime.

===Portugal (1814)===
In August 1814, Portugal officially adopted the metric system but with the names of the units substituted by [[Portuguese customary units|Portuguese traditional ones]]. In this system the basic units were the ''mão-travessa'' (hand) = 1&nbsp;[[decimetre]] (10&nbsp;''mão-travessas'' = 1&nbsp;''vara'' (yard) = 1&nbsp;metre), the ''[[canada (unit)|canada]]'' = 1&nbsp;litre and the ''libra'' (pound) = 1&nbsp;kilogram.<ref name="Fatima">{{cite web |author1=Fátima Paixão |author2=Fátima Regina Jorge |date=2006 |title=''Success and constraints in adoption of the metric system in Portugal'' |url=http://www.2iceshs.cyfronet.pl/2ICESHS_Proceedings/Chapter_16/R-8_Paixao_Jorge.pdf |url-status=bot: unknown |archive-url=https://web.archive.org/web/20131203032144/http://www.2iceshs.cyfronet.pl/2ICESHS_Proceedings/Chapter_16/R-8_Paixao_Jorge.pdf |archive-date=3 December 2013 |access-date=21 September 2022 |publisher=The Global and the Local: History of Science and the Cultural Integration of Europe}}</ref>

===Spain (1700–1889)===
[[File:General Carlos Ibáñez e Ibáñez de Ibero.jpg|thumb|upright=0.75|Don Carlos Ibáñez e Ibáñez de Ibero, first president of the [[International Association of Geodesy|International Geodetic Association]] and of the [[General Conference on Weights and Measures|International Committee for Weights and Measures]]|left]]
Until the ascent of the [[House of Bourbon|Bourbon]] monarchy in Spain in 1700, each region of Spain had its own system of measurement. The new Bourbon monarchy tried to centralise control and with it the system of measurement. There were debates regarding the desirability of retaining the [[Kingdom of Castile|Castilian]] units of measure or, in the interests of harmonisation, adopting the French system.<ref name="metricSpain">{{cite web
|url = http://www.2iceshs.cyfronet.pl/2ICESHS_Proceedings/Chapter_16/R-8_Navarro_Merino.pdf
|title = The units of length in the Spanish treatises of military engineering
|first1 = Juan Navarro
|last1 = Loidi
|first2 = Pilar Merino
|last2 = Saenz
|work = The Global and the Local: The History of Science and the Cultural Integration of Europe. Proceedings of the 2nd ICESHS
|location = Cracow, Poland
|date = 6–9 September 2006
|publisher = The Press of the Polish Academy of Arts and Sciences
|access-date = 17 March 2011
|archive-date = 3 October 2011
|archive-url = https://web.archive.org/web/20111003220229/http://www.2iceshs.cyfronet.pl/2ICESHS_Proceedings/Chapter_16/R-8_Navarro_Merino.pdf
|url-status = dead
}}</ref> Although Spain assisted [[Pierre Méchain|Méchain]] in his meridian survey, the Government feared the French revolutionary movement and reinforced the Castilian units of measure to counter such movements. By 1849 however, it proved difficult to maintain the old system and in that year the metric system became the legal system of measure in Spain.<ref name = metricSpain/>

The [[Spanish Royal Academy of Sciences|Spanish Royal Academy of Science]] urged the Government to approve the creation of a large-scale map of [[Spain]] in 1852. The following year [[Carlos Ibáñez e Ibáñez de Ibero]] was appointed to undertake this task. All the scientific and technical material had to be created. Ibáñez e Ibáñez de Ibero and Saavedra went to [[Paris]] to supervise the production by Brunner of a measuring instrument which they had devised and which they later compared with [[Jean-Charles de Borda|Borda]]'s double-toise N°1 which was the main reference for measuring all geodetic bases in France and whose length was by definition 3.8980732 metres at a specified temperature.<ref name=":2" /><ref>{{Cite book|last1=Delambre|first1=Jean-Baptiste (1749-1822) Auteur du texte|url=https://gallica.bnf.fr/ark:/12148/bpt6k1106055|title=Base du système métrique décimal, ou Mesure de l'arc du méridien compris entre les parallèles de Dunkerque et Barcelone. T. 3 /, exécutée en 1792 et années suivantes, par MM. Méchain et Delambre, rédigée par M. Delambre,...|last2=Méchain|first2=Pierre (1744-1804) Auteur du texte|date=1806–1810|publisher=|isbn=|location=|pages=139, 228|access-date=5 January 2021|archive-date=9 January 2021|archive-url=https://web.archive.org/web/20210109172924/https://gallica.bnf.fr/ark:/12148/bpt6k1106055|url-status=live}}</ref>

In 1865 the triangulation of [[Spain]] was connected with that of [[Portugal]] and [[France]]. In 1866 at the conference of the Association of Geodesy in [[Neuchâtel]], Ibáñez announced that [[Spain]] would collaborate in remeasuring the [[Paris meridian|French meridian arc]]. In 1879 Ibáñez and [[François Perrier (French Army officer)|François Perrier]] (representing France) completed the junction between the geodetic network of Spain and [[French Algeria|Algeria]] and thus completed the measurement of the [[Paris meridian|French meridian arc]] which extended from [[Shetland]] to the [[Sahara]].

