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The acre is a
unit Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action, a discrete piece of action (or beat) in a theatrical presentation Music * ''Unit'' (a ...
of land area used in the imperial and US customary systems. It is traditionally defined as the area of one chain by one
furlong A furlong is a measure of distance in imperial units and United States customary units equal to one eighth of a mile, equivalent to 660 feet, 220 yards, 40 rods, 10 chains or approximately 201 metres. It is now mostly confined to use in hor ...
(66 by 660 feet), which is exactly equal to 10 square chains, of a square mile, 4,840 square yards, or 43,560 square feet, and approximately 4,047 m2, or about 40% of a
hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100- metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is ...
. 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 but is usually spelled out as the word "acre".National Institute of Standards and Technolog
(n.d.) General Tables of Units of Measurement
.
Traditionally, in the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...
, an acre was conceived of as the area of land that could be ploughed by one man using a team of 8 oxen in one day. 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 (see below). The most common use of the acre is to measure tracts of land. The acre is commonly used in a number of current and former
British Commonwealth The Commonwealth of Nations, simply referred to as the Commonwealth, is a political association of 56 member states, the vast majority of which are former territories of the British Empire. The chief institutions of the organisation are the Co ...
countries by custom only. In a few, it continues as a
statute measure Weights and measures acts are acts of the British Parliament determining the regulation of weights and measures. It also refers to similar royal and parliamentary acts of the Kingdoms of England and Scotland and the medieval Welsh states. T ...
, although since 2010 not in the UK itself, and not since decades ago in Australia,
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
and
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
. In many of those 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.


Description

One acre equals (0.0015625) square mile, 4,840 square yards, 43,560 square feet, or about (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 selion of land sized at forty perches (660 ft, or 1 
furlong A furlong is a measure of distance in imperial units and United States customary units equal to one eighth of a mile, equivalent to 660 feet, 220 yards, 40 rods, 10 chains or approximately 201 metres. It is now mostly confined to use in hor ...
) long and four perches (66 ft) wide; 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 In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90- degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length a ...
enclosing one acre is approximately 69.57 yards, or 208 feet 9 inches (), 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 acres

In the
international yard and pound The international yard and pound are two units of measurement that were the subject of an agreement among representatives of six nations signed on 1 July 1959: the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. T ...
agreement of 1959, the United States and five countries of the
Commonwealth of Nations The Commonwealth of Nations, simply referred to as the Commonwealth, is a political association of 56 member states, the vast majority of which are former territories of the British Empire. The chief institutions of the organisation are the ...
defined the international yard to be exactly 0.9144 metre. The US authorities decided that, while the refined definition would apply nationally in all other respects, the
US survey foot The foot ( feet), standard symbol: ft, is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, , is a customarily used alternative symbol. Since the International Yard and P ...
(and thus the survey acre) would continue 'until such a time as it becomes desirable and expedient to readjust t. By inference, an "international acre" may be calculated as exactly square metres but it does not have a basis in any international agreement. Both the international acre and the US survey acre contain of a square mile or 4,840 square yards, but alternative definitions of a yard are used (see
survey foot The foot ( feet), standard symbol: ft, is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, , is a customarily used alternative symbol. Since the International Yard and P ...
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 ( m2) is based on an inch defined by 1 metre = 39.37 inches exactly, as established by the
Mendenhall Order The Mendenhall Order marked a decision to change the fundamental standards of length and mass of the United States from the customary standards based on those of England to metric standards. It was issued on April 5, 1893, by Thomas Corwin Mend ...
of 1893. Surveyors in the United States use both international and survey feet, and consequently, both varieties of acre. 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 Letter or ANSI Letter is a paper size standard defined by the American National Standards Institute, commonly used as home or office stationery in the United States, Canada, Chile, Colombia, Costa Rica, Mexico, Panama, Guatemala, the Dominican ...
, it is usually not important which one is being discussed. Areas are seldom measured with sufficient accuracy for the different definitions to be detectable. In October 2019,
US National Geodetic Survey The National Geodetic Survey (NGS) is a United States federal agency that defines and manages a national coordinate system, providing the foundation for transportation and communication; mapping and charting; and a large number of applications ...
and
National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...
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.


Spanish acre

The
Puerto Rica Puerto, a Spanish word meaning ''seaport'', may refer to: Places *El Puerto de Santa María, Andalusia, Spain *Puerto, a seaport town in Cagayan de Oro City, Philippines *Puerto Colombia, Colombia *Puerto Cumarebo, Venezuela *Puerto Galera, Orient ...
n '' cuerda'' () is sometimes called the "Spanish acre" in the continental United States.''Units: C: cuerda''
Russ Rowlett. The University of North Carolina at Chapel Hill.


