acre

One acre equals {{frac|1|640}} (0.0015625) square mile, 4,840 square yards, 43,560 square feet, or about {{convert|4047|m2|ha|abbr=off|lk=on|sigfig=4}} (see below). While all modern variants of the acre contain 4,840 square yards, there are alternative definitions of a yard, so the exact size of an acre depends upon the particular yard on which it is based. Originally, an acre was understood as a strip of land sized at forty perches (660 ft, or 1 furlong) long and four perches (66 ft) wide;{{cite book| last=Klein |first=Herbert Arthur |title=The Science of Measurement: A Historical Survey |url=https://books.google.com/books?id=CrmuSiCFyikC&pg=PA76 |year=2012 |publisher=Courier Corporation |isbn=978-0-486-14497-9 |page=76}} this may have also been understood as an approximation of the amount of land a yoke of oxen could plough in one day (a furlong being "a furrow long"). A square enclosing one acre is approximately 69.57 yards, or 208 feet 9 inches ({{convert|208.71|ft|m|abbr=off|disp=out}}), on a side. As a unit of measure, an acre has no prescribed shape; any area of 43,560 square feet is an acre.

In the international yard and pound agreement of 1959, the United States and five countries of the Commonwealth of Nations defined the international yard to be exactly 0.9144 metre.{{cite web |publisher= National Bureau of Standards |date= 25 June 1959 |url= http://geodesy.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf |title= Refinement of Values for the Yard and the Pound |website= noaa.gov |archive-url= https://archive.today/20200305184155/https://geodesy.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf |archive-date= 5 March 2020 |url-status= dead |access-date= 3 December 2006 }} The US authorities decided that, while the refined definition would apply nationally in all other respects, the US survey foot (and thus the survey acre) would continue 'until such a time as it becomes desirable and expedient to readjust [it]'. By inference, an "international acre" may be calculated as exactly {{gaps|4,046.856|422|4}} square metres but it does not have a basis in any international agreement.

Both the international acre and the US survey acre contain {{frac|640}} of a square mile or 4,840 square yards, but alternative definitions of a yard are used (see survey foot and survey yard), so the exact size of an acre depends upon the yard upon which it is based. The US survey acre is about 4,046.872 square metres; its exact value ({{sfrac|4046|13,525,426|15,499,969}} m²) is based on an inch defined by 1 metre = 39.37 inches exactly, as established by the Mendenhall Order of 1893.* {{cite journal |last=Mendenhall |first=T.C. |date=6 October 1922 |title=The United States Fundamental Standards of Length and Mass |journal=Science |series=New Series |volume=56 |issue=1449 |pages=337–380 |issn=0036-8075 |doi=10.1126/science.56.1449.377 |jstor=1647062 |pmid=17833047 |bibcode=1922Sci....56..377M |access-date=16 August 2021 |url=https://www.jstor.org/stable/1647062}} Surveyors in the United States use both international and survey feet, and consequently, both varieties of acre.National Geodetic Survey, (January 1991), [http://www.ngs.noaa.gov/INFO/Policy/st_plane.html Policy of the National Geodetic Survey Concerning Units of Measure for the State Plane Coordinate System of 1983].

