Imperiales Einheitensystem

2021-09-24T05:31:42Z

121.200.5.79: /* Current use */ added Bahamas

{{short description|System of units that were implemented on 1 January 1826 in the British Empire}}
{{About|the post-1824 measures used in the British Empire and countries in the British sphere of influence|the units used in England before 1824|English units|the system of weight|Avoirdupois system|United States customary units|United States customary units|an overview of UK and US units|Imperial and US customary measurement systems|the political ideology|Imperialism}}
{{Use dmy dates|date=November 2020}}
[[File:Weights and Measures office.jpg|thumb|upright=1.2|The former Weights and Measures office in [[Seven Sisters, London]] (590 Seven Sisters Road)]]

The '''imperial system of units''', '''imperial system''' or '''imperial units''' (also known as '''British Imperial'''<ref name="Publishing2010">{{cite book|author=Britannica Educational Publishing|title=The Britannica Guide to Numbers and Measurement|url=https://books.google.com/books?id=cuN7rH6RzikC&pg=PA241|year=2010|publisher=The Rosen Publishing Group|isbn=978-1-61530-218-5|page=241}}</ref> or '''Exchequer Standards''' of 1826) is the [[system of units]] first defined in the British [[Weights and Measures Act 1824]] and continued to be developed through a series of Weights and Measures Acts and amendments.

The imperial system developed from earlier [[English units]] as did the [[Comparison of the imperial and US customary measurement systems|related but differing system]] of [[United States customary units|customary units of the United States]]. The imperial units replaced the [[Winchester measure|Winchester Standards]], which were in effect from 1588 to 1825.<ref>{{cite book|author=Chaney, Henry James|title=A Practical Treatise on the Standard Weights and Measures in Use in the British Empire with some account of the metric system|url=https://archive.org/details/ourweightsandme00changoog|access-date=11 September 2016|date=1897|publisher=Eyre and Spottiswoode|page=[https://archive.org/details/ourweightsandme00changoog/page/n11 3]}}</ref> The system came into official use across the [[British Empire]] in 1826.

By the late 20th century, most nations of the former empire had [[metrication|officially adopted]] the [[metric system]] as their main system of measurement, but imperial units are still used alongside metric units in the United Kingdom and in some other parts of the former empire, notably Canada.

The modern legislation defining the imperial system of units is given in the [[Weights and Measures Act 1985]] (as amended).<ref>{{Cite web|url=http://www.legislation.gov.uk/ukpga/1985/72|title=Weights and Measures Act 1985 |website=legislation.gov.uk |access-date=2020-01-20}}</ref>

==Implementation==
The Weights and Measures Act of 1824 was initially scheduled to go into effect on 1 May 1825.<ref name="google339">{{cite book|author=Great Britain|title=The statutes of the United Kingdom of Great Britain and Ireland (1807-1865)|url=https://archive.org/details/statutesunitedk02britgoog|access-date=31 December 2011|year=1824|publisher=His Majesty's statute and law printers|pages=[https://archive.org/details/statutesunitedk02britgoog/page/n373 339]–354}}</ref> The Weights and Measures Act of 1825 pushed back the date to 1 January 1826.<ref>{{cite book|author1=Great Britain|author2=William David Evans|author-link2=William David Evans|author3=Anthony Hammond|author4=Thomas Colpitts Granger|title=A collection of statutes connected with the general administration of the law: arranged according to the order of subjects|url=https://archive.org/details/acollectionstat08evangoog|access-date=31 December 2011|year=1836|publisher=W. H. Bond|pages=[https://archive.org/details/acollectionstat08evangoog/page/n397 306]–27}}</ref> The 1824 Act allowed the continued use of pre-imperial units provided that they were customary, widely known, and clearly marked with imperial equivalents.<ref name="google339"/>

===Apothecaries' units===
[[File:Imperial standards of length 1876 Trafalgar Square.jpg|thumb|right|Imperial standards of length 1876 in [[Trafalgar Square]], London.]]

[[Apothecaries' system|Apothecaries' units]] are mentioned neither in the act of 1824 nor 1825. At the time, apothecaries' weights and measures were regulated "in England, Wales, and [[Berwick-upon-Tweed]]" by the [[London College of Physicians]], and in Ireland by the [[Royal College of Physicians of Ireland|Dublin College of Physicians]]. In Scotland, apothecaries' units were unofficially regulated by the [[Edinburgh College of Physicians]]. The three colleges published, at infrequent intervals, [[pharmacopoeia]]s, the London and Dublin editions having the force of law.<ref name="Edinburgh medical and surgical journal">{{cite book|title=Edinburgh medical and surgical journal|url=https://books.google.com/books?id=DwUbAQAAMAAJ&pg=PA398|year=1824|publisher=A. and C. Black|page=398}}</ref><ref name="IrelandButler1765">{{cite book|author1=Ireland|last2=Butler|first2=James Goddard|last3=Ball|first3=William (barrister.)|title=The Statutes at Large, Passed in the Parliaments Held in Ireland: From the twenty-third year of George the Second, A.D. 1749, to the first year of George the Third, A.D. 1761 inclusive|url=https://books.google.com/books?id=iIdRAAAAYAAJ&pg=PA852|year=1765|publisher=Boulter Grierson|page=852}}</ref>

Imperial apothecaries' measures, based on the imperial pint of 20 fluid ounces, were introduced by the publication of the London Pharmacopoeia of 1836,<ref name="Gray1836">{{cite book|last=Gray|first=Samuel Frederick|author-link=Samuel Frederick Gray|title=A supplement to the Pharmacopœia and treatise on pharmacology in general: including not only the drugs and preparations used by practitioners of medicine, but also most of those employed in the chemical arts : together with a collection of the most useful medical formulæ ...|url=https://archive.org/details/supplementtophar00grayuoft|access-date=29 July 2012|year=1836|publisher=Longman, Rees, Orme, Brown, Green, and Longman|page=[https://archive.org/details/supplementtophar00grayuoft/page/516 516]}}</ref><ref>{{cite web|url=https://archive.org/stream/atranslationpha01philgoog#page/n19/mode/2up|title=A Translation of the Pharmacopoeia of the Royal College of Physicians of London, 1836.: With ...|publisher=S. Highley, 32, Fleet Street.|year=1837}}</ref> the Edinburgh Pharmacopoeia of 1839,<ref name="The Pharmacopoeia of the Royal College of Physicians of Edinburgh">{{cite book|title=The Pharmacopoeia of the Royal College of Physicians of Edinburgh|url=https://books.google.com/books?id=sTjY2_xKm9UC&pg=PR13|year=1839|publisher=Adam and Charles Black and Bell and Bradfute|pages=xiii–xiv}}</ref> and the Dublin Pharmacopoeia of 1850.<ref name="DublinIreland1850">{{cite book|author1=Royal College of Physicians of Dublin|author2=Royal College of Physicians of Ireland|author-link2=Royal College of Physicians of Ireland|title=The pharmacopœia of the King and queen's college of physicians in Ireland|url=https://archive.org/details/pharmacopiaking00dublgoog|access-date=29 July 2012|year=1850|publisher=Hodges and Smith|page=xxii}}</ref> The Medical Act of 1858 transferred to [[The Crown]] the right to publish the official pharmacopoeia and to regulate apothecaries' weights and measures.<ref name="Britain1858">{{cite book|author=Great Britain|title=A collection of the public general statutes passed in the ... year of the reign of ...|url=https://books.google.com/books?id=rkovAAAAIAAJ&pg=PA306|year=1858|publisher=Printed by G. W. Eyre and W. Spottiswoode, Printers to the Queen|page=306}}</ref>