Use

The acre is commonly used in a number of current and former Commonwealth countries by custom, and in a few it continues as a
statute measure Weights and measures acts are acts of the British Parliament determining the regulation of weights and measures. It also refers to similar royal and parliamentary acts of the Kingdoms of England and Scotland and the medieval Welsh states. T ...
. These include Antigua and Barbuda,
American Samoa American Samoa ( sm, Amerika Sāmoa, ; also ' or ') is an unincorporated territory of the United States located in the South Pacific Ocean, southeast of the island country of Samoa. Its location is centered on . It is east of the Internationa ...
,
The Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the ar ...
, Belize, the
British Virgin Islands ) , anthem = "God Save the King" , song_type = Territorial song , song = " Oh, Beautiful Virgin Islands" , image_map = File:British Virgin Islands on the globe (Americas centered).svg , map_caption = , mapsize = 290px , image_map2 = Bri ...
, the Cayman Islands, Dominica, the
Falkland Islands The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubouze ...
, Grenada,
Ghana Ghana (; tw, Gaana, ee, Gana), officially the Republic of Ghana, is a country in West Africa. It abuts the Gulf of Guinea and the Atlantic Ocean to the south, sharing borders with Ivory Coast in the west, Burkina Faso in the north, and To ...
,
Guam Guam (; ch, Guåhan ) is an organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. It is the westernmost point and territory of the United States (reckoned from the geographic cent ...
, the
Northern Mariana Islands The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI; ch, Sankattan Siha Na Islas Mariånas; cal, Commonwealth Téél Falúw kka Efáng llól Marianas), is an unincorporated territory and commonw ...
,
Jamaica Jamaica (; ) is an island country situated in the Caribbean Sea. Spanning in area, it is the third-largest island of the Greater Antilles and the Caribbean (after Cuba and Hispaniola). Jamaica lies about south of Cuba, and west of His ...
, Montserrat,
Samoa Samoa, officially the Independent State of Samoa; sm, Sāmoa, and until 1997 known as Western Samoa, is a Polynesian island country consisting of two main islands ( Savai'i and Upolu); two smaller, inhabited islands ( Manono and Apolima); ...
, Saint Lucia, St. Helena, St. Kitts and Nevis, St. Vincent and the Grenadines,
Turks and Caicos The Turks and Caicos Islands (abbreviated TCI; and ) are a British Overseas Territory consisting of the larger Caicos Islands and smaller Turks Islands, two groups of tropical islands in the Lucayan Archipelago of the Atlantic Ocean and n ...
, the United Kingdom, the United States and the
US Virgin Islands The United States Virgin Islands,. Also called the ''American Virgin Islands'' and the ''U.S. Virgin Islands''. officially the Virgin Islands of the United States, are a group of Caribbean islands and an unincorporated and organized territory ...
.


South Asia

In India, residential plots are measured in square feet, while agricultural land is measured in acres. In Sri Lanka, the division of an acre into 160  perches or 4  roods is common. In Pakistan, residential plots is measured in (20 = 1 = 500 sq yards) and open/agriculture land measurement is in acres (8 = 1 acre or 4 = 1 acre) and (25 acres = 1 = 200 ), and .


United Kingdom

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,The Weights and Measures Act 1985 (Metrication) (Amendment) Order 1994
HM Government, 1995
where it was replaced by the
hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100- metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is ...
though its use as a supplementary unit continues to be permitted indefinitely. This was with exemption of Land registration, which records the sale and possession of land, in 2010 HM Land Registry ended its exemption. The measure is still used to communicate with the public, and informally (non-contract) by the farming and property industries.


Equivalence to other units of area

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 The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100- metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is ...
*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) * (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 ( of 880 yards by of 880 yards), about the size of a standard
American football field The rectangular field of play used for American football games measures long between the goal lines, and (53.3 yards) wide. The field may be made of grass or artificial turf. In addition, there are end zones extending another past the goal li ...
. 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 end zone is the scoring area on the field, according to gridiron-based codes of football. It is the area between the end line and goal line bounded by the sidelines. There are two end zones, each being on an opposite side of the field. ...
). The full field, including the end zones, covers about . For residents of other countries, the acre might be envisioned as rather more than half of a
football pitch A football pitch (also known as soccer field) is the playing surface for the game of association football. Its dimensions and markings are defined by Law 1 of the Laws of the Game, "The Field of Play". The pitch is typically made of natural t ...
. It may also be remembered as 1% short of 44,000 square feet.