In 1866, Spain and Portugal joined the Central European Arc Measurement which would become the [[International Association of Geodesy|European Arc Measurement]] the next year. In 1867 at the second general conference of the geodetic association held in Berlin, the question of an international standard unit of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth. The conference proposed according to recommendations drawn up by a committee chaired by [[Otto Wilhelm von Struve]] director of the [[Pulkovo Observatory]] in St. Petersburg the adoption of the [[metre]] and the creation of an international metre commission, after a preliminary discussion held in Neuchâtel between [[Johann Jacob Baeyer]] director of the Royal Prussian Geodetic Institute, [[Adolphe Hirsch]] founder of the [[Neuchâtel Observatory]] and [[Carlos Ibáñez e Ibáñez de Ibero]] Spanish representative, founder and first director of the [[Instituto Geográfico Nacional (Spain)|Instituto Geográfico Nacional]].<ref>{{Cite book|last=|first=|url=http://gfzpublic.gfz-potsdam.de/pubman/item/escidoc:108187:4/component/escidoc:272449/Generalbericht.mitteleurop%C3%A4ische.Gradmessung%201867.pdf|title=Bericht über die Verhandlungen der vom 30. September bis 7. October 1867 zu BERLIN abgehaltenen allgemeinen Conferenz der Europäischen Gradmessung.|publisher=Central Bureau der Europäischer Gradmessung|year=1868|isbn=|location=Berlin|pages=14. 123–134}}</ref><ref>{{cite journal |last1=Débarbat |first1=Suzanne |last2=Quinn |first2=Terry |title=Les origines du système métrique en France et la Convention du mètre de 1875, qui a ouvert la voie au Système international d'unités et à sa révision de 2018 |journal=Comptes Rendus Physique |date=January 2019 |volume=20 |issue=1–2 |pages=6–21 |doi=10.1016/j.crhy.2018.12.002 |doi-access=free |bibcode=2019CRPhy..20....6D}}</ref><ref>{{Cite web|last=Hirsch|first=Adolphe|date=1891|title=Don Carlos IBANEZ (1825-1891)|url=https://www.bipm.org/utils/common/pdf/obituaries/1891_CIPM_ES_IBANEZ-Don-Carlos.pdf|url-status=dead|archive-url=https://web.archive.org/web/20201026082704/https://www.bipm.org/utils/common/pdf/obituaries/1891_CIPM_ES_IBANEZ-Don-Carlos.pdf|archive-date=26 October 2020|access-date=|website=BIPM|pages=8–9}}</ref><ref>{{cite journal |last1=Drewes |first1=Hermann |last2=Kuglitsch |first2=Franz |last3=Adám |first3=József |last4=Rózsa |first4=Szabolcs |title=The Geodesist's Handbook 2016 |journal=Journal of Geodesy |date=October 2016 |volume=90 |issue=10 |pages=907–1205 |doi=10.1007/s00190-016-0948-z |bibcode=2016JGeod..90..907D |s2cid=125925505 |url=https://gfzpublic.gfz-potsdam.de/pubman/item/item_1981910_3/component/file_1985890/1981910.pdf}}</ref><ref>{{Cite web|last=Nacional|first=Instituto Geográfico|date=|title=Instituto Geográfico Nacional|url=https://www.ign.es/web/ign/portal/qsm-nuestra-historia|access-date=7 January 2021|website=Geoportal oficial del Instituto Geográfico Nacional de España|language=es-ES|archive-date=16 January 2021|archive-url=https://web.archive.org/web/20210116023805/https://www.ign.es/web/ign/portal/qsm-nuestra-historia|url-status=live}}</ref>
In November 1869 the French government issued invitations to join this commission. Spain accepted and [[Carlos Ibáñez e Ibáñez de Ibero]] took part in the Committee of preparatory research from the first meeting of the International Metre Commission in 1870. He became president of the permanent Committee of the International Metre Commission in 1872. In 1874 he was elected as president of the Permanent Commission of the [[International Association of Geodesy|European Arc Measurement]]. He also presided the General Conference of the [[International Association of Geodesy|European Arc Measurement]] held in Paris in 1875, when the association decided the creation of an international geodetic standard for the bases' measurement.<ref>{{Cite book|url=http://gallica.bnf.fr/ark:/12148/bpt6k949666|title=Histoire abrégée de l'astronomie / par Ernest Lebon,...|last=Lebon|first=Ernest (1846–1922) Auteur du texte|date=1899|publisher=Gauthier-Villars|location=Paris|pages=171|access-date=12 January 2018|archive-date=24 August 2017|archive-url=https://web.archive.org/web/20170824140556/http://gallica.bnf.fr/ark:/12148/bpt6k949666|url-status=live}}</ref> He represented Spain at the 1875 conference of the [[Metre Convention]], which was ratified the same year in Paris. The Spanish geodesist was elected as the first president of the [[International Committee for Weights and Measures]]. His activities resulted in the distribution of a platinum and iridium prototype of the [[metre]] to all States parties to the [[Metre Convention]] during the first meeting of the [[General Conference on Weights and Measures]] in 1889. These prototypes defined the metre right up until 1960.[[File:Bulletin de la Soci neuchloise des sciences naturelles (1898-) (20409300876).jpg|thumb|upright=0.75|Adolphe Hirsch, secretary of the [[International Association of Geodesy|International Geodetic Association]] and of the [[General Conference on Weights and Measures|International Committee for Weights and Measures]]]]