Since the difference between the US survey acre and international acre (0.016 square metres, 160 square centimetres or 24.8 square inches), is only about a quarter of the size of an A4 sheet or US letter, it is usually not important which one is being discussed. Areas are seldom measured with sufficient accuracy for the different definitions to be detectable.[https://www.nsps.us.com/resource/resmgr/alta_standards/2021_Standards_20201030_grk.pdf Minimum Standard Detail Requirements For ALTA/NSPS Land Title Surveys]. Federick, MD: American Congress on Surveying and Mapping. 2021. [The stated maximum allowable "precision" (page 2) is 2 cm and 50 parts per million. An instrument consistently measuring 2 cm short would measure the area of a one international acre square, 63.614907 m on a side, as 4044.3 square metres, 2.6 square metres less than the true value, a far greater discrepancy than the difference between the international and survey acres.] In October 2019, the US National Geodetic Survey and the National Institute of Standards and Technology announced their joint intent to end the "temporary" continuance of the US survey foot, mile, and acre units (as permitted by their 1959 decision, above), with effect from the end of 2022.{{cite web |title=NGS and NIST to Retire U.S. Survey Foot after 2022 |url=https://www.ngs.noaa.gov/web/news/us-survey-foot.shtml |publisher=National Geodetic Survey |access-date=4 March 2020 |date=31 October 2019}}{{cite web |title=U.S. Survey Foot: Revised Unit Conversion Factors |url=https://www.nist.gov/pml/us-surveyfoot/revised-unit-conversion-factors |publisher=NIST |access-date=4 March 2020 |date=16 October 2019}}

The Puerto Rican cuerda ({{convert|1|cda|disp=out}}) is sometimes called the "Spanish acre" in the continental United States.[http://www.unc.edu/~rowlett/units/dictC.html Units: C: cuerda]. Russ Rowlett. The University of North Carolina at Chapel Hill.