==Units==

===Length===
Metric equivalents in this article usually assume the latest official definition. Before this date, the most precise measurement of the imperial Standard Yard was {{val|0.914398415}} metres.<ref>Sears et al. 1928. ''Phil Trans A'', 227:281.</ref>
{{Clear}}
{| class="wikitable" style="margin-right:0"
|+ Table of length equivalent units
! Unit
!Abbr. or symbols
! Relative to previous
! Feet
! [[Metres]]
! Notes
|-
![[twip]]
|
|
|align=right| {{frac|{{val|17280}}}}
|align=right| {{val|0.0000176389}}
|
|
|-
![[thou (length)|thou]]
|th
|
|align=right| {{frac|{{val|12000}}}}
|align=right| {{val|0.0000254}}
|
Also known as ''mil''<ref name="jerrard">Jerrard and McNeill, Dictionary of Scientific Units, second edition, Chapman and Hall; cites first appearance in print in Journal of the Institution of Electrical Engineers (G.B.) vol. 1, page 246 (1872)</ref>
|-
![[Barleycorn (unit)|barleycorn]]
| Bc<ref>{{Cite web|title=BARLEYCORN {{!}} Definition of BARLEYCORN by Oxford Dictionary on Lexico.com also meaning of BARLEYCORN|url=https://www.lexico.com/definition/barleycorn|access-date=2021-04-19|website=Lexico Dictionaries {{!}} English|language=en}}</ref>
| {{nowrap|{{Fraction|333|1|3}} th}}
|align="right" | {{frac|36}}
|{{val|0.0084667}}
| {{nowrap|{{Fraction|1|3}} in}}
|-
![[inch]]
|{{cslist|in|[[Prime (symbol)|″]]}}
| {{val|3|u=Bc}}
| align="right" | {{frac|12}}
| align="right" | {{val|0.0254}}
| 1 metre ≈ {{val|39.3701|u=inch}}
|-
![[Hand (unit)|hand]]
|h
| {{val|4|u=inch}}
|align="right" | {{frac|3}}
|align="right" | {{val|0.1016}}
| Still used in English-speaking (i.e., US and Commonwealth) nations to measure heights of horses.
|
|-
![[Foot (unit)|foot]]
|{{cslist|ft|[[Prime (symbol)|′]]}}
| {{val|12|u=inch}}
|align=right| 1
|align=right| {{val|0.3048}}
|
|-
![[yard]]
|yd
| {{val|3|u=foot}}
|align=right| 3
|align=right| {{val|0.9144}}
| Defined as exactly {{val|0.9144|u=metres}} by the [[international yard and pound]] agreement of 1959
|-
![[Chain (unit)|chain]]
|ch
| {{val|22|u=yard}}
|align=right| 66
|align=right| {{val|20.1168}}
| {{val|100|u=links}}, {{val|4|u=rods}}, or {{frac|10}} of a furlong. The distance between the two [[wicket]]s on a [[cricket pitch]].
|-
![[furlong]]
|fur
| {{val|10|u=chain}}
|align=right| {{val|660}}
|align=right| {{val|201.168}}
| {{val|220|u=yards}}
|-
![[mile]]
|mi
| {{val|8|u=furlong}}
|align=right| {{val|5280}}
|align=right| {{val|1609.344}}
| {{val|1760|u=yards}} or {{val|80|u=chain}}
|-
![[league (unit)|league]]
|lea
| {{val|3|u=mile}}
|align=right| {{val|15840}}
|align=right| {{val|4828.032}}
| No longer an official unit in any nation.{{citation needed|date=June 2017}}
|-
| colspan="6" style="text-align:center;" | '''Maritime units'''
|- valign=top
![[fathom]]
|ftm
| {{val|2.02667|u=yard}}
|align=right| {{val|6.0761}}
|align=right| {{val|1.852}}
| The British Admiralty in practice used a fathom of {{val|6|u=foot}}. This was despite its being {{frac|1000}} of a nautical mile (i.e. {{val|6.08|u=foot}}) until the adoption of the international nautical mile.<ref name="fath">The exact figure was {{val|6.08|u=foot}}, but {{val|6|u=foot}} was in use in practice. The commonly accepted definition of a fathom was always 6 feet. The conflict was inconsequential, as Admiralty nautical charts designated depths shallower than {{val|5|u=fathom}} in feet on older imperial charts. Today, all charts worldwide are metric, except for USA Hydrographic Office charts, which use feet for all depth ranges.</ref>
|- valign=top
![[cable length|cable]]
|
| {{val|100|u=fathom}}
|align=right| {{val|607.61}}
|align=right| {{val|185.2}}
| One tenth of a nautical mile. Equal to {{val|100|u=fathom}} under the strict definition.
|- valign=top
![[nautical mile]]
|nmi
| {{val|10|u=cables}}
|align=right| {{val|6076.1}}
|align=right| {{val|1852}}
| Used for measuring distances at sea (and also in aviation) and approximately equal to one [[arc minute]] of a [[great circle]]. Until the adoption of the international definition of {{val|1852|u=metre}} in 1970, the British nautical (Admiralty) mile was defined as {{val|6080|u=foot}}.<ref>The [[nautical mile]] was not readily expressible in terms of any of the intermediate units, because it was derived from the circumference of the Earth (like the original metre).</ref>
|-
| colspan="6" style="text-align:center;" | '''Gunter's survey units (17th century onwards)'''
|-
![[link (unit)|link]]
|
| {{val|7.92|u=inch}}
|align=right| {{frac|66|100}}
|align=right| {{val|0.201168}}
| {{frac|100}} of a chain and {{frac|{{val|1000}}}} of a furlong
|-
![[Rod (unit)|rod]]
|
| {{val|25|u=links}}
|align=right| {{frac|66|4}}
|align=right| {{val|5.0292}}
| The rod is also called ''pole'' or ''perch'' and equal to {{nowrap|{{frac|5|1|2}} yards}}
|}

===Area===
{| class="wikitable" style="margin-right:0"
|+ Table of area units and equivalents
! Unit
!Abbr. or symbol
!Relative to previous
! Relation to units of length
! Square feet
! Square yards
! Acres
! Square metres
! [[Hectare]]s
! Notes
|-
! [[Perch (area)|perch]]
|
|
|{{val|1|u=rod}} × {{val|1|u=rod}}
|align=right| {{frac|272|1|4}}
|align=right| {{Fraction|30|1|4}}
|align=right| {{frac|160}}
|align=right| {{val|25.29285264}}
|align=right| {{val|0.002529285264}}
|The ''square rod'' has been called a ''pole'' or ''perch'' or, more properly, ''square pole'' or ''square perch'' for centuries.
|-
! [[Rood (unit)|rood]]
|
| {{val|40|u=perch}}
| {{val|1|u=furlong}} × {{val|1|u=rod}}<ref>{{cite web|url=http://ts.nist.gov/WeightsAndMeasures/Publications/upload/h4402_appenc.pdf |title=Appendix C: General Tables of Units of Measurements |access-date=4 January 2007 |publisher=NIST |url-status=dead|archive-url=https://web.archive.org/web/20061126120208/http://ts.nist.gov/WeightsAndMeasures/Publications/upload/h4402_appenc.pdf |archive-date=26 November 2006 }}</ref>
|align=right| {{val|10890}}
|align=right|{{Val|1210}}
|align=right| {{frac|4}}
|align=right| {{val|1011.7141056}}
|align=right| {{val|0.10117141056}}
|
|-
! [[acre]]
|
| {{val|4|u=rood}}
| {{val|1|u=furlong}} × {{val|1|u=chain}}
| align=right| {{val|43560}}
|align=right|{{Val|4840}}
|align=right| {{val|1}}
|align=right| {{val|4046.8564224}}
|align=right| {{val|0.40468564224}}
|
|-
![[square mile]]
|sq mi
|{{val|640|u=acre}}
|{{val|1|u=mile}} × {{val|1|u=mile}}
|align=right|{{Val|27878400}}
|align=right|{{Val|3097600}}
|align=right|640
|{{Val|2589988.110336}}
|{{Val|258.9988110336}}
|
|}

=== Volume ===
The [[Weights and Measures Act 1824]] invalidated the various different gallons in use in the British Empire, declaring them to be replaced by the [[statute measure|statute]] gallon (which became known as the imperial gallon), a unit close in volume to the [[gallon#History|ale gallon]]. The 1824 Act defined as the volume of a gallon to be that of {{convert|10|lb|kg|2}} of distilled water weighed in air with brass weights with the barometer standing at {{convert|30|inHg|0|lk=in}} at a temperature of {{convert|62|°F|°C|0|lk=in}}.<ref name="1824Act">{{cite web|url=http://www.legislation.gov.uk/ukpga/1824/74/pdfs/ukpga_18240074_en.pdf | title = An Act for ascertaining and establishing Uniformity of Weights and Measures (17 June 1824) | website= legislation.gov.uk | date = 17 June 1824 | access-date= 19 January 2020 |page = 639,640 |quote=Two such Gallons shall be a Peck, and Eight such Gallons shall be a Bushel, and Eight such Bushels a Quarter of Corn or other dry Goods, not measured by Heaped Measure.}}. (The date of coming into effect was 1 May 1825).</ref> The 1824 Act went on to give this volume as {{convert|277.274|cuin|l|abbr=off|sigfig=6}}.<ref name=1824Act /> The [[Weights and Measures Act 1963]] refined this definition to be the volume of 10 pounds of distilled water of density {{val|0.998859|u=g/mL}} weighed in air of density {{val|0.001217|u=g/mL}} against weights of density {{val|8.136|u=g/mL}}, which works out to {{val|4.546092|u=L}}.<ref group="nb">10 pounds = 4535.9237 grams. @ 0.998859 g/ml => 4546.092 ml</ref> The [[Weights and Measures Act 1985]] defined a gallon to be exactly {{val|4.54609|u=L}} (approximately {{val|277.4194|u=cuin}}).<ref>{{cite encyclopedia|url=http://www.sizes.com/units/gallon_imperial.htm|title=imperial gallon|website=Sizes.com|access-date=2019-07-10|date=25 October 2013}}</ref>