=== Switzerland (1801–1877)===
[[File:Guillaume-Henri Dufour.jpg|left|thumb|upright=0.75|Guillaume Henri Dufour, founder of [[Swisstopo]]]]
[[File:Heinrich Wild.jpg|thumb|upright=0.75|Heinrich von Wild, president of the [[International Meteorological Organization]] and member of the [[General Conference on Weights and Measures|International Committee for Weights and Measures]]]]
In 1801, the [[Helvetic Republic]] at the instigation of [[Johann Georg Tralles]] promulgated a law introducing the metric system. However this was never applied, because in 1803 the competence for weights and measures returned to the [[Cantons of Switzerland|cantons]]. On the territory of the current [[canton of Jura]], then annexed to France ([[Mont-Terrible]]), the metre was adopted in 1800. The [[Canton of Geneva]] adopted the metric system in 1813, the [[canton of Vaud]] in 1822, the [[canton of Valais]] in 1824 and the [[canton of Neuchâtel]] in 1857. In 1835, twelve cantons of the [[Swiss Plateau]] and the north-east adopted a concordat based on the federal foot (exactly 0.3 m) which entered into force in 1836. The cantons of [[Central Switzerland|central]] and [[eastern Switzerland]], as well as the Alpine cantons, continued to use the old measures.<ref name=":5">{{Cite web|title=Système métrique|url=https://hls-dhs-dss.ch/articles/013754/2014-05-22/|access-date=8 January 2021|website=hls-dhs-dss.ch|language=fr|archive-date=10 January 2021|archive-url=https://web.archive.org/web/20210110034838/https://hls-dhs-dss.ch/articles/013754/2014-05-22/|url-status=live}}</ref><ref>{{Cite web|title=Journal de Genève - 22.03.1854 - Page 1|url=https://www.letempsarchives.ch/page/JDG_1854_03_22/1/article/5203313|access-date=24 February 2021|website=www.letempsarchives.ch|archive-date=7 November 2023|archive-url=https://web.archive.org/web/20231107040659/https://www.letempsarchives.ch/page/JDG_1854_03_22/1/article/5203313|url-status=live}}</ref>

[[Guillaume Henri Dufour|Guillaume-Henri Dufour]] founded in 1838 in [[Geneva]] a topographic office (the future [[Swisstopo|Federal Office of topography]]), which published under his direction, from 1845 to 1864, the first official [[Topographic Map of Switzerland|map of Switzerland]], on the basis of new cantonal measurements. This map at [[Scale (map)|1:100,000]] engraved on copper, suggested the relief by hatching and shadows. The map projection adopted by the commission was the [[Bonne projection]], centred on the [[Bern]] Observatory (5° 6<nowiki>' 10.8''</nowiki> east of [[Paris meridian]]), although this point was much closer to the western end of Switzerland than to its eastern end. But its position was well known, and there was no more central [[observatory]]. The scale was set at 1:100 000 because it was considered more suitable for a country as rugged as Switzerland than the 1:80 000 adopted for the large [[Geography of France|map of France]] and the two maps were in any case inconsistent, as the meridians of the [[Cartography of Switzerland|map of Switzerland]] tilted in the opposite direction to those of the map of France. The map commission wanted to adopt decimal measures; and Switzerland did not have an already existing map which, like the [[Cassini map]], used a scale close to 1:86 400, i.e. 1 [[line (unit)|line]] ({{frac|1|12}} of a French inch) to 100 [[toise]]s (i.e. 600 French feet). The [[metre]] was adopted as a linear measure, and the entire map was divided into twenty-five sheets: five east–west and five north–south. Each sheet of the map showed two scales, one purely [[Metric system|metric]], the other in Swiss [[League (unit)|leagues]] 4800 metres in length. The frame was divided into [[Degree (angle)|sexagesimal]] [[Minute and second of arc|minutes]] and centesimal minutes; the latter, each subdivided into ten parts, had the advantage of showing [[Kilometre]]s in the direction of the [[Meridian (geography)|meridians]]; so that there were new scales on the sides of the sheet to evaluate the distances.<ref name=":6">{{Cite web|title=Cartographie|url=https://hls-dhs-dss.ch/articles/008258/2014-11-26/|access-date=12 March 2021|website=hls-dhs-dss.ch|language=fr|archive-date=2 February 2021|archive-url=https://web.archive.org/web/20210202081004/https://hls-dhs-dss.ch/articles/008258/2014-11-26/|url-status=live}}</ref><ref name=":7">{{cite journal |last1=Dufour |first1=G.-H. |title=Notice sur la carte de la Suisse dressée par l'État Major Fédéral |journal=Le Globe. Revue genevoise de géographie |date=1861 |volume=2 |issue=1 |pages=5–22 |doi=10.3406/globe.1861.7582}}</ref><ref>{{Cite web|title=Systèmes de référence historiques|url=https://www.swisstopo.admin.ch/fr/connaissances-faits/histoire-collections/cartes-historiques/references-historiques.html|access-date=12 March 2021|website=Office fédéral de topographie swisstopo|language=fr|archive-date=26 November 2020|archive-url=https://web.archive.org/web/20201126212909/https://www.swisstopo.admin.ch/fr/connaissances-faits/histoire-collections/cartes-historiques/references-historiques.html|url-status=dead}}</ref>