The acre is commonly used in many current and former Commonwealth countries by custom, and in a few it continues as a statute measure. These include Antigua and Barbuda,{{cite web|url=http://www.antiguaobserver.com/govt-gifts-bakka-with-half-acre-land/|title=Gov't Gifts 'Bakka' With Half-Acre Land {{pipe}} Antigua Observer Newspaper|archive-url=https://web.archive.org/web/20131004213313/http://www.antiguaobserver.com/govt-gifts-bakka-with-half-acre-land/|archive-date=4 October 2013|url-status=dead|access-date=14 February 2014}} American Samoa,{{cite web|url=http://www.samoanews.com/?q=node/4505|title=National Park of American Samoa completes two successful forest projects {{pipe}} Samoa News|date=15 April 2012 |publisher=SamoaNews.com|access-date=14 February 2014}} The Bahamas,{{cite web |last1=Lowe |first1=Alison |title=Construction underway on Old Fort School |url=https://thenassauguardian.com/2013/08/15/construction-underway-on-old-fort-school/ |website=The Nassau Guardian |date=15 August 2013 |access-date=6 February 2019 |archive-date=25 April 2019 |archive-url=https://web.archive.org/web/20190425055105/https://thenassauguardian.com/2013/08/15/construction-underway-on-old-fort-school/ |url-status=dead }} Belize,{{cite web|url=http://amandala.com.bz/news/2225-acre-cobia-farm-proposed-near-lark-and-bugle-cayes/|title=2,225-acre Cobia farm proposed near Lark and Bugle Cayes {{pipe}} Amandala Newspaper|date=7 January 2008 |publisher=amandala.com.bz|access-date=14 February 2014}} the British Virgin Islands,{{cite web|url=http://www.bvibeacon.com/2/index.php?option=com_content&view=article&id=3051%3Awork-continues-on-development-&Itemid=1&showall=1|title=Work continues on development|publisher=bvibeacon.com|access-date=14 February 2014}}, Canada,{{cite web|url=https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=3210004701|title=Value per acre of farm land and buildings at July 1|date=13 April 2021 |publisher=Statistics Canada|access-date=11 March 2023}} the Cayman Islands,{{cite web|url=http://www.compasscayman.com/caycompass/2013/08/21/Kai-drama-over-50-acre-development/|title=Kai drama over 50-acre development :: cayCompass.com|publisher=compasscayman.com|access-date=14 February 2014|archive-date=1 March 2014|archive-url=https://web.archive.org/web/20140301003404/http://www.compasscayman.com/caycompass/2013/08/21/Kai-drama-over-50-acre-development/|url-status=dead}} Dominica,{{cite web|url=http://dominicanewsonline.com/news/homepage/news/agriculture/dominica-not-meeting-quota-in-banana-industry/|title=Dominica not meeting quota for international banana markets {{pipe}} Dominica News Online|publisher=dominicanewsonline.com|access-date=14 February 2014|archive-date=4 October 2013|archive-url=https://web.archive.org/web/20131004213258/http://dominicanewsonline.com/news/homepage/news/agriculture/dominica-not-meeting-quota-in-banana-industry/|url-status=dead}} the Falkland Islands,{{cite web|url=http://www.penguin-news.com/index.php/columns/28-farm-yarns-with-elaine/462-farm-yarns-with-elaine-turner-part-13|title=Farm Yarns with Elaine – Farm yarns with Elaine Turner – Part 13|publisher=penguin-news.com|archive-url=https://web.archive.org/web/20150924070635/http://www.penguin-news.com/index.php/columns/28-farm-yarns-with-elaine/462-farm-yarns-with-elaine-turner-part-13|archive-date=24 September 2015|url-status=dead|access-date=14 February 2014}} Grenada,{{cite web|url=http://www.grenadabroadcast.com/news/diaspora/14367-the-grenada-spices-industry|title=Grenada Broadcast – George Grant – The Grenada Spices Industry|publisher=grenadabroadcast.com|archive-url=https://web.archive.org/web/20131004215245/http://www.grenadabroadcast.com/news/diaspora/14367-the-grenada-spices-industry|archive-date=4 October 2013|url-status=dead|access-date=14 February 2014}} Ghana,{{Cite web|url=http://www.theafricareport.com/News-Analysis/mortgages-in-ghana-snapping-up-an-acre-of-accra-real-estate.html|title=Mortgages in Ghana: Snapping up an acre of Accra real estate |last=Ofori-Atta|first=Prince|website=www.theafricareport.com|language=en-gb|access-date=31 March 2018}} Guam,{{cite web|url=http://www.guampdn.com/article/20130824/NEWS01/308240022/Manamko-could-see-new-homes|title=Local