Acre

Template:Short description Template:About Template:Redirect Template:Use dmy dates Template:Use British English Template:Infobox unit

File:Comparison of units of area.png

Image comparing the acre (the small pink area at lower left) to other units. The entire yellow square is one square mile; the dark blue area at right represents 100 acres.

The acre (Template:IPAc-en Template:Respell) is a unit of land area used in the British imperial and the United States customary systems. It is traditionally defined as the area of one chain by one furlong (66 by 660 feet), which is exactly equal to 10 square chains, Template:Frac of a square mile, 4,840 square yards, or 43,560 square feet, and approximately 4,047 m², or about 40% of a hectare. Based upon the international yard and pound agreement of 1959, an acre may be declared as exactly 4,046.8564224 square metres. The acre is sometimes abbreviated ac,<ref>Template:Cite book</ref> but is usually spelled out as the word "acre".<ref name="NIST">National Institute of Standards and Technology (n.d.) General Tables of Units of Measurement. Template:Webarchive.</ref>

Traditionally, in the Middle Ages, an acre was conceived of as the area of land that could be ploughed by one man using a team of eight oxen in one day.<ref name=nottingham>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The acre is still a statutory measure in the United States. Both the international acre and the US survey acre are in use, but they differ by only four parts per million. The most common use of the acre is to measure tracts of land. The acre is used in many established and former Commonwealth of Nations countries by custom. In a few, it continues as a statute measure, although not since 2010 in the UK, and not for decades in Australia, New Zealand, and South Africa. In many places where it is not a statute measure, it is still lawful to "use for trade" if given as supplementary information and is not used for land registration.

DescriptionEdit

One acre equals Template:Frac (0.0015625) square mile, 4,840 square yards, 43,560 square feet,<ref name="NIST" /> or about Template:Convert (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;<ref name="Klein2012">Template:Cite book</ref> 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 (Template:Convert), on a side. As a unit of measure, an acre has no prescribed shape; any area of 43,560 square feet is an acre.

US survey acresEdit

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.<ref name=NBS1959>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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]'.<ref name=NBS1959 /> By inference, an "international acre" may be calculated as exactly Template:Gaps square metres but it does not have a basis in any international agreement.

Both the international acre and the US survey acre contain Template:Frac 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 (Template:Sfrac m²) is based on an inch defined by 1 metre = 39.37 inches exactly, as established by the Mendenhall Order of 1893.<ref>* Template:Cite journal</ref> Surveyors in the United States use both international and survey feet, and consequently, both varieties of acre.<ref>National Geodetic Survey, (January 1991), Policy of the National Geodetic Survey Concerning Units of Measure for the State Plane Coordinate System of 1983.</ref>

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.<ref>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.]</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Spanish acreEdit

The Puerto Rican cuerda (Template:Convert) is sometimes called the "Spanish acre" in the continental United States.<ref name="Rowlett">Units: C: cuerda. Russ Rowlett. The University of North Carolina at Chapel Hill.</ref>

UseEdit

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,<ref name="antiguaobserver">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> American Samoa,<ref name="samoanews">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The Bahamas,<ref name="thenassauguardian">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Belize,<ref name="amandala">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> the British Virgin Islands,<ref name="bvibeacon">{{#invoke:citation/CS1|citation |CitationClass=web }},</ref> Canada,<ref name="Statistics Canada">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> the Cayman Islands,<ref name="compasscayman">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Dominica,<ref name="dominicanewsonline">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> the Falkland Islands,<ref name="penguin-news">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Grenada,<ref name="grenadabroadcast">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Ghana,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Guam,<ref name="guampdn">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> the Northern Mariana Islands,<ref name="saipantribune">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Jamaica,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Montserrat,<ref name="themontserratreporter">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Samoa,<ref name="samoaobserver">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Saint Lucia,<ref name="thevoiceslu">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> St. Helena,<ref name="sthelenaonline">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> St. Kitts and Nevis,<ref name="thestkittsnevisobserver">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> St. Vincent and the Grenadines,<ref name="iwnsvg">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Turks and Caicos,<ref name="suntci">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> the United Kingdom, the United States, and the US Virgin Islands.<ref name="virginislandsdailynews">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Republic of IrelandEdit

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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Indian subcontinentEdit