{| class="wikitable"
|+ Table of equivalences
! Unit
! Imperial ounces
! Imperial pints
! Millilitres
! Cubic inches
! US ounces
! US pints
|-
|align=center| ''[[fluid ounce]]'' (fl oz)
|align=right| 1    
|align=right| {{frac|20}}    
| {{convert|28.4130625|ml|cuin USoz USpt|disp=table|sigfig=5|comma=gaps}}
|-
|align=center| ''[[Gill (volume)|gill]]'' (gi)
|align=right| 5    
|align=right| {{frac|4}}    
| {{convert|142.0653125|ml|cuin USoz USpt|disp=table|sigfig=5|comma=gaps}}
|-
|align=center| ''[[pint]]'' (pt)
|align=right| 20    
|align=right| 1    
| {{convert|568.26125|ml|cuin USoz USpt|disp=table|sigfig=5|comma=gaps}}
|-
|align=center| ''[[quart]]'' (qt)
|align=right| 40    
|align=right| 2    
| {{convert|1136.5225|ml|cuin USoz USpt|disp=table|sigfig=5|comma=gaps}}
|-
|align=center| ''[[gallon]]'' (gal)
|align=right| 160    
|align=right| 8    
| {{convert|4546.09|ml|cuin USoz USpt|disp=table|sigfig=5|comma=gaps}}
|-
|colspan=7|'''Note:''' The millilitre equivalences are exact, but cubic-inch and US measures are correct to 5 significant figures.
|}

{| class="wikitable" style="margin-right:0"
|+ Unit measures defined by the Weights and Measures Act 1824, all measures determined by reference to the statute gallon of 277.274 cubic inches.<ref name=1824Act />
! Liquid
! Dry
! Capacity
|-
| {{1/2}} gill || ||{{convert|4.32|cuin|ml|abbr=on}}
|-
| gill || {{1/4}} pint||{{convert|8.64|cuin|ml|abbr=on}}
|-
| {{1/2}} pint || {{1/2}} pint ||{{convert|17.38|cuin|ml|abbr=on}}
|-
| pint || pint ||{{convert|34.76|cuin|ml l|abbr=on}}
|-
| quart || quart ||{{convert|69.32|cuin|l|abbr=on}}
|-
| {{1/2}} gallon || {{1/4}} peck or {{1/2}} gallon ||{{convert|138.64|cuin|l|abbr=on}}
|-
| gallon|| {{1/2}} peck or gallon||{{convert|277.274|cuin|l|abbr=on}}
|-
| 2 gallons (peck)||peck||{{convert|554.548|cuin|l|abbr=on}}
|-
| 4 gallons ({{1/2}} bushel)|| {{1/2}} bushel||{{convert|1109.096|cuin|l|abbr=on}}
|-
| 8 gallons ||[[bushel]] ||{{convert|2218.192|cuin|l|abbr=on}}
|-
| 64 gallons || [[Quarter (unit)|quarter]] ||{{convert|17745.536|cuin|l|abbr=on}}
|-
|colspan=3|'''Note:''' The 1824 Act removed the distinction between liquid and dry measure, specifying instead that the dry quantities shall be unheaped. The metric equivalences shown are approximate.
|}

====British apothecaries' volume measures====
These measurements were in use from 1826, when the new imperial gallon was defined. For pharmaceutical purposes, they were replaced by the metric system in the United Kingdom on 1 January 1971.<ref>{{cite web|url=http://www.legislation.gov.uk/uksi/1970/1897/introduction/made|title=The Weights and Measures (Equivalents for dealings with drugs) Regulations 1970}}</ref><ref>{{cite web |url=https://www.rpharms.com/Portals/0/MuseumLearningResources/11%20Balances%20Weights%20and%20Measures.pdf |title=Information Sheet: 11: Balances, Weights and Measures |website=Royal Pharmaceutical Society |access-date=11 December 2020}}</ref> In the US, though no longer recommended, the [[apothecaries' system]] is still used occasionally in medicine, especially in [[Medical prescription|prescriptions]] for older medications.<ref name="Zentz2010">{{cite book |last=Zentz |first=Lorraine C. |title=Math for Pharmacy Technicians |url=https://books.google.com/books?id=PvriGp6ZEhMC|year=2010|publisher=[[Jones & Bartlett Learning]] |location=Sudbury, MA |isbn=978-0-7637-5961-2 |oclc=421360709 |pages=7–8 |chapter=Chapter 1: Fundamentals of Math – Apothecary System |chapter-url=https://books.google.com/books?id=PvriGp6ZEhMC&pg=PA7 }}</ref><ref name="Boyer2009">{{cite book |last=Boyer |first=Mary Jo |title=Math for Nurses: A Pocket Guide to Dosage Calculation and Drug Preparation |url=https://books.google.com/books?id=FCfCGwqNt4QC|edition=7th |year=2009 |publisher=[[Wolters Kluwer Health]] {{pipe}} [[Lippincott Williams & Wilkins]] |location=Philadelphia, PA |isbn=978-0-7817-6335-6 |oclc=181600928 |pages=108–9 |chapter=UNIT 2 Measurement Systems: The Apothecary System |chapter-url=https://books.google.com/books?id=FCfCGwqNt4QC&pg=PA108 }}</ref>
{| class="wikitable" style="margin-right:0"
|+ Table of British apothecaries' volume units{{refn|group=nb|References for the [[#British apothecaries' volume measures|Table of British apothecaries' volume units]]: ''Unit'' column;<ref name="RoyalCollege1850">{{cite book |author=Royal College of Physicians of Dublin |author-link=Royal College of Physicians of Ireland |title=The Pharmacopœia of the King and Queen's College of Physicians in Ireland |year=1850 |publisher=Hodges and Smith |location=Dublin |oclc=599509441 |page=xlvi |chapter=Weights and Measures |hdl=2027/mdp.39015069402942 }}</ref><ref name="NIST">National Institute of Standards and Technology (October 2011). Butcher, Tina; Cook, Steve; Crown, Linda et al. eds. [https://www.nist.gov/pml/wmd/pubs/upload/AppC-12-hb44-final.pdf "Appendix C – General Tables of Units of Measurement"] (PDF). [http://physics.nist.gov/cuu/pdf/sp811.pdf ''Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices'']. NIST Handbook. '''44''' (2012 ed.). Washington, D.C.: US Department of Commerce, Technology Administration, National Institute of Standards and Technology. [[International Standard Serial Number|ISSN]] [http://www.worldcat.org/issn/0271-4027 0271-4027]. [[Online Computer Library Center|OCLC]] {{OCLC|58927093}}. Retrieved 6 July 2012.</ref>{{rp|C-7}}<ref name="Rowlett2001">{{cite web |url=http://www.unc.edu/~rowlett/units/dictF.html |title=F |first=Russ |last=Rowlett |date=13 September 2001 |work=How Many? A Dictionary of Units of Measurement |publisher=[[University of North Carolina at Chapel Hill]] |location=Chapel Hill, NC |at=fluid dram or fluidram (fl dr) |access-date=6 July 2012}}</ref> ''Symbols & abbreviations'' column;<ref name="Zentz2010" /><ref name="Boyer2009" /><ref name="RoyalCollege1850" /><ref name="NIST" />{{rp|C-5, C-17–C-18}}<ref name="Rowlett2001" /><ref name="Buchholz2009">{{cite book |last1=Buchholz |first1=Susan |last2=Henke |first2=Grace |title=Henke's Med-Math: Dosage Calculation, Preparation and Administration |url=https://books.google.com/books?id=ZlKqGHGNrtIC|edition=6th |year=2009 |publisher=[[Wolters Kluwer Health]] {{pipe}} [[Lippincott Williams & Wilkins]] |location=Philadelphia, PA |isbn=978-0-7817-7628-8 |oclc=181600929 |page=55 |chapter=Chapter 3: Metric, Apothecary, and Household Systems of Measurement – Table 3-1: Apothecary Abbreviations |chapter-url=https://books.google.com/books?id=ZlKqGHGNrtIC&pg=PA55 }}</ref><ref name="PickarEtAl2012">{{cite book |last1=Pickar |first1=Gloria D. |last2=Swart |first2=Beth |last3=Graham |first3=Hope |last4=Swedish |first4=Margaret |title=Dosage Calculations |url=https://books.google.com/books?id=wFEsup6KhuQC|edition=2nd Canadian |year=2012 |publisher=Nelson Education |location=Toronto |isbn=978-0-17-650259-1 |oclc=693657704 |page=528 |chapter=Appendix B: Apothecary System of Measurement – Apothecary Units of Measurement and Equivalents |chapter-url=https://books.google.com/books?id=wFEsup6KhuQC&pg=PA528 }}</ref> ''Relative to previous'' column;<ref name="RoyalCollege1850" /><ref name="NIST" />{{rp|C-7}} ''Exact metric value'' column – fluid ounce, pint and gallon,<ref name="UnitsOfMeasurementRegulations1995">{{cite book |author1=United Kingdom |author-link1=United Kingdom |author2=Department of Trade and Industry |author-link2=Department of Trade and Industry (United Kingdom) |title=The Units of Measurement Regulations 1995 |url=http://www.legislation.gov.uk/uksi/1995/1804/made |access-date=1 July 2012 |year=1995 |publisher=[[HMSO]] |location=London |isbn=978-0-11-053334-6 |oclc=33237616 |at=Schedule: Relevant Imperial Units, Corresponding Metric Units and Metric Equivalents}}</ref> all other values calculated using value for fluid ounce and the ''Relative to previous'' column's values.}}