News {{pipe}} Pacific Daily News|publisher=guampdn.com|archive-url=https://archive.today/20131001040155/http://www.guampdn.com/article/20130824/NEWS01/308240022/Manamko-could-see-new-homes|archive-date=1 October 2013|url-status=dead|access-date=14 February 2014}} the Northern Mariana Islands,{{cite web |title=Islan Pagan |url=http://www.saipantribune.com/newsstory.aspx?cat=15&newsID=126803 |website=saipantribune.com |archive-url=https://web.archive.org/web/20131017024119/http://www.saipantribune.com/newsstory.aspx?cat=15&newsID=126803 |archive-date=17 October 2013}} Jamaica,{{cite web|url=http://supremecourt.gov.jm/sites/default/files/judgments/Tropicrop%20Mushrooms%20Ltd%20v%20Saint%20Thomas%20Parish%20Council%2C%20etal.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://supremecourt.gov.jm/sites/default/files/judgments/Tropicrop%20Mushrooms%20Ltd%20v%20Saint%20Thomas%20Parish%20Council%2C%20etal.pdf |archive-date=9 October 2022 |url-status=live|title=Tropicrop Mushrooms Ltd v Saint Thomas Parish Council, etal}} Montserrat,{{cite web|url=http://www.themontserratreporter.com/beresford-allen-of-st-peters-montserrat-is-a-wanted-man/|title=Beresford Allen of St. Peters Montserrat is a Wanted Man! {{pipe}} The Montserrat Reporter|publisher=themontserratreporter.com|access-date=14 February 2014}} Samoa,{{cite web|url=http://www.samoaobserver.ws/local-news/politics/3110-conflicting-stories-about-nuu-estate|title=Conflicting stories about Nu'u estate|publisher=samoaobserver.ws|access-date=14 February 2014|archive-url=https://web.archive.org/web/20180919111736/http://www.samoaobserver.ws/local-news/politics/3110-conflicting-stories-about-nuu-estate|archive-date=19 September 2018|url-status=dead}} Saint Lucia,{{cite web|url=http://www.thevoiceslu.com/features/2008/july/12_07_08/The_Redevelopment_of_the_Union_Agricultural_Station.htm|title=The Voice – The national newspaper of St. Lucia since 1885|publisher=thevoiceslu.com|archive-url=https://web.archive.org/web/20131004215536/http://www.thevoiceslu.com/features/2008/july/12_07_08/The_Redevelopment_of_the_Union_Agricultural_Station.htm|archive-date=4 October 2013|url-status=dead|access-date=14 February 2014}} St. Helena,{{cite web|url=http://sthelenaonline.org/2012/09/02/feature-we-built-an-island-dream-on-our-own-st-helena/|title=FEATURE: We built an island dream on our own St Helena {{pipe}} St Helena Online|publisher=sthelenaonline.org|archive-url=https://web.archive.org/web/20131021090201/http://sthelenaonline.org/2012/09/02/feature-we-built-an-island-dream-on-our-own-st-helena/|archive-date=21 October 2013|url-status=dead|access-date=14 February 2014}} St. Kitts and Nevis,{{cite web|url=http://www.thestkittsnevisobserver.com/2013/06/14/passport-money.html|title=SIDF Sinks SKN Passport Money into Christophe Harbour :: The St. Kitts-Nevis Observer|publisher=thestkittsnevisobserver.com|archive-url=https://web.archive.org/web/20131004212924/http://www.thestkittsnevisobserver.com/2013/06/14/passport-money.html|archive-date=4 October 2013|url-status=dead|access-date=14 February 2014}} St. Vincent and the Grenadines,{{cite web|url=http://www.iwnsvg.com/2013/03/15/pmvows-to-spend-rest-of-life-seeking-reparations/|title=PM vows to spend rest of life seeking reparations – I-Witness News|date=15 March 2013 |publisher=iwnsvg.com|access-date=14 February 2014}} Turks and Caicos,{{cite web|url=http://suntci.com/government-gets-million-from-emerald-cay-sale-p402-106.htm|title=Government gets $8million from Emerald Cay sale|publisher=suntci.com|access-date=14 February 2014}} the United Kingdom, the United States, and the US Virgin Islands.{{cite web|url=http://m.virginislandsdailynews.com/news/proposed-dolphin-facility-will-enclose-about-2-acres-of-water-bay-1.1415178|title=Proposed dolphin facility will enclose about 2 acres of Water Bay – News – Virgin Islands Daily News|publisher=m.virginislandsdailynews.com|archive-url=https://web.archive.org/web/20131022220250/http://m.virginislandsdailynews.com/news/proposed-dolphin-facility-will-enclose-about-2-acres-of-water-bay-1.1415178|archive-date=22 October 2013|url-status=dead|access-date=14 February 2014}}