In India, residential plots are measured in square feet or square metre, while agricultural land is measured in acres.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In Sri Lanka, the division of an acre into 160 perches or 4 roods is common.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In Pakistan, residential plots are measured in {{#invoke:Lang|lang}} (20 {{#invoke:Lang|lang}} = 1 {{#invoke:Lang|lang}} = 605 sq yards) and open/agriculture land measurement is in acres (8 {{#invoke:Lang|lang}} = 1 acre) and {{#invoke:Lang|lang}} (25 acres = 1 {{#invoke:Lang|lang}} = 200 {{#invoke:Lang|lang}}), {{#invoke:Lang|lang}} and {{#invoke:Lang|lang}}.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

United KingdomEdit

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,<ref name= UK1994>The Weights and Measures Act 1985 (Metrication) (Amendment) Order 1994 HM Government, 1995</ref> where it was replaced by the hectare Template:Snd though its use as a supplementary unit continues to be permitted indefinitely.<ref name="legislation_20093045">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This was with the exemption of land registration,<ref name= UK1994 /> which records the sale and possession of land;<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> in 2010 HM Land Registry ended its exemption.<ref name="legislation_20093045"/> The measure is still used to communicate with the public,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and informally (non-contract) by the farming and property industries.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite news</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Equivalence to other units of areaEdit

File:Acre superimposed over football fields.svg

The area of one acre (red) superposed on an American football 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<ref>Template:Cite journal</ref>)
Template:Frac (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 (Template:Frac of 880 yards by Template:Frac of 880 yards), about Template:Frac 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 Template:Convert. For residents of other countries, the acre might be envisioned as rather more than half of a Template:Convert football pitch.

Historical originEdit

Template: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».<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Acre dates back to the old Scandinavian akr “cultivated field, ploughed land” which is perpetuated in Icelandic and the Faroese {{#invoke:Lang|lang}} “field (wheat)”, Norwegian and Swedish {{#invoke:Lang|lang}}, Danish {{#invoke:Lang|lang}} “field”, cognate with German {{#invoke:Lang|lang}}, Dutch {{#invoke:Lang|lang}}, Latin {{#invoke:Lang|lang}}, Sanskrit {{#invoke:Lang|lang}}, and Greek {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}). 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",<ref name="BritainRuffhead1765">Template:Cite book</ref> meaning 220 yards by 22 yards.Template:Efn As detailed in the diagram, an acre was roughly the amount of land tillable by a yoke of oxen in one day.<ref>Template:Cite encyclopedia</ref>

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 {{#invoke:Lang|lang}} 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.Template:Clarify But inside the same {{#invoke:Lang|lang}} of Normandy, for instance in pays de Caux, the farmers (still in the 20th century) made the difference between the {{#invoke:Lang|lang}} (68 ares, 66 centiares) and the {{#invoke:Lang|lang}} (56 to 65 ca).<ref>Raymond Mensire, {{#invoke:Lang|lang}}, 1939, p. 55.</ref> The Normandy {{#invoke:Lang|lang}} was usually divided in 4 {{#invoke:Lang|lang}} (roods) and 160 square {{#invoke:Lang|lang}}, like the English acre.

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

In Germany, the Netherlands, and Eastern Europe the traditional unit of area was {{#invoke:Lang|lang}}. 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 Template:Convert. It was also used in Old Prussia, in the Balkans, Norway, and Denmark, where it was equal to about Template:Convert. 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 Template:Frac mile (880 yards) and is Template:Frac square mile in area, or 160 acres. These subunits are typically then again divided into quarters, with each side being Template:Frac mile long, and being Template:Frac 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.

Legacy unitsEdit

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 Template:Convert or Template:Convert, 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.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

Feddan - Middle Eastern measurement unit, Template:Convert.
Scottish acre = 1.3 Imperial acres (5,080 m², an obsolete Scottish measurement)
Irish acre = Template:Convert
Cheshire acre = Template:Convert<ref>Holland, Robert. (1886). A glossary of words used in the County of Chester. London: Trübner for the English Dialect Society. p. 3.</ref>
Stremma or Greek acre ≈ 10,000 square Greek feet, but now set at exactly 1,000 square metres (a similar unit was the zeugarion)<ref name=Malcolm>Template:Cite book</ref>
Dunam or Turkish acre ≈ 1,600 square Turkish paces, but now set at exactly 1,000 square metres (a similar unit was the çift)<ref name=Malcolm/>
Actus quadratus or Roman acre ≈ 14,400 square Roman feet (about 1,260 square metres)
God's Acre – a synonym for a churchyard.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

Long acre Template: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<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref><ref>Template:Cite book</ref> 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.<ref name=encycnz>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>