! Unit
! Symbols and abbreviations
! Relative to previous
! Exact metric value<ref group="note">The [[Vinculum (symbol)|vinculum]] over numbers (e.g. {{overline|3}}) represents a [[repeating decimal]].</ref>
|-
|align=center| [[Minim (unit)|minim]]
|align=center| ♏︎, [[File:Mx, a symbol for minim in the apothecaries' system.svg|13px]], m, m., min
|align=right|   ({{frac|9600}} pint)
|align=right| {{gaps|59.193|880|208{{overline|3}}|u=[[microlitre|µL]]}}
|-
|align=center| [[fluid scruple]]
|align=center| fl ℈, fl s
|align=right| 20 minims ({{frac|480}} pint)
|align=right| {{gaps|1.183|877|604|1{{overline|6}}|u=mL}}
|-
|align=center| [[Dram (unit)|fluid drachm]] (fluid dram, fluidram)
|align=center| ʒ, fl ʒ, fʒ, ƒ 3, fl dr
|align=right| 3 fluid scruples ({{frac|160}} pint)
|align=right| {{val|3.5516328125|u=mL}}
|-
|align=center| [[fluid ounce]]
|align=center| ℥, fl ℥, f℥, ƒ ℥, fl oz
|align=right| 8 fluid drachms
|align=right| {{val|28.4130625|u=mL}}
|-
|align=center| [[pint]]
|align=center| O, pt
|align=right| 20 fluid ounces
|align=right| {{val|568.26125|u=mL}}
|-
|align=center| [[gallon]]
|align=center| C, gal
|align=right| 8 pints
|align=right| {{gaps|4.54609|u=L}}
|-
|colspan=4|'''Note:''' {{Reflist|group=note}}
|}

=== Mass and weight ===
In the 19th and 20th centuries, the UK used three different systems for mass and weight.

* [[troy weight]], used for precious metals;
* [[avoirdupois]] weight, used for most other purposes; and
* [[apothecaries' weight]], now virtually unused since the metric system is used for all scientific purposes.

The distinction between [[mass versus weight|mass and weight]] is not always clearly drawn. Strictly a pound is a unit of mass, but it is commonly referred to as a weight. When a distinction is necessary, the term ''[[pound-force]]'' may refer to a unit of force rather than mass. The troy pound ({{val|373.2417216|u=g}}) was made the primary unit of mass by the 1824 Act and its use was abolished in the UK on 1 January 1879,<ref name="Britain1878">{{cite book|author=Great Britain|title=Statutes at large ...|url=https://books.google.com/books?id=v39KAAAAMAAJ&pg=PA308|year=1878|page=308}}</ref> with only the troy ounce ({{val|31.1034768|u=g}}) and its [[decimal]] subdivisions retained.<ref name="Chisholm1911">{{cite book|last=Chisholm|first=Hugh|author-link=Hugh Chisholm|title=The Encyclopædia Britannica: A Dictionary of Arts, Sciences, Literature and General Information|url=https://books.google.com/books?id=qzkEAAAAYAAJ&pg=PA480|year=1911|publisher=At the University Press|page=480}}</ref> The ''Weights and Measures Act 1855'' (18 & 19 Victoria C72) made the avoirdupois pound the primary unit of mass.<ref name="Britain1855">{{cite book|author=Great Britain|title=A collection of public general statutes passed in the 18th and 19th years of the reign of Her Majesty Queen Victoria|url=https://books.google.com/books?id=L1YMAQAAMAAJ&pg=PA273|year=1855|pages=273–75}}</ref> In all the systems, the fundamental unit is the [[Pound (mass)|pound]], and all other units are defined as fractions or multiples of it.

{| class="wikitable" style="margin-right:0"
|+ Table of mass units
! Unit
! Pounds
! Grams
! Kilograms
! Notes
|-
|align=center| ''[[Grain (mass)|grain]]'' (gr)
|align=right| {{frac|{{val|7000}}}}
|align=right| {{val|0.06479891}}
|align=right|
|Exactly {{val|64.79891}} milligrams.
|-
|align=center| ''[[Dram (unit)|drachm]]'' (dr)
|align=right| {{frac|256}}
|align=right| {{val|1.7718451953125}}
|align=right|
| A dram is {{frac|16}} of an ounce
|-
|align=center| ''[[ounce]]'' (oz)
|align=right| {{frac|16}}
|align=right| {{val|28.349523125}}
|align=right|
| An ounce is {{frac|16}} of a pound
|-
|align=center| ''[[Pound (mass)|pound]]'' (lb)
|align=right| 1
|align=right| {{val|453.59237}}
|align=right| {{val|0.45359237}}
|Defined by The Units of Measurement Regulations 1994<ref>{{Cite web|url=http://www.legislation.gov.uk/uksi/1994/2867/schedule/made|title=The Units of Measurement Regulations 1994|website=legislation.gov.uk|language=en|access-date=2019-03-13}}</ref>
|-
|align=center| ''[[Stone (Imperial mass)|stone]]'' (st)
|align=right| 14
|align=right| {{val|6350.29318}}
|align=right| {{val|6.35029318}}
|The plural ''stone'' is often used when providing a weight (e.g. "this sack weighs 8 stone").<ref name=":0">{{Cite web|title = Definition of stone in English from the Oxford dictionary|url = http://www.oxforddictionaries.com/definition/english/stone|website = www.oxforddictionaries.com|publisher = Oxford University Press|access-date = 2015-11-25|ref = stonedefinition}}</ref> A person's weight is usually quoted in stone and pounds in English-speaking countries that use the avoirdupois system, with the exception of the United States and Canada, where it is usually quoted in pounds.
|-
|align=center| ''[[quarter (unit)|quarter]]'' (qr or qtr)
|align=right| 28
|align=right|
|align=right| {{val|12.70058636}}
|{{anchor|qtr}} One quarter (literally a quarter of a hundredweight) is equal to two stone or 28 pounds. The term ''quarter'' is also used in retail contexts, where it refers to four ounces, i.e. a quarter of a pound. (The 1824 Act defined a quarter as a unit of volume, as above: thus a 'quarter of wheat', 64 gallons, would weigh about 494 lb.<ref>{{cite web|url=https://www.engineeringtoolbox.com/foods-materials-bulk-density-d_1819.html | title= Bulk densities of some common food products | website= engineeringtoolbox.com | access-date = 19 January 2020}} The density of wheat is 0.770, and 291*0.770={{convert|224|kg}}.</ref>).
|-
|align=center| ''[[hundredweight]]'' (cwt)
|align=right| 112
|align=right|
|align=right| {{val|50.80234544}}
|One imperial hundredweight is equal to eight stone. This is the ''long hundredweight'', 112 pounds, as opposed to the short hundredweight of 100 pounds used in the United States and Canada.<ref name="justice1">''[http://laws-lois.justice.gc.ca/eng/acts/W-6/page-15.html/ Weights and Measures Act] {{Webarchive|url=https://web.archive.org/web/20121016084035/http://laws-lois.justice.gc.ca/eng/acts/W-6/page-15.html/ |date=16 October 2012 }}''</ref>
|-
|align=center| ''[[long ton|ton]]'' (t)
|align=right| 2240
|align=right|
|align=right| {{val|1016.0469088}}
|Twenty hundredweight equals a ton (as in the US and Canadian<ref name="justice1"/> systems). The imperial hundredweight is 12% greater than the US and Canadian one. The imperial ton (or ''long ton'') is {{val|2240}} pounds, which is much closer to a [[tonne]] (about {{val|2204.6}} pounds), compared to the 10.7% smaller North American ''short ton'' of {{convert|2000|lb|kg|3|comma=gaps}}.
|-
| style="text-align:center;" colspan="6"| '''Gravitational units'''
|- valign=top
|align=center|''[[slug (unit)|slug]]'' (slug)
|align=right| {{val|32.17404856}}
|align=right| {{val|14593.90294}}
|align=right| {{val|14.59390294}}
|The slug, a unit associated with imperial and US customary systems, is a mass that accelerates by 1 ft/s2 when a force of one [[pound (force)|pound]] (lbf) is exerted on it.<ref>{{cite web|url=http://www.wolframalpha.com/input/?i=Slug&a=*C.Slug-_*Unit-|title=Wolfram-Alpha: Computational Knowledge Engine}}</ref>
::{|
|-
| ||align=right| ''F'' ||= ''ma'' ([[Newton's second law]])
|-
| ||align=right| 1 lbf ||= 1 slug × 1 ft/s2 (as defined above)
|-
| ||align=right| 1 lbf ||= 1 lb × [[standard gravity|''g'']]/gc (by definition of the pound force{{citation needed|date=October 2017}})
|-
| ||align=right| ''g'' ||≈ {{val|32.17404856}} ft/s2
| ||align=right| ''gc'' ||≈ {{val|32.17404856}} lbm.ft/lbf.s2
|-
|∴ ||align=right| 1 slug ||≈ {{val|32.17404856}} pounds
|}
|}