In the Republic of Ireland, the hectare is legally used under European units of measurement directives; however, the acre (the same standard statute as used in the UK, not the old Irish acre, which was of a different size) is still widely used, especially in agriculture.{{Cite web|url=https://www.farmersjournal.ie/hectacre-recognised-as-official-area-measurement-359167|title='Hectacre' recognised as official area measurement|website=www.farmersjournal.ie}}{{Cite web|url=https://www.farmersjournal.ie/what-is-an-acre-the-history-of-land-surveying-154946|title=What is an acre? The history of land surveying|website=www.farmersjournal.ie}}{{Cite web|url=https://www.irishexaminer.com/opinion/columnists/arid-20170714.html|title=Time to fully embrace the metric system|date=15 October 2011|website=Irish Examiner}}{{Cite web|url=https://usma.org/metrication-in-other-countries|title=Metrication in other countries – US Metric Association|website=usma.org}}

In India, residential plots are measured in square feet or square metre, while agricultural land is measured in acres.{{Cite web|date=17 April 2020|title=Land Measurement Units in India – Confident Group|url=https://www.confident-group.com/land-measurement-units-in-india/|access-date=19 October 2020|website=www.confident-group.com|language=en}} In Sri Lanka, the division of an acre into 160 perches or 4 roods is common.{{Cite web|date=27 July 2018|title=What is a perch of land in Sri Lanka?|url=https://www.ceylonestateagents.com/faqs/what-is-a-perch-of-land-in-sri-lanka|access-date=19 October 2020|language=en-GB}} In Pakistan, residential plots are measured in {{lang|ur-Latn|kanal}} (20 {{lang|ur-Latn|marla}} = 1 {{lang|ur-Latn|kanal}} = 605 sq yards) and open/agriculture land measurement is in acres (8 {{lang|ur-Latn|kanal}} = 1 acre) and {{lang|ur-Latn|muraba}} (25 acres = 1 {{lang|ur-Latn|muraba}} = 200 {{lang|ur-Latn|kanal}}), {{lang|ur-Latn|jerib, wiswa}} and {{lang|ur-Latn|gunta}}.{{Cite web |title=Murabba to Kanal Calculator {{!}} Convert Murabba to Kanal |url=https://housing.com/calculators/murabba-to-kanal |access-date=21 November 2024 |website=Housing |language=en}}{{Cite web |last=Rowlett |first=Russ |title=How Many? A Dictionary of Units of Measurement |url=https://www.unc.edu/~rowlett/units/dictK.html |url-status=dead |archive-url=https://web.archive.org/web/20080112120328/https://www.unc.edu/~rowlett/units/dictK.html |archive-date=12 January 2008 |access-date=21 November 2024 |website=University of North Carolina at Chapel Hill}}

Its use as a primary unit for trade in the United Kingdom ceased to be permitted from 1 October 1995, due to the 1994 amendment of the Weights and Measures Act,[http://www.legislation.gov.uk/uksi/1994/2866/schedule/made The Weights and Measures Act 1985 (Metrication) (Amendment) Order 1994] HM Government, 1995 where it was replaced by the hectare{{snd}} though its use as a supplementary unit continues to be permitted indefinitely.{{Cite web| url= http://www.legislation.gov.uk/uksi/2009/3045/pdfs/uksiem_20093045_en.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.legislation.gov.uk/uksi/2009/3045/pdfs/uksiem_20093045_en.pdf |archive-date=9 October 2022 |url-status=live | year = 2009 | title = Explanatory memorandum to The weights and measures (metrication amendments) regulations 2009|publisher= Legislation.gov.uk}} This was with the exemption of land registration, which records the sale and possession of land;{{cite web| title=Land Registration Act 2002 | url=https://www.legislation.gov.uk/ukpga/2002/9/contents | website= legislation.gov.uk | publisher=The National Archives | location=UK | year=2002 | access-date=3 August 2018}} in 2010 HM Land Registry ended its exemption. The measure is still used to communicate with the public,{{cite web |url=https://waddesdon.org.uk/about-us/waddesdon-estate/ |publisher=Waddesdon Manor |title=About us. Waddesdon Estate |quote=By purchasing the adjoining land, the estate has grown from the original 2,700 acres in 1874 to 6,000 acres in 2011.}} and informally (non-contract) by the farming and property industries.{{cite web|title= Outlook and historical context|url = https://www.savills.co.uk/research_articles/229130/228020-0A|publisher=Savills|date= 12 February 2018}}{{cite news|title=Amount of UK farmland put up for sale shrinks as prices fall|date=13 February 2018|newspaper=Financial Times|url=https://www.ft.com/content/bce30bee-1016-11e8-8cb6-b9ccc4c4dbbb |archive-url=https://ghostarchive.org/archive/20221210/https://www.ft.com/content/bce30bee-1016-11e8-8cb6-b9ccc4c4dbbb |archive-date=10 December 2022 |url-access=subscription |url-status=live}}{{cite web|url=https://www.farminguk.com/farmsandlandforsale|title=Land for Sale|website=farminguk}}