According to the [[Swiss Federal Constitution|1848 Constitution]] the federal foot was to come into force throughout the country. In [[Geneva]], a committee chaired by [[Guillaume Henri Dufour]] militated in favor of maintaining the decimal metric system in the French-speaking cantons and against the standardization of weights and measures in Switzerland on the basis of the metric foot. In 1868 the metric system was legalized alongside the federal foot, which was a first step towards its definitive introduction. Cantonal calibrators were supervised by a [[Federal Institute of Metrology|Federal Bureau of Verification]] created in 1862, whose management was entrusted to [[Heinrich von Wild]] from 1864. In 1875, the responsibility for weights and measures was transferred back from the cantons to the Confederation, and [[Switzerland]] (represented by [[Adolphe Hirsch]]) joined the [[Metre Convention]]. The same year a federal law imposed the metric system from 1 January 1877. In 1977, Switzerland joined the [[International System of Units]].<ref name=":5" /><ref name=":4" /><ref>{{Cite web|title=Hirsch, Adolphe|url=https://hls-dhs-dss.ch/articles/032026/2005-05-10/|access-date=8 January 2021|website=hls-dhs-dss.ch|language=fr|archive-date=24 November 2020|archive-url=https://web.archive.org/web/20201124232607/https://hls-dhs-dss.ch/articles/032026/2005-05-10/|url-status=live}}</ref><ref>{{Cite web|title=Journal de Genève - 22.03.1854 - Page 1|url=https://www.letempsarchives.ch/page/JDG_1854_03_22/1/article/5203313|access-date=12 March 2021|website=www.letempsarchives.ch|archive-date=7 November 2023|archive-url=https://web.archive.org/web/20231107040659/https://www.letempsarchives.ch/page/JDG_1854_03_22/1/article/5203313|url-status=live}}</ref><ref>{{Cite web|title=Journal de Genève - 14.02.1852 - Page 4|url=https://www.letempsarchives.ch/page/JDG_1852_02_14/4|access-date=12 March 2021|website=www.letempsarchives.ch|archive-date=7 November 2023|archive-url=https://web.archive.org/web/20231107040705/https://www.letempsarchives.ch/page/JDG_1852_02_14/4|url-status=live}}</ref>

===United Kingdom (1824–present)===
{{Main|Metrication in the United Kingdom}}

The [[Weights and Measures Act 1824]] ([[5 Geo. 4]]. c. 74) imposed one standard 'imperial' system of weights and measures on the British Empire.<ref>{{cite web
|url = http://www.parliament.uk/about/living-heritage/transformingsociety/tradeindustry/industrycommunity/keydates/
|title = Industry and community – Key dates
|publisher = United Kingdom Parliament
|access-date = 28 March 2011
|archive-date = 6 November 2010
|archive-url = https://web.archive.org/web/20101106184932/http://www.parliament.uk/about/living-heritage/transformingsociety/tradeindustry/industrycommunity/keydates/
|url-status = live
}}</ref> The effect of this act was to standardise existing British units of measure rather than to align them with the metric system.