== Natural equivalents ==
The 1824 Act of Parliament defined the yard and pound by reference to the [[prototype]] standards, and it also defined the values of certain [[physical constants]], to make provision for re-creation of the standards if they were to be damaged. For the yard, the length of a [[pendulum]] beating [[second]]s at the latitude of Greenwich at [[Mean Sea Level]] ''in vacuo'' was defined as {{val|39.01393}} inches. For the pound, the mass of a cubic inch of distilled water at an [[atmospheric pressure]] of 30 [[inches of mercury]] and a temperature of 62° [[Fahrenheit]] was defined as 252.458 grains, with there being 7,000 grains per pound.<ref name="google339" />

Following the destruction of the original prototypes in the [[Burning of Parliament|1834 Houses of Parliament fire]], it proved impossible to recreate the standards from these definitions, and a new [[Weights and Measures Acts of 1878 to 1893|Weights and Measures Act]] (18 & 19 Victoria. Cap. 72) was passed in 1855 which permitted the recreation of the prototypes from recognized [[Standard (metrology)|secondary standards]].<ref name="Britain1855" />

== Relation to other systems ==
[[File:English Length Units Graph.svg|thumb|English units of length|257x257px]]

The imperial system is one of many systems of [[English units]]. Most of the units are defined in more than one system, and some subsidiary units were used to a much greater extent, or for different purposes, in one area rather than another. The distinctions between the systems are often not drawn precisely.

One such distinction is that between the imperial system and older British/English units/systems or newer additions. The term ''imperial'' should not be applied to English units that were outlawed by the [[Weights and Measures Act 1824]] or earlier, or which had fallen out of use by that time, nor to post-imperial inventions, such as the [[slug (unit)|slug]] or [[poundal]].

The [[United States customary units|US customary system]] is derived from those English units which were in use at the time of the original settlement of North America from England in the 17th century. And because the United States had achieved independence from Britain prior to the 19th century, US customary units were unaffected by Britain's introduction of the imperial system in 1824.

== Current use ==
=== United Kingdom ===
{{see also|Metrication in the United Kingdom}}
[[File:Metric_and_imperial_systems_(2019).svg|thumb|Countries using the [[Metric system|metric]], imperial and [[US customary]] systems as of 2019]]
Since the [[Weights and Measures Act 1985]], British law defines base imperial units in terms of their metric equivalent. The metric system is routinely used in business and technology within the United Kingdom, with imperial units remaining in widespread use amongst the public.<ref name="BBCNews December 2011">{{cite news|title=Will British people ever think in metric?|url=https://www.bbc.co.uk/news/magazine-16245391|access-date=26 February 2017|publisher=BBC|date=21 December 2011|first=Jon|last=Kelly|quote=...but today the British remain unique in Europe by holding onto imperial weights and measures. ...the persistent British preference for imperial over metric is particularly noteworthy...}}</ref> All UK roads use the imperial system except for weight limits, and newer height or width restriction signs give metric alongside imperial.<ref name="BBCNews November 2014">{{cite news|title=Height and width road signs to display metric and imperial|url=https://www.bbc.com/news/uk-29965935|access-date=26 February 2017|publisher=BBC|date=8 November 2014 |quote=New road signs showing height and width restrictions will use both metric and imperial measurements from March 2015....Road signs for bridges, tunnels and narrow roads can currently show measurements in just feet and inches or only metres. Some already display both.}}</ref>[[File:MetricImperialUSCustomaryUnits.jpg|thumb|upright|A baby bottle that measures in three measurement systems—metric, imperial (UK), and US customary]]
Traders in the UK may accept requests from customers specified in imperial units, and scales which display in both unit systems are commonplace in the retail trade. Metric price signs may be accompanied by imperial price signs provided that the imperial signs are no larger and no more prominent than the metric ones.

The United Kingdom completed its official partial transition to the metric system in 1995, with imperial units still legally mandated for certain applications such as draught beer and cider,<ref name="WMbeer">{{cite web |url=http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1073792198 |archive-url=https://web.archive.org/web/20110720114311/http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1073792198 |archive-date=2011-07-20 |title=BusinessLink: Weights and measures: Rules for pubs, restaurants and cafes|access-date=24 August 2009|format=online |publisher= Department for Business, Innovation & Skills }}</ref> and road-signs.<ref name="WMroads">{{cite web |url=http://www.bwmaonline.com/Transport%20-%20DfT%20memo.htm |title=Department for Transport statement on metric road signs |access-date=24 August 2009|date=12 July 2002 |format=online |publisher=BWMA }}</ref> Therefore, the speedometers on vehicles sold in the UK must be capable of displaying miles per hour. Even though the [[troy weight|troy pound]] was outlawed in the UK in the Weights and Measures Act of 1878, the ''troy ounce'' ''may'' still be used for the weights of precious stones and metals. The original railways (many built in the Victorian era) are a big user of imperial units, with distances officially measured in miles and yards or miles and [[chain (length)|chains]], and also feet and inches, and speeds are in miles per hour.

Most British people still use imperial units in everyday life for distance (miles, yards, feet, and inches) and volume in some cases (especially milk and beer in pints) but rarely for canned or bottled soft drinks or petrol.<ref name="BBCNews December 2011"/><ref>{{cite news|work=The Guardian |date=1 December 2006|title=In praise of ... metric measurements|url=https://www.theguardian.com/commentisfree/2006/dec/01/comment.britishidentity | location=London | access-date=29 October 2017}}</ref> {{As of|February 2021}}, many British people also still use imperial units in everyday life for body weight (stones and pounds for adults, pounds and ounces for babies).<ref>{{cite web |url=https://moneyweek.com/economy/uk-economy/602705/decimalisation-britains-new-pence-turn-50-years-old |title=Decimalisation: Britain's "new pence" turn 50 years old |last=King |first=Max |date=15 February 2021 |work=MoneyWeek |access-date=8 April 2021}}</ref> Government documents aimed at the public may give body weight and height in imperial units as well as in metric.<ref>{{cite web|title=BMI healthy weight calculator |url= http://www.nhs.uk/Tools/Documents/BMI%20Healthy%20weight%20calculator.htm |publisher=[[National Health Service]] |access-date=25 November 2015}}</ref> A survey in 2015 found that many people did not know their body weight or height in both systems.<ref>{{Cite web |access-date=29 October 2017|date = 20 June 2015 |first1=Will |last1=Dahlgreen|url= https://yougov.co.uk/news/2015/06/20/britains-metric-muddle/ |title=Britain's metric muddle not changing any time soon|quote=even today [2015] most 18-24-year-olds still do not know how much they weigh in kilograms (60%) or how tall they are in metres and centimetres (54%). }}</ref> People under the age of 40 preferred the metric system but people aged 40 and over preferred the imperial system.<ref>{{Cite web |access-date=29 October 2017|date = 2015 |url= https://d25d2506sfb94s.cloudfront.net/cumulus_uploads/document/vsi5u7fi74/InternalResults_150609_systems_of_measurement_Website.pdf|title=YouGov Survey Results }}</ref> As in other English-speaking countries, including [[Australia]], [[Canada]] and the [[United States]], the height of horses is usually measured in [[Hand (unit)|hands]], standardised to {{Convert|4|in|sigfig=3}}. Fuel consumption for vehicles is commonly stated in miles per gallon (mpg), though official figures always include litres per {{Val|100|u=km}} equivalents and fuel is sold in litres. When sold [[draught beer|draught]] in licensed premises, beer and cider must be sold in pints, half-pints or third-pints.<ref>{{Cite web|url=https://www.gov.uk/weights-measures-and-packaging-the-law/specified-quantities|title=Weights and measures: the law|date=7 April 2020|website=gov.uk}}</ref> Cow's milk is available in both litre- and pint-based containers in supermarkets and shops. Areas of land associated with farming, forestry and real estate are commonly advertised in acres and square feet but, for contracts and [[land registration]] purposes, the units are always hectares and square metres.<ref name="legislation_20093045">{{Cite web| url= http://www.legislation.gov.uk/uksi/2009/3045/pdfs/uksiem_20093045_en.pdf | year = 2009 | title = Explanatory memorandum to The weights and measures (metrication amendments) regulations 2009|publisher= [[Legislation.gov.uk]]}} See paragraph 7.4.</ref>