File:Acre superimposed over football fields.svg field (green) and association football/soccer pitch (blue)]]

1 international acre is equal to the following metric units:

• 0.40468564224 hectare (A square with 100 m sides has an area of 1 hectare.)
• 4,046.8564224 square metres (or a square with approximately 63.61 m sides)

1 United States survey acre is equal to:

• 0.404687261 hectare
• 4,046.87261 square metres (1 square kilometre is equal to 247.105 acres)

1 acre (both variants) is equal to the following customary units:

• 66 feet × 660 feet (43,560 square feet)
• 10 square chains (1 chain = 66 feet = 22 yards = 4 rods = 100 links)
• 1 acre is approximately 208.71 feet × 208.71 feet (a square)
• 4,840 square yards
• 43,560 square feet
• 160 perches. A perch is equal to a square rod (1 square rod is 0.00625 acre)
• 4 roods
• A furlong by a chain (furlong 220 yards, chain 22 yards)
• 40 rods by 4 rods, 160 rods² (historically fencing was often sold in 40 rod lengths{{Cite journal|date=1919|title=ed. 842|journal=Farmers' Bulletin|publisher=U.S. Government Printing Office|page=24}})
• {{frac|1|640}} (0.0015625) square mile (1 square mile is equal to 640 acres)

Perhaps the easiest way for US residents to envision an acre is as a rectangle measuring 88 yards by 55 yards ({{frac|1|10}} of 880 yards by {{frac|1|16}} of 880 yards), about {{frac|9|10}} the size of a standard American football field. To be more exact, one acre is 90.75% of a 100-yd-long by 53.33-yd-wide American football field (without the end zone). The full field, including the end zones, covers about {{convert|1.32|acres|2|abbr=on}}. For residents of other countries, the acre might be envisioned as rather more than half of a {{convert|1.76|acres|2|abbr=on}} football pitch.

{{Anthropic_Farm_Units}}

The word acre is derived from the Norman, attested for the first time in a text of Fécamp in 1006 to the meaning of «agrarian measure».{{cite web |last1=CNTRL | title=Portail Lexical - Etymologie de acre |url=https://archive.wikiwix.com/cache/index2.php?url=https%3A%2F%2Fwww.cnrtl.fr%2Fetymologie%2Facre#federation=archive.wikiwix.com&tab=url}} Acre dates back to the old Scandinavian akr “cultivated field, ploughed land” which is perpetuated in Icelandic and the Faroese {{lang|de|akur}} “field (wheat)”, Norwegian and Swedish {{lang|de|åker}}, Danish {{lang|de|ager}} “field”, cognate with German {{lang|de|Acker}}, Dutch {{lang|nl|akker}}, Latin {{lang|la|ager}}, Sanskrit {{lang|sa-Latn|ajr}}, and Greek {{lang|el|αγρός}} ({{lang|el-Latn|agros}}). In English, an obsolete variant spelling was aker. According to the Act on the Composition of Yards and Perches, dating from around 1300, an acre is "40 perches [rods] in length and four in breadth",{{cite book|author1=Great Britain|author2=Owen Ruffhead |author-link2=Owen Ruffhead |title=Statutes at Large |url=https://books.google.com/books?id=Un1RAAAAYAAJ&q=%22quod%20tria%20grana%22&pg=PA421 |access-date=12 February 2012 |year=1765 |publisher=Printed by M. Baskett |page=421| quote=It is ordained that 3 grains of barley dry and round do make an inch, 12 inches make 1 foot, 3 feet make 1 yard, 5 yards and a half make a perch, and 40 perches in length and 4 in breadth make an acre.}} meaning 220 yards by 22 yards.{{efn|22 yards is about 20 meters.}} As detailed in the diagram, an acre was roughly the amount of land tillable by a yoke of oxen in one day.{{cite encyclopedia |url=http://www.oed.com/viewdictionaryentry/Entry/1769|title=acre, n. |encyclopedia = Oxford English Dictionary | date = December 2011}}

Before the enactment of the metric system, many countries in Europe used their own official acres. In France, the traditional unit of area was the arpent carré, a measure based on the Roman system of land measurement.