During the next eighty years a number of parliamentary select committees recommended the adoption of the metric system, each with a greater degree of urgency, but Parliament prevaricated. A select committee report of 1862 recommended compulsory metrication, but with an "Intermediate permissive phase"; Parliament responded in 1864 by legalising metric units only for 'contracts and dealings'.<ref name="Hyttel">{{Cite thesis
 |degree      = BA
 |title       = Working man's pint – An investigation of the implementation of the metric system in Britain 1851–1979
 |url         = http://ukma.org.uk/sites/default/files/hyttel_metrication.pdf
 |author      = Frederik Hyttel
 |date        = May 2009
 |publisher   = Bath Spa University
 |location    = [[Bath, Somerset|Bath]], United Kingdom
 |access-date  = 29 March 2011
|archive-url  = https://web.archive.org/web/20160306063341/http://ukma.org.uk/sites/default/files/hyttel_metrication.pdf
 |archive-date = 6 March 2016
|url-status     = dead
 |df          = dmy-all
}}</ref> The United Kingdom initially declined to sign the [[Treaty of the Metre]], but did so in 1883. Meanwhile, British scientists and technologists were at the forefront of the metrication movement – it was the [[British Association for the Advancement of Science]] that promoted the [[CGS system of units]] as a coherent system<ref name="SIBrochure">{{SIBrochure8th}}</ref>{{rp| 109}} and it was the British firm [[Johnson Matthey]] that was accepted by the CGPM in 1889 to cast the international prototype metre and kilogram.<ref name="CGPMprototypes">{{cite journal |last1=Jabbour |first1=Z.J. |last2=Yaniv |first2=S.L. |title=The kilogram and measurements of mass and force |journal=Journal of Research of the National Institute of Standards and Technology |date=January 2001 |volume=106 |issue=1 |pages=25–46 |doi=10.6028/jres.106.003 |pmid=27500016 |pmc=4865288}}</ref>

In 1895, another parliamentary select committee recommended the compulsory adoption of the metric system after a two-year permissive period. The [[Weights and Measures (Metric System) Act 1897]] ([[60 & 61 Vict.]] c. 46) legalised the metric units for trade, but did not make them mandatory.<ref name = Hyttel/> A bill to make the metric system compulsory to help the British industrial base fight off the challenge of the nascent German base passed through the House of Lords in 1904, but did not pass in the House of Commons before the next general election was called. Following opposition by the Lancashire cotton industry, a similar bill was defeated in the House of Commons in 1907 by 150 votes to 118.<ref name = Hyttel/>

In 1965, the UK began an official programme of metrication, and as of {{currentyear}}, in the [[United Kingdom]] the metric is the official measurement system for all regulated trading by weight or measure purposes, however the imperial [[pint]] remains the sole legal unit for milk in returnable bottles and for draught beer and cider in British pubs. Imperial units are also legally permitted to be used alongside metric units on food packaging and price indications for goods sold loose.<ref>{{Cite web |title=Weights and measures: the law |url=https://www.gov.uk/weights-measures-and-packaging-the-law |access-date=2024-02-12 |website=GOV.UK |language=en |archive-date=30 October 2023 |archive-url=https://web.archive.org/web/20231030170848/https://www.gov.uk/weights-measures-and-packaging-the-law |url-status=live }}</ref> The UK government undertook a "Choice on units of measurement: consultation response", and found just over 1% of respondents wish to revert to an increase the use of imperial units,  and as such kept the current regulations on the sale of goods.<ref>{{Cite web |title=Choice on units of measurement: consultation response |url=https://www.gov.uk/government/consultations/choice-on-units-of-measurement-markings-and-sales/outcome/choice-on-units-of-measurement-consultation-response |access-date=2024-02-12 |website=GOV.UK |language=en |archive-date=20 January 2024 |archive-url=https://web.archive.org/web/20240120162306/https://www.gov.uk/government/consultations/choice-on-units-of-measurement-markings-and-sales/outcome/choice-on-units-of-measurement-consultation-response |url-status=live }}</ref>

In addition imperial units may be used exclusively where a product is sold by description, rather than by weight/mass/volume: e.g. television screen and clothing sizes tend to be given in inches only, but a piece of material priced per inch would be unlawful unless the metric price was also shown.

The general public still use imperial units in common langange for their height and weight, and imperial units are the norm when discussing longer distances such as journeys by car, but otherwise metric measurements are often used.{{citation needed|date=August 2022}}