Office space and industrial units are usually advertised in square feet. Steel pipe sizes are sold in increments of inches, while copper pipe is sold in increments of millimetres. Road bicycles have their frames measured in centimetres, while off-road bicycles have their frames measured in inches. [[Display size]]s for screens on television sets and computer monitors are always [[diagonal]]ly measured in inches. Food sold by length or width, e.g. pizzas or sandwiches, is generally sold in inches. Clothing is always sized in inches, with the metric equivalent often shown as a small supplementary indicator. Gas is usually measured by the cubic foot or cubic metre, but is billed like electricity by the [[kilowatt hour]].<ref>{{cite web|url=https://www.gov.uk/guidance/gas-meter-readings-and-bill-calculation|title=Gas meter readings and bill calculation|website=gov.uk}}</ref>

Pre-packaged products can show both metric and imperial measures, and it is also common to see imperial pack sizes with metric only labels, e.g. a {{cvt|1|lb|g|0}} tin of Lyle's Golden Syrup is always labelled {{Val|454|u=g}} with no imperial indicator. Similarly most jars of jam and packs of sausages are labelled {{Val|454|u=g}} with no imperial indicator.

===India===
[[India]] began converting to the metric system from the imperial system between 1955 and 1962. The metric system in weights and measures was adopted by the [[Indian Parliament]] in December 1956 with the ''Standards of Weights and Measures Act'', which took effect beginning 1 October 1958. For the next five years, both the previous and new system were legal. In April 1962, all other systems were banned.{{citation needed|date=August 2020}}

Today all official measurements are made in the metric system. In common usage some older Indians may still refer to imperial units. Some measurements, such as the heights of mountains, are still recorded in feet. Tyre rim diameters are still measured in inches, as used worldwide. Industries like the construction and the real estate industry still use both the metric and the imperial system though it is more common for sizes of homes to be given in square feet and land in acres.<ref name="Acharya, Anil Kumar 1958">Acharya, Anil Kumar. ''History of Decimalisation Movement in India'', Auto-Print & Publicity House, 1958.</ref>

In [[Indian English|Standard Indian English]], as in [[Australian English|Australian]], [[Singaporean English|Singaporean]], and [[British English]], metric units such as the litre, metre, and [[tonne]] utilise the traditional spellings brought over from [[French language|French]], which differ from those used in the [[American English|United States]] and the [[Philippine English|Philippines]]. The imperial long ton is invariably spelt with one 'n'.<ref name="Acharya, Anil Kumar 1958"/>

===Hong Kong===

[[Hong Kong]] has three main systems of [[units of measurement]] in current use:

* The [[Chinese units of measurement]] of the [[Qing Empire]] (no longer in widespread use in China);
* British imperial units; and
* The [[metric system]].

In 1976 the [[Hong Kong Government]] started the conversion to the metric system, and as of 2012 measurements for government purposes, such as road signs, are almost always in metric units. All three systems are officially permitted for trade,<ref name="Ordinance">{{cite web|url=http://www.hklii.hk/eng/hk/legis/ord/68/sch2.html|title=CAP 68 WEIGHTS AND MEASURES ORDINANCE Sched 2 UNITS OF MEASUREMENT AND PERMITTED SYMBOLS OR ABBREVIATIONS OF UNITS OF MEASUREMENT LAWFUL FOR USE FOR TRADE}}</ref> and in the wider society a mixture of all three systems prevails.

The Chinese system's most commonly used units for length are {{lang|zh|里}} (''lei5''), {{lang|zh|丈}} (''zoeng6''), {{lang|zh|尺}} (''[[Chi (unit)|cek3]]''), {{lang|zh|寸}} (''[[tsun|cyun3]]''), {{lang|zh|分}} (''fan1'') in descending scale order. These units are now rarely used in daily life, the imperial and metric systems being preferred. The imperial equivalents are written with the same basic Chinese characters as the Chinese system. In order to distinguish between the units of the two systems, the units can be prefixed with "Ying" ({{lang|zh|英}}, ''jing1'') for the imperial system and "Wa" ({{lang|zh|華}}, ''waa4'') for the Chinese system. In writing, derived characters are often used, with an additional {{lang|zh|口}} (mouth) [[Kangxi radicals|radical]] to the left of the original Chinese character, for writing imperial units. The most commonly used units are the [[mile]] or "li" ({{lang|zh|哩}}, ''li1''), the [[yard]] or "ma" ({{lang|zh|碼}}, ''maa5''), the [[Foot (unit)|foot]] or "chek" ({{lang|zh|呎}}, ''cek3''), and the [[inch]] or "tsun" ({{lang|zh|吋}}, ''cyun3'').

The traditional measure of flat area is the square foot ({{lang|zh|方呎, 平方呎}}, ''fong1 cek3, ping4 fong1 cek3'') of the imperial system, which is still in common use for real estate purposes. The measurement of agricultural plots and fields is traditionally conducted in {{lang|zh|畝}} (''mau5'') of the Chinese system.

For the measurement of volume, Hong Kong officially uses the metric system, though the gallon ({{lang|zh|加侖}}, ''gaa1 leon4-2'') is also occasionally used.

=== Canada ===
{{See also|Metrication in Canada}}
[[File:GasCan.jpg|thumb|upright|A one US gallon gas can purchased near the US-Canada border showing equivalences in imperial gallons and litres]]
[[File:Canadian canned food labels showing imperial and metric units of measurement.jpg|thumb|Imperial and metric measurements on Canadian canned goods labels. The imperial measurements often take precedence over the metric ones on labels.]]
During the 1970s, the metric system and SI units were introduced in Canada to replace the imperial system. Within the government, efforts to implement the metric system were extensive; almost any agency, institution, or function provided by the government uses SI units exclusively. Imperial units were eliminated from all public road signs and both systems of measurement will still be found on privately owned signs, such as the height warnings at the entrance of a [[Multi-storey car park|parkade]]. In the 1980s, momentum to fully convert to the metric system stalled when the government of [[Brian Mulroney]] was elected. There was heavy opposition to metrication and as a compromise the government maintains legal definitions for and allows use of imperial units as long as metric units are shown as well.<ref>{{cite web|url=http://laws.justice.gc.ca/en/showdoc/cs/W-6/sc:2//en#anchorsc:2 |title=Weights and Measures Act: Canadian units of measure |publisher=Justice Canada |access-date=14 November 2007 |url-status=dead|archive-url=https://web.archive.org/web/20110605042528/http://laws.justice.gc.ca/en/showdoc/cs/W-6/sc%3A2//en |archive-date=5 June 2011}}</ref><ref>
{{cite book
|chapter-url=http://www.inspection.gc.ca/english/fssa/labeti/guide/ch11e.shtml#11.2
|title=Guide to Food Labelling and Advertising
|chapter=11
|publisher=[[Canadian Food Inspection Agency]]
|access-date=1 December 2007
|url-status=dead
|archive-url=https://web.archive.org/web/20080124081159/http://www.inspection.gc.ca/english/fssa/labeti/guide/ch11e.shtml
|archive-date=24 January 2008
}}</ref><ref>
{{cite web |url=http://lois-laws.justice.gc.ca/eng/regulations/C.R.C.,_c._417/ |title=Consumer Packaging and Labelling Regulations (C.R.C., c. 417) |access-date=15 November 2012 |publisher=Justice Canada, Legislative Services Branch}}</ref>
The law requires that measured products (such as fuel and meat) be priced in metric units and an imperial price can be shown if a metric price is present.<ref name="Canadian compromise">
{{cite web |url=http://archives.cbc.ca/clip.asp?page=1&IDLan=1&IDClip=10620&IDCat=345&IDCatPa=261 |title=A Canadian compromise |access-date=11 March 2008 |publisher=[[Canadian Broadcasting Corporation|CBC]] |date=30 January 1985 |archive-url=https://web.archive.org/web/20090116024023/http://archives.cbc.ca/clip.asp?page=1&IDLan=1&IDClip=10620&IDCat=345&IDCatPa=261 |archive-date=2009-01-16}}
</ref><ref name="Livre">
{{cite web |url=http://archives.radio-canada.ca/clip.asp?page=1&IDLan=0&IDClip=9378&IDCat=216&IDCatPa=151 |title=Les livres et les pieds, toujours présents (eng:The pounds and feet, always present) |access-date=11 March 2008 |publisher=5 sur 5, Société [[Radio-Canada]] |language=fr
}}</ref> There tends to be leniency in regards to fruits and vegetables being priced in imperial units only.
[[Environment Canada]] still offers an imperial unit option beside metric units, even though weather is typically measured and reported in metric units in the Canadian media. Some radio stations near the United States border (such as [[CIMX]] and [[CIDR-FM|CIDR]]) primarily use imperial units to report the weather. Railways in Canada also continue to use imperial units.