The {{lang|fr|acre}} was used only in Normandy (and neighbouring places outside its traditional borders), but its value varied greatly across Normandy, ranging from 3,632 to 9,725 square metres, with 8,172 square metres being the most frequent value.{{clarify|date=June 2023|reason=What is this in traditional units? How was it measured?}} But inside the same {{lang|fr|pays}} of Normandy, for instance in pays de Caux, the farmers (still in the 20th century) made the difference between the {{lang|fr|grande acre}} (68 ares, 66 centiares) and the {{lang|fr|petite acre}} (56 to 65 ca).Raymond Mensire, {{lang|fr|Le Patois cauchois}}, 1939, p. 55. The Normandy {{lang|fr|acre}} was usually divided in 4 {{lang|fr|vergées}} (roods) and 160 square {{lang|fr|perches}}, like the English acre.

The Normandy {{lang|fr|acre}} was equal to 1.6 {{lang|fr|arpents}}, the unit of area more commonly used in Northern France outside of Normandy. In Canada, the Paris {{lang|fr|arpent}} used in Quebec before the metric system was adopted is sometimes called "French acre" in English, even though the Paris {{lang|fr|arpent}} and the Normandy {{lang|fr|acre}} were two very different units of area in ancient France (the Paris {{lang|fr|arpent}} became the unit of area of French Canada, whereas the Normandy {{lang|fr|acre}} was never used in French Canada).

In Germany, the Netherlands, and Eastern Europe the traditional unit of area was {{lang|de|Morgen}}. Like the acre, the morgen was a unit of ploughland, representing a strip that could be ploughed by one man and an ox or horse in a morning. There were many variants of the morgen, differing between the different German territories, ranging from {{convert|1/2|to|2+1/2|acre|m2}}. It was also used in Old Prussia, in the Balkans, Norway, and Denmark, where it was equal to about {{convert|2/3|acre|m2|spell=in}}. Statutory values for the acre were enacted in England, and subsequently the United Kingdom, by acts of:

• Edward I
• Edward III
• Henry VIII
• George IV
• Queen Victoria – the British Weights and Measures Act of 1878 defined it as containing 4,840 square yards.

Historically, the size of farms and landed estates in the United Kingdom was usually expressed in acres (or acres, roods, and perches), even if the number of acres was so large that it might conveniently have been expressed in square miles. For example, a certain landowner might have been said to own 32,000 acres of land, not 50 square miles of land.

The acre is related to the square mile, with 640 acres making up one square mile. One mile is 5280 feet (1760 yards). In western Canada and the western United States, divisions of land area were typically based on the square mile, and fractions thereof. If the square mile is divided into quarters, each quarter has a side length of {{frac|1|2}} mile (880 yards) and is {{frac|1|4}} square mile in area, or 160 acres. These subunits are typically then again divided into quarters, with each side being {{frac|1|4}} mile long, and being {{frac|1|16}} of a square mile in area, or 40 acres. In the United States, farmland was typically divided as such, and the phrase "the back 40" refers to the 40-acre parcel to the back of the farm. Most of the Canadian Prairie Provinces and the US Midwest are on square-mile grids for surveying purposes.