===United States (1830–present)===
{{Main|Metrication in the United States}}
[[File:Ferdinand Randolph Hassler LCCN2003655032.jpg|thumb|upright=0.75|Ferdinand Rudolph Hassler, first superintendent of the [[United States Coast and Geodetic Survey|United States Coast Survey]]|left]]
In 1805 a Swiss geodesist [[Ferdinand Rudolph Hassler]] brought copies of the French metre and kilogram to the United States.<ref>{{Cite web |url=http://www.f-r-hassler.ch/en/emigration/index.html |title=Emigration: Off to New Shores |website=E-Expo Ferdinand Rudolf Hassler |publisher=METAS |access-date=19 December 2017 |archive-date=12 February 2018 |archive-url=https://web.archive.org/web/20180212000054/http://www.f-r-hassler.ch/en/emigration/index.html |url-status=live }}</ref><ref name=":1">{{Cite journal|last=Cajori|first=Florian|date=1921|title=Swiss Geodesy and the United States Coast Survey|url=https://www.jstor.org/stable/6721|journal=The Scientific Monthly|volume=13|issue=2|pages=117–129|bibcode=1921SciMo..13..117C|issn=0096-3771|access-date=4 January 2021|archive-date=6 June 2021|archive-url=https://web.archive.org/web/20210606111103/https://www.jstor.org/stable/6721|url-status=live}}</ref> In 1830 the Congress decided to create uniform standards for length and weight in the United States.<ref name=":0">{{Cite web |url=http://www.f-r-hassler.ch/en/weights/index.html |title=Weights and Measures: New Standards for the USA |website=E-Expo Ferdinand Rudolf Hassler |publisher=METAS |access-date=19 December 2017 |archive-date=12 February 2018 |archive-url=https://web.archive.org/web/20180212000139/http://www.f-r-hassler.ch/en/weights/index.html |url-status=live }}</ref> [[Ferdinand Rudolph Hassler|Hassler]] was mandated to work out the new standards and proposed to adopt the [[metric system]].<ref name=":0" /> The Congress opted for the British Parliamentary Standard from 1758 and the Troy Pound of Great Britain from 1824 as length and weight standards.<ref name=":0" /> Nevertheless, the primary baseline of the Survey of the Coast (renamed the United States Coast Survey in 1836 and the [[United States Coast and Geodetic Survey]] in 1878) was measured in 1834 at [[Fire Island]] using four {{convert|2|m|adj=on}} iron bars constructed after Hassler's specification in the United Kingdom and brought back in the United States in 1815.<ref>{{Cite web |url=https://www.nist.gov/sites/default/files/documents/nvl/HasslerSP1068.pdf |title=NIST Special Publication 1068 Ferdinand Rudolph Hassler (1770–1843) A Twenty Year Retrospective, 1987–2007 |website=NIST |pages=51–52 |access-date=27 November 2017 |archive-date=31 January 2017 |archive-url=https://web.archive.org/web/20170131034513/https://www.nist.gov/sites/default/files/documents/nvl/HasslerSP1068.pdf |url-status=dead}}</ref><ref>{{Cite web |url=http://www.f-r-hassler.ch/en/interlude/index.html |title=Interlude in Europe: Ups... and Downs... |website=E-Expo Ferdinand Rudolf Hassler |publisher=METAS |access-date=19 December 2017 |archive-date=12 February 2018 |archive-url=https://web.archive.org/web/20180212000220/http://www.f-r-hassler.ch/en/interlude/index.html |url-status=live }}</ref><ref name=":1" /> All distances measured by the Survey of the Coast, Coast Survey, and Coast and Geodetic Survey were referred to the metre.<ref name=":2">{{cite journal |title=XIII. Results of the comparisons of the standards of length of England, Austria, Spain, United States, Cape of Good Hope, and of a second Russian standard, made at the Ordnance Survey Office, Southampton. With a preface and notes on the Greek and Egyptian measures of length by Sir Henry James |journal=Philosophical Transactions of the Royal Society of London |date=31 December 1873 |volume=163 |pages=445–469 |doi=10.1098/rstl.1873.0014 |doi-access=free}}</ref><ref name=":3">{{Cite book|last=Hassler|first=Ferdinand Rudolf|date=1825|title=Transactions of the American Philosophical Society|url=https://www.biodiversitylibrary.org/page/4482470|access-date=|volume=2|page=252|archive-date=8 April 2023|archive-url=https://web.archive.org/web/20230408175517/https://www.biodiversitylibrary.org/page/4482470|url-status=live}}</ref> In 1866 the [[United States Congress]] passed a bill making it lawful to use the metric system in the United States. The bill, which was permissive rather than mandatory in nature, defined the metric system in terms of [[United States customary units|customary units]] rather than with reference to the international prototype metre and kilogram.<ref>{{cite web
 |url=http://lamar.colostate.edu/~hillger/laws/metric-act-bill.html 
 |title=H.R. 596, An Act to authorize the use of the metric system of weights and measures 
 |author=29th Congress of the United States, Session 1 
 |date=13 May 1866 |access-date=19 May 2011 |url-status=dead 
 |archive-url=https://web.archive.org/web/20150705015307/https://lamar.colostate.edu/~hillger/laws/metric-act-bill.html 
 |archive-date=5 July 2015}}</ref><ref name=Barbrowetal/>{{rp|10–13}} Ferdinand Rudolph Hassler's use of the metre in coastal surveying, which had been an argument for the introduction of the [[Metric Act of 1866]] allowing the use of the metre in the United States, probably also played a role in the choice of the metre as international scientific unit of length and the proposal by the [[International Association of Geodesy|European Arc Measurement]] (German: ''Europäische Gradmessung'') to “establish a European [[International Bureau of Weights and Measures|international bureau for weights and measures]]”.<ref name=":3" /><ref name=":2" /><ref>{{Cite web|title=Metric Act of 1866 – US Metric Association|url=https://usma.org/laws-and-bills/metric-act-of-1866#locale-notification|access-date=4 January 2021|website=usma.org|archive-date=28 February 2021|archive-url=https://web.archive.org/web/20210228052918/https://usma.org/laws-and-bills/metric-act-of-1866#locale-notification|url-status=live}}</ref><ref>{{Cite book|last=|first=|url=http://gfzpublic.gfz-potsdam.de/pubman/item/escidoc:108187:4/component/escidoc:272449/Generalbericht.mitteleurop%C3%A4ische.Gradmessung%201867.pdf|title=Bericht über die Verhandlungen der vom 30. September bis 7. October 1867 zu BERLIN abgehaltenen allgemeinen Conferenz der Europäischen Gradmessung|publisher=Central-Bureau der Europäischen Gradmessung|year=1868|isbn=|location=Berlin|pages=123–134|language=de}}</ref>