Imperial units are still used in ordinary conversation. Today, Canadians typically use a mix of metric and imperial measurements in their daily lives. The use of the metric and imperial systems varies by age. The older generation mostly uses the imperial system, while the younger generation more often uses the metric system. [[Quebec]] has implemented metrication more fully. {{citation needed |date=July 2019}} Newborns are measured in SI at hospitals, but the birth weight and length is also announced to family and friends in imperial units. Drivers' licences use SI units, though many English-speaking Canadians give their height and weight in imperial. In livestock auction markets, cattle are sold in dollars per [[hundredweight]] (short), whereas hogs are sold in dollars per hundred kilograms. Imperial units still dominate in recipes, construction, house renovation and gardening.<ref>{{cite web|url=http://www.bwmaonline.com/Imperial%20Origins.htm|title=Imperial Measures - The Origins|publisher=[[British Weights and Measures Association]]|website=BWMAOnline.com}}</ref><ref>{{cite news|url=https://www.pressreader.com/canada/national-post-latest-edition/20110222/283661116291286|title=Crepes worth savouring|work=[[National Post]]|via=PressReader.com|first=Amy|last=Rosen|date=23 February 2011}}</ref><ref>{{cite news|url=https://www.pressreader.com/canada/national-post-national-edition/20110201/283403418230709|title=Scoring brownie points|work=[[National Post]]|via=PressReader.com|first=Amy|last=Rosen|date=2 February 2011}}</ref><ref>{{cite news|url=https://nationalpost.com/news/drinking-school/wcm/f22ca2bc-5ad6-4a50-a8c9-eee40d832521|title=Drinking school|work=[[National Post]]|first=Adam|last=McDowell|date=28 February 2011}}</ref><ref>{{cite web|url=http://www.homehardware.ca/en/cat/index.htm/Building-Supplies/Building-Materials/Fence-Products/_/N-nthr4|title=Home Hardware - Building Supplies - Building Materials - Fence Products|access-date=5 March 2011|archive-url=https://web.archive.org/web/20110629070126/http://www.homehardware.ca/en/cat/index.htm/Building-Supplies/Building-Materials/Fence-Products/_/N-nthr4|archive-date=29 June 2011|url-status=dead}}</ref> Land is now surveyed and registered in metric units whist initial surveys used imperial units. For example, partitioning of farm land on the prairies in the late 19th and early 20th centuries was done in imperial units; this accounts for imperial units of distance and area retaining wide use in the [[Prairie Provinces]]. In English-speaking Canada commercial and residential spaces are mostly (but not exclusively) constructed using square feet, while in French-speaking Quebec commercial and residential spaces are constructed in metres and advertised using both square metres and square feet as equivalents. Carpet or flooring tile is purchased by the square foot, but less frequently also in square metres.<ref>[https://www.tripadvisor.com/Travel-g153339-c15311/Canada:Metric.System.html Canada: Metric System]</ref><ref>{{cite web|url=http://www.lapresse.ca/vivre/societe/201508/25/01-4895245-systeme-metrique-a-quand-le-virage-final.php|title=Système métrique: à quand le virage final?|first=Marie|last=Allard|work=LaPresse.ca|date=2015-08-25|language=fr}}</ref> Motor-vehicle fuel consumption is reported in both litres per {{Val|100|u=km}} and statute miles per imperial gallon,<ref>{{cite web|url=http://www.oee.nrcan.gc.ca/transportation/tools/fuelratings/ratings-search.cfm?attr=8|title=Fuel Consumption Ratings Search Tool - Conventional Vehicles|first=Government of Canada, Natural Resources|last=Canada|access-date=15 January 2009|archive-date=6 July 2011|archive-url=https://web.archive.org/web/20110706181822/http://www.oee.nrcan.gc.ca/transportation/tools/fuelratings/ratings-search.cfm?attr=8|url-status=dead}}</ref> leading to the erroneous impression that Canadian vehicles are 20% more fuel-efficient than their apparently identical American counterparts for which fuel economy is reported in statute miles per US gallon (neither country specifies which gallon is used). Canadian railways maintain exclusive use of imperial measurements to describe train length (feet), train height (feet), capacity ([[Short ton|tons]]), speed (mph), and trackage (miles).<ref>{{cite web|url=http://www.tsb.gc.ca/eng/rapports-reports/rail/1996/r96w0171/r96w0171.asp|title=Railway Investigation Report R96W0171|first=Government of Canada, Transportation Safety Board of|last=Canada}}</ref>

Imperial units also retain common use in firearms and ammunition. Imperial measures are still used in the description of cartridge types, even when the cartridge is of relatively recent invention (e.g., [[.204 Ruger]], [[.17 HMR]], where the calibre is expressed in decimal fractions of an inch). Ammunition that is already classified in metric is still kept metric (e.g., [[9×19mm]]). In the manufacture of ammunition, bullet and powder weights are expressed in terms of [[grain (measure)|grains]] for both metric and imperial cartridges.

As in most of the western world, air navigation is based on ''nautical'' units, e.g., the nautical mile, which is neither imperial nor metric, though altitude is still measured in imperial feet<ref>{{cite web|url=http://www.langleyflyingschool.com/Pages/Canadian%20Aviation%20Regulations.html#Altimeter%20Rules|title=Canadian Aviation Regulations|website=Langley Flying School|at=sec. "Altimeter Rules"}}</ref> in keeping with the international standard.

===Australia===
{{Main|Metrication in Australia}}
While Metrication in Australia has largely ended the official use of imperial units, for particular measurements, international use of imperial units is still followed. In licensed venues, draught beer and cider is sold in glasses and jugs with [[beer in Australia#Sizes|sizes]] based on the imperial fluid ounce, though rounded to the nearest 5 mL.

* Newborns are measured in metric at hospitals, but the birth weight and length is also announced to family and friends in imperial units.
* Screen sizes, are frequently advertised in inches instead of or as well as centimetres.
* Property size is frequently advertised in acres, but is mostly as square metres.
* Navigation is done in nautical miles, and water-based speed limits are in nautical miles per hour.
* Advertising billboards are measured by feet because of the still pervading influence of the United States' practices on such activities.
* Historical writing and presentations may include pre-metric units to reflect the context of the era represented.
* The illicit drug trade in Australia still often uses imperial measurements, particularly when dealing with smaller amounts closer to end user levels e.g. "8-ball" an 8th of an ounce or {{Val|3.5|u=g}}; cannabis is often traded in ounces ("oz") and pounds ("p")
* Firearm barrel length are almost always referred by in inches, ammunition is also still measured in grain and ounces as well as grams.

As a result of cultural transmission of British and American English in Australia, there has also been noted to be a cause for residual use of imperial units of measure.

===New Zealand===
{{Main|Metrication in New Zealand}}
New Zealand introduced the metric system on 15 December 1976.<ref>[https://www.beehive.govt.nz/release/30-years-metric-system "30 Years of the Metric System"]</ref> Aviation was exempt, with altitude and airport elevation continuing to be measured in feet whilst navigation is done in [[nautical mile]]s; all other aspects (fuel quantity, aircraft weight, runway length, etc.) use metric units.

Screen sizes for devices such as televisions, monitors and phones, and wheel rim sizes for vehicles, are stated in inches, as is the convention in the rest of the world - and a 1992 study found a continued use of imperial units for birth weight and human height alongside metric units.<ref>[http://www.psychology.org.nz/cms_show_download.php?id=785 "Human use of metric measures of length"] {{webarchive |url=https://web.archive.org/web/20130209034410/http://www.psychology.org.nz/cms_show_download.php?id=785 |date=9 February 2013 }}. Dignan, J. R. E., & O'Shea, R. P. (1995). New Zealand Journal of Psychology, '''24''', 21–25.</ref>

===Ireland===
{{Main|Metrication in Ireland}}
{{unreferenced section|date=November 2019}}
Ireland has officially changed over to the metric system since entering the [[European Union]], with distances on new road signs being metric since 1997 and speed limits being metric since 2005. The imperial system remains in limited use – for sales of beer in pubs (traditionally sold by the pint). All other goods are required by law to be sold in metric units with traditional quantities being retained for goods like butter and sausages, which are sold in {{Convert|454|g|lb|0}} packaging. The majority of cars sold pre-2005 feature speedometers with miles per hour as the primary unit, but with a kilometres per hour display as well. Often signs such as those for bridge height can display both metric and imperial units. Imperial measurements continue to be used colloquially by the general population especially with height and distance measurements such as feet, inches, and acres as well as for weight with pounds and stones still in common use among people of all ages. Measurements such as yards have fallen out of favour with younger generations. Ireland's railways still use imperial measurements for distances and speed signage.<ref>{{Cite web|title=Republic of Ireland|url=http://www.railsigns.uk/overseas/ireland2/ireland2.html|access-date=2021-02-22|website=www.railsigns.uk}}</ref><ref>{{Cite web|last=Rail|first=Irish|title=Network Statement|url=https://www.irishrail.ie/en-ie/about-us/iarnrod-eireann-network-statement|url-status=live|access-date=2021-02-22|website=Irish Rail|language=en}}</ref> Property is usually listed in square feet as well as metres also.