• Customary acre – The customary acre was roughly similar to the Imperial acre, but it was subject to considerable local variation similar to the variation in carucates, virgates, bovates, nooks, and farundels. These may have been multiples of the customary acre, rather than the statute acre.
• Builder's acre = an even {{convert|40000|sqft}} or {{convert|200|x|200|ft}}, used in US real-estate development to simplify the math and for marketing. It is nearly 10% smaller than a survey acre, and the discrepancy has led to lawsuits alleging misrepresentation.{{cite web |url=https://www.maxrealestateexposure.com/acre-land/ |title=How Much is an Acre of Land |website=Maximum Exposure Real Estate web site |access-date=6 August 2021}}
• Feddan - Middle Eastern measurement unit, {{convert|4200|m2|acre|sigfig=5}}.
• Scottish acre = 1.3 Imperial acres (5,080 m², an obsolete Scottish measurement)
• Irish acre = {{convert|7,840|yd2}}
• Cheshire acre = {{convert|10,240|yd2}}Holland, Robert. (1886). [https://archive.org/details/glossaryofwordsu16holluoft A glossary of words used in the County of Chester.] London: Trübner for the English Dialect Society. p. 3.
• Stremma or Greek acre ≈ 10,000 square Greek feet, but now set at exactly 1,000 square metres (a similar unit was the zeugarion){{cite book|last=Malcolm|first=Noel|title=Kosovo: A Short History|year=1999|publisher=Harper Perennial|isbn=978-0-06-097775-7}}
• Dunam or Turkish acre ≈ 1,600 square Turkish paces, but now set at exactly 1,000 square metres (a similar unit was the çift)
• Actus quadratus or Roman acre ≈ 14,400 square Roman feet (about 1,260 square metres)
• God's Acre – a synonym for a churchyard.{{Cite web|url=https://www.merriam-webster.com/dictionary/God%27s+acre|title=Definition of GOD'S ACRE|website=www.merriam-webster.com}}
• Long acre {{snd}} the grass strip on either side of a road that may be used for illicit grazing.
• Town acre was a term used in early 19th century in the planning of towns on a grid plan, such as Adelaide, South Australia{{cite web | title=Light's Plan of Adelaide, 1840 | website=Adelaidia|first=Jude|last=Elton|publisher=History Trust of South Australia | date=10 December 2013 | url=https://adelaidia.history.sa.gov.au/panoramas/lights-plan-of-adelaide-1840 | access-date=16 January 2021}}{{cite book|last=Llewellyn-Smith|first= Michael|chapter=The Background to the Founding of Adelaide and South Australia in 1836|title= Behind the Scenes: The Politics of Planning Adelaide|pages=11–38|publisher=University of Adelaide Press|date= 2012|jstor= 10.20851/j.ctt1sq5wvd.8|isbn= 9781922064400|access-date=16 January 2021|url=http://www.jstor.org/stable/10.20851/j.ctt1sq5wvd.8.}} and Wellington, New Plymouth and Nelson in New Zealand. The land was divided into plots of an Imperial acre, and these became known as town acres.{{cite web | website=Te Ara Encyclopedia of New Zealand | date= 26 March 2015|first=Ben |last=Schrader|title=City planning – Early settlement planning | url=https://teara.govt.nz/en/city-planning/page-1 | access-date=16 January 2021}}

{{Div col|colwidth=30em}}

• Acre-foot – used in US to measure a large water volume
• Anthropic units
• Arpent – used in Louisiana to measure length and area
• Conversion of units
• Jugerum – Roman unit of area
• Morgen ("morning") – normally {{frac|2|3}} of a Tagwerk ("day work") of ploughing with an ox
• Mu – Chinese acre
• Public Land Survey System
• Quarter acre
• Section (United States land surveying)
• Spanish units of measurement

{{div col end}}

{{notelist}}

{{Reflist}}

{{EB1911 poster|Acre (land measure)}}

• [https://web.archive.org/web/20101017003707/http://www.legislation.gov.uk/uksi/1995/1804/contents/made The Units of Measurement Regulations 1995 (United Kingdom)]

{{Imperial units}}

{{United States Customary Units}}

Category:Customary units of measurement in the United States

Category:Imperial units

Category:Surveying

Category:Units of area