By 1893, the reference standards for customary units had become unreliable. Moreover, the United States, being a signatory of the [[Metre Convention]] was in possession of national prototype metres and kilograms that were calibrated against those in use elsewhere in the world. This led to the [[Mendenhall Order]] which redefined the customary units by referring to the national metric prototypes, but used the conversion factors of the 1866 act.<ref name="Barbrowetal">{{cite book
 |url         = https://www.nist.gov/pml/pubs/sp447/index.cfm
 |title       = Weights and Measures Standards of the United States: A brief history
 |first1      = Louis E.
 |last1       = Barbrow
 |first2      = Lewis V.
 |last2       = Judson
 |publisher   = NIST
 |year        = 1976
 |access-date  = 19 May 2011
|url-status     = dead
 |archive-url  = https://web.archive.org/web/20110603064530/https://www.nist.gov/pml/pubs/sp447/index.cfm
 |archive-date = 3 June 2011
}}</ref>{{rp|16–20}} In 1896, a bill that would make the metric system mandatory in the United States was presented to Congress. Twenty-three of the 29 people who gave evidence before the congressional committee who were considering the bill were in favor of it, but six were against. Four of these six dissenters represented manufacturing interests and the other two were from the United States Revenue service. The grounds cited were the cost and inconvenience of the change-over. The bill was not enacted. Subsequent bills suffered a similar fate.<ref name="PopularScience" />

The United States mandated the acceptance of the metric system in 1866 for commercial and legal proceedings, without displacing their customary units.<ref name="United States Metric Laws and Treaties">{{cite web |url=http://ts.nist.gov/WeightsAndMeasures/Metric/upload/HR-596-Metric-Law-1866.pdf |title=Metric Act of 1866 |publisher=Metric Program, Weights and Measures Division, United States National Institute of Standards, Technology and Technology |access-date=10 November 2009 |url-status=dead |archive-url=https://web.archive.org/web/20100527161529/http://ts.nist.gov/WeightsAndMeasures/Metric/upload/HR-596-Metric-Law-1866.pdf |archive-date=27 May 2010}}<br /> {{cite web | title = U.S. Metric System (SI) Legal Resources | url = http://ts.nist.gov/WeightsAndMeasures/Metric/Federal_Metric_Policy.cfm#legal | publisher = Metric Program, Weights and Measures Division, United States National Institute of Standards, Technology and Technology | access-date = 11 November 2009 | url-status = dead | archive-url = https://web.archive.org/web/20090801172441/http://ts.nist.gov/WeightsAndMeasures/Metric/Federal_Metric_Policy.cfm#legal | archive-date = 1 August 2009 | df = dmy-all}}</ref> The non-mandatory nature of the adoption of the SI has resulted in a much slower pace of adoption in the US than in other countries.<ref>{{cite journal |last1=Smith |first1=Jeanette C. |title=Take Me to Your Liter |journal=Journal of Government Information |date=September 1998 |volume=25 |issue=5 |pages=419–438 |doi=10.1016/S1352-0237(98)00030-6}}</ref>

In 1971, the US [[National Institute of Standards and Technology|National Bureau of Standards]] completed a three-year study of the impact of increasing worldwide metric use on the US. The study concluded with a report to Congress entitled ''[[A Metric America&nbsp;– A Decision Whose Time Has Come]]''. Since then metric use has increased in the US, principally in the manufacturing and educational sectors. Public Law 93-380, enacted 21 August 1974, states that it is the policy of the US to encourage educational agencies and institutions to prepare students to use the metric system of measurement with ease and facility as a part of the regular education program. On 23 December 1975, President Gerald Ford signed Public Law 94–168, the [[Metric Conversion Act]] of 1975. This act declares a national policy of coordinating the increasing use of the metric system in the US. It established a US Metric Board whose functions as of 1 October 1982 were transferred to the Dept of Commerce, Office of Metric Programs, to coordinate the voluntary conversion to the metric system.<ref>{{Cite book
 |editor = Howard B. Bradley
 |title = Petroleum Engineering Handbook
 |pages = 1–69
 |year = 1987
 |publisher = Society of Petroleum Engineers
 |isbn = 978-1555630102
}}</ref>