Horse racing in Ireland still continues to use stones, pounds, miles and furlongs as measurements.<ref>http://www.hri-ras.ie/information-centre/hri-directives-and-rules/full/</ref>

===Bahamas===

Imperial measurements remain in general use in the [[Bahamas]]. This is unlikely to change due to the Bahamas' proximity to the United States.

One significant exception is in schools, where as a result of the British influeunce (UK exams were taken as school [[leaving exams]] until the 1990s) the metric system is used in science classes (biology, chemistry and physics) and in science textbooks.

Legally, both the imperial and metric systems are recognised by the Weights and Measures Act 2006.<ref>{{cite web |author1=Parliament of the Bahamas |title=Weights and Measures Act 2006 |url=https://www.bbsq.bs/en/files/acts-and-regulations/1-weights-and-measures-act/file |website=Bahamas Bureau of Standards and Quality}}</ref>

===Other countries===
Some imperial measurements remain in limited use in [[Malaysia]], the [[Philippines]], [[Sri Lanka]] and [[South Africa]]. Measurements in feet and inches, especially for a person's height, are frequently encountered in conversation and non-governmental publications.

Prior to metrication, it was a common practice in Malaysia for people to refer to unnamed locations and small settlements along major roads by referring to how many miles the said locations were from the nearest major town. In some cases, these eventually became the official names of the locations; in other cases, such names have been largely or completely superseded by new names. An example of the former is Batu 32 (literally "Mile 32" in [[Malay language|Malay]]), which refers to the area surrounding the intersection between [[Malaysia Federal Route 22|Federal Route 22]] (the [[Tamparuli]]-[[Sandakan]] highway) and [[Malaysia Federal Route 13|Federal Route 13]] (the Sandakan-[[Tawau]] highway). The area is so named because it is 32 miles west of Sandakan, the nearest major town.

Petrol is still sold by the imperial gallon in [[Anguilla]], [[Antigua and Barbuda]], [[Belize]], [[Myanmar]], the [[Cayman Islands]], [[Dominica]], [[Grenada]], [[Montserrat]], [[St. Kitts and Nevis|St Kitts and Nevis]] and [[St. Vincent and the Grenadines]]. The [[United Arab Emirates]] Cabinet in 2009 issued the Decree No. (270 / 3) specifying that, from 1 January 2010, the new unit sale price for petrol will be the litre and not the gallon, which was in line with the UAE Cabinet Decision No. 31 of 2006 on the national system of measurement, which mandates the use of International System of units as a basis for the legal units of measurement in the country.<ref name="gas7">{{cite web|url=http://agriculture.gov.gd/newsitem.aspx?nid=375 |publisher=The Ministry of Agriculture, [[Government of Grenada]] |date=2004-11-01 |title=Address by Agriculture Minister Gregory Bowen |access-date=15 January 2008 |quote=The price of gasoline at the pumps was fixed at EC$7.50 per imperial gallon... |archive-url=https://web.archive.org/web/20080324183215/http://agriculture.gov.gd/newsitem.aspx?nid=375 |archive-date=24 March 2008 }}</ref><ref>{{cite web|url=http://mof.gov.bz/faqresults.asp?category=SUPPLIES+CONTROL&question=39 |title=FAQ |website=MoF.gov.bz |access-date=15 January 2008 |publisher=Belize Ministry of Finance |archive-url=https://web.archive.org/web/20080123210505/http://mof.gov.bz/faqresults.asp?category=SUPPLIES+CONTROL&question=39 |archive-date=2008-01-23 |quote=• Kerosene per US Gallon (per Imperial gallon) • Gasoline (Regular)(per imperial Gallon) • Gasoline (Premium) (per Imperial Gallon) • Diesel (per Imperial Gallon) }}</ref><ref name="gas5">{{cite web|url=http://www.antigua-barbuda.com/business_politics/budget_speeches/budget_speech_2001.asp |title=The High Commission Antigua and Barbuda |access-date=15 January 2008 |url-status=dead|archive-url=https://web.archive.org/web/20090131213551/http://www.antigua-barbuda.com/business_politics/budget_speeches/budget_speech_2001.asp |archive-date=31 January 2009}}</ref><ref>{{cite web|url=http://www.international-fuel-prices.com/downloads/FuelPrices2005.pdf |title=International Fuel Prices 2005 |website=International-Fuel-Prices.com |first=Gerhard P. |last=Metschies |date=6 September 2005 |access-date=15 January 2008 |page=96 |publisher=German Technical Cooperation |archive-url=https://web.archive.org/web/20070207130929/http://www.international-fuel-prices.com/downloads/FuelPrices2005.pdf |archive-date=2007-02-07}}</ref> Sierra Leone switched to selling fuel by the litre in May 2011.<ref>{{cite web|publisher=[[Sierra Leone]] Embassy in the United States|url=http://embassyofsierraleone.net/node/54|title=Introduction of the Metric System and the Price of Petroleum Products|archive-url=https://web.archive.org/web/20150429165159/http://embassyofsierraleone.net/node/54|archive-date=29 April 2015|access-date=23 October 2011}}</ref>

In October 2011, the Antigua and Barbuda government announced the re-launch of the Metrication Programme in accordance with the Metrology Act 2007, which established the International System of Units as the legal system of units. The Antigua and Barbuda government has committed to a full conversion from the imperial system by the first quarter of 2015.<ref>{{cite news|title=Minister Lovell Addresses Metric Conversions |url=http://www.caribarena.com/antigua/news/economy/98673-minister-lovell-addresses-metric-conversions.html |newspaper=CARIBARENA Antigua |date=18 October 2011 |access-date=23 October 2011 |url-status=dead|archive-url=https://web.archive.org/web/20111020040638/http://www.caribarena.com/antigua/news/economy/98673-minister-lovell-addresses-metric-conversions.html |archive-date=20 October 2011}}</ref>

== See also ==
{{commons category|British Imperial units}}
{{columns-list|colwidth=30em|
* [[Acre-foot]]
* [[Board foot]]
* [[Comparison of the imperial and US customary measurement systems]]
* [[Conversion of units]]
* [[Cooking weights and measures]]
* [[Cord (volume)]]
* [[History of measurement]]
* [[Metrication]]
* [[Systems of measurement]]
* [[Unit of measurement]]
* [[£sd]] (''L.s.d.'')
}}

==Notes==
{{reflist|group=nb}}

== References ==
{{Reflist|30em}}

== Sources ==
* Appendices B and C of [https://web.archive.org/web/20050403211923/http://ts.nist.gov/ts/htdocs/230/235/h442003.htm NIST Handbook 44]
* {{cite web |first1=A. |last1=Thompson |first2=Barry N. |last2=Taylor |url=http://physics.nist.gov/Pubs/SP811/ |title=The NIST guide for the use of the international system of units |publisher=NIST |date=5 October 2010 |access-date=15 October 2012 |others=also available as [http://physics.nist.gov/cuu/pdf/sp811.pdf a PDF file] |archive-url=https://web.archive.org/web/20100216211152/http://physics.nist.gov/Pubs/SP811/ |archive-date=16 February 2010 |url-status=dead}}
* 6 George IV chapter 12, 1825 (statute)

== External links ==
* [http://bwma.org.uk British Weights And Measures Association]
* [https://archive.is/20070224102425/http://laws.justice.gc.ca/en/ShowFullDoc/cs/W-6///en Canada Weights and Measures Act 1970-71-72]
* [https://web.archive.org/web/20061126120208/http://ts.nist.gov/WeightsAndMeasures/Publications/upload/h4402_appenc.pdf General table of units of measure – NIST – pdf]
* [http://www.unc.edu/~rowlett/units/ How Many? A Dictionary of Units of Measurement]
* {{UK SI|year=1995|number=1804|title=Units of Measurement Regulations 1995}}

{{Imperial units}}
{{systems of measurement}}

[[Category:Imperial units]]
[[Category:Customary units of measurement]]
[[Category:Systems of units]]
[[Category:1824 introductions]]

Wikipedia - Benutzerbeiträge [de]

Imperiales Einheitensystem