In January 2007 [[NASA]] decided to use metric units for all future Moon missions, in line with the practice of other space agencies.<ref name="MetricMoon">{{cite web
 |url=https://science.nasa.gov/science-news/science-at-nasa/2007/08jan_metricmoon/
 |title=Metric Moon
 |year=2007
 |publisher=[[NASA]]
 |access-date=6 April 2010
|archive-date=11 July 2010
|archive-url=https://web.archive.org/web/20100711000119/http://science.nasa.gov/science-news/science-at-nasa/2007/08jan_metricmoon/
 |url-status=dead
}}</ref>

===Other English-speaking countries===

The British metrication programme signalled the start of metrication programmes elsewhere in the [[Commonwealth of Nations|Commonwealth]], though India had started its programme in 1959, six years before the United Kingdom. South Africa (then not a member of the Commonwealth) set up a Metrication Advisory Board in 1967, New Zealand set up its Metric Advisory Board in 1969, Australia passed the Metric Conversion Act in 1970 and Canada appointed a Metrication Commission in 1971. 
[[File:Canadian canned food labels showing imperial and metric units of measurement.jpg|thumb|upright=1.35|left|The metric units of measurement on Canadian canned food labels are merely the equivalent of the still widely used imperial units such as the ounce.]]
Metrication in Australia, New Zealand and South Africa was essentially complete within a decade, while in Canada metrication has been halted since the 1970s. In Canada, the [[square foot]] is still widespread for commercial and residential advertisements and partially in construction because of the close trade relations with the United States. Metric measurements on food products such as canned food are often merely the equivalent of the still widely used imperial units of measurement such as the ounce and the pound. Butter in Canada is sold in 454 g packagings, which is the equivalent of one pound. The [[Rail transport in Canada|railways of Canada]] such as the [[Canadian National Railway|Canadian National]] and [[Canadian Pacific Railway|Canadian Pacific]] as well as [[commuter rail]] services continue to measure their trackage in miles and speed limits in miles per hour because they also operate in the United States (although urban railways including [[Rapid transit|subways]] and [[light rail]] have adopted kilometres and kilometres per hour).<ref>{{cite web |url=http://www.tc.gc.ca/eng/railsafety/rules-tce31-98.htm |title=A. Classes of Track - Transport Canada |website=www.tc.gc.ca |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20120825070252/http://www.tc.gc.ca/eng/railsafety/rules-tce31-98.htm |archive-date=25 August 2012 |url-status=dead}}</ref> Canadian railcars show weight figures in both imperial and metric. Most other Commonwealth countries adopted the metric system during the 1970s.<ref>{{cite web
 |url=http://lamar.colostate.edu/~hillger/internat.htm 
 |title=Metrication status and history 
 |publisher=United States Metrication Association 
 |year=2009 
 |access-date=19 May 2011 |url-status=dead 
 |archive-url=https://web.archive.org/web/20100724200113/http://lamar.colostate.edu/~hillger/internat.htm 
 |archive-date=24 July 2010}}</ref>

Apart from the United Kingdom and Canada, which have effectively halted their metrication programs, the great majority of countries using the imperial system have completed official metrication during the second half of the 20th century or the first decade of the 21st century. The most recent to complete this process was the [[Republic of Ireland]], which began metric conversion in the 1970s and completed it in early 2005.<ref>{{cite web|url=https://www.independent.co.uk/life-style/motoring/features/ireland-goes-metric--fast-531570.html|archive-url=https://web.archive.org/web/20141029022100/http://www.independent.co.uk/life-style/motoring/features/ireland-goes-metric--fast-531570.html|url-status=dead|archive-date=29 October 2014|title=Ireland goes metric - fast|work=The Independent|access-date=24 November 2014}}</ref> [[Hong Kong units of measurement|Hong Kong uses three systems]] (Chinese, imperial, and metric) and all three are permitted for use in trade.<ref name="Ordinance">{{Cite web |url=http://www.hklii.hk/eng/hk/legis/ord/68/sch2.html |title=Cap 68 Sched 2 Units of Measurement and Permitted Symbols or Abbreviations of Units of Measurement Lawful for Use for Trade |access-date=28 April 2020 |archive-date=3 September 2015 |archive-url=https://web.archive.org/web/20150903233217/http://www.hklii.hk/eng/hk/legis/ord/68/sch2.html |url-status=dead}}</ref>