Historical origin

The word ''acre'' is derived from
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlers in the mid-5th c ...
originally meaning "open field", cognate with west coast Norwegian , Icelandic ,
Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used by ...
, German ,
Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...
,
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
,
Sanskrit Sanskrit (; attributively , ; nominally , , ) is a classical language belonging to the Indo-Aryan branch of the Indo-European languages. It arose in South Asia after its predecessor languages had diffused there from the northwest in the late ...
, and Greek (). 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
perch Perch is a common name for fish of the genus ''Perca'', freshwater gamefish belonging to the family Percidae. The perch, of which three species occur in different geographical areas, lend their name to a large order of vertebrates: the Per ...
es rods.html" ;"title="rod_(unit).html" ;"title="/nowiki>rod (unit)">rods">rod_(unit).html" ;"title="/nowiki>rod (unit)">rodsin length and four in breadth", meaning 220 yards by 22 yards. As detailed in the box on the right, an acre was roughly the amount of land tillable by a yoke of oxen in one day. Before the enactment of the metric system, many countries in Europe used their own official acres. In France, the 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. But inside the same of Normandy, for instance in
pays de Caux The Pays de Caux (, , literally ''Land of Caux'') is an area in Normandy occupying the greater part of the French ''département'' of Seine Maritime in Normandy. It is a chalk plateau to the north of the Seine Estuary and extending to the cliffs o ...
, the farmers (still in the 20th century) made the difference between the (68 ares, 66 centiares) and the (56 to 65 ca). The Normandy was usually divided in 4 ( roods) and 160 square , like the English acre. The Normandy was equal to 1.6 , the unit of area more commonly used in Northern France outside of Normandy. In Canada, the Paris used in
Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...
before the metric system was adopted is sometimes called "French acre" in English, even though the Paris and the Normandy were two very different units of area in ancient France (the Paris became the unit of area of French Canada, whereas the Normandy was never used in French Canada). The German word for acre is . There were many variants of the , differing between the different German territories: 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 George IV (George Augustus Frederick; 12 August 1762 – 26 June 1830) was King of the United Kingdom of Great Britain and Ireland and King of Hanover from the death of his father, King George III, on 29 January 1820, until his own death ten y ...
*
Queen Victoria Victoria (Alexandrina Victoria; 24 May 1819 – 22 January 1901) was Queen of the United Kingdom of Great Britain and Ireland from 20 June 1837 until her death in 1901. Her reign of 63 years and 216 days was longer than that of any previo ...
– 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,
rood A rood or rood cross, sometimes known as a triumphal cross, is a cross or crucifix, especially the large crucifix set above the entrance to the chancel of a medieval church. Alternatively, it is a large sculpture or painting of the crucifixion ...
s, 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 mile (880 yards) and is square mile in area, or 160 acres. These subunits would typically then again be divided into quarters, with each side being mile long, and being 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" would refer 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 acres

* 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
carucate The carucate or carrucate ( lat-med, carrūcāta or ) was a medieval unit of land area approximating the land a plough team of eight oxen could till in a single annual season. It was known by different regional names and fell under different forms ...
s,
virgate The virgate, yardland, or yard of land ( la, virgāta was an English unit of land. Primarily a measure of tax assessment rather than area, the virgate was usually (but not always) reckoned as   hide and notionally (but seldom exactly) equa ...
s, bovates, nooks, and farundels. These may have been multiples of the customary acre, rather than the statute acre. * Builder's acre = an even or , 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. * Scottish acre = 1.3 Imperial acres (5,080 m2, an obsolete Scottish measurement) * Irish acre = * Cheshire acre = *
Stremma The stremma ( stremmata; el, στρέμμα, ''strémma'') is a Greek unit of land area equal to 1,000 square metres. Historically, stremmata were not standardized, and may have been anywhere from . History The ancient Greek equivalent was the s ...
or Greek acre ≈ 10,000 square Greek feet, but now set at exactly 1,000 square metres (a similar unit was the zeugarion) * 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 The ancient Roman units of measurement were primarily founded on the Hellenic system, which in turn was influenced by the Egyptian system and the Mesopotamian system. The Roman units were comparatively consistent and well documented. Length ...
(about 1,260 square metres) * God's Acre – a synonym for a churchyard. *
Long acre Long Acre is a street in the City of Westminster in central London. It runs from St Martin's Lane, at its western end, to Drury Lane in the east. The street was completed in the early 17th century and was once known for its coach-makers, and la ...
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 Adelaide ( ) is the capital city of South Australia, the state's largest city and the fifth-most populous city in Australia. "Adelaide" may refer to either Greater Adelaide (including the Adelaide Hills) or the Adelaide city centre. The dem ...
,
South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...
and
Wellington Wellington ( mi, Te Whanganui-a-Tara or ) is the capital city of New Zealand. It is located at the south-western tip of the North Island, between Cook Strait and the Remutaka Range. Wellington is the second-largest city in New Zealand by metr ...
, New Plymouth and
Nelson Nelson may refer to: Arts and entertainment * ''Nelson'' (1918 film), a historical film directed by Maurice Elvey * ''Nelson'' (1926 film), a historical film directed by Walter Summers * ''Nelson'' (opera), an opera by Lennox Berkeley to a lib ...
in New Zealand. The land was divided into plots of an Imperial acre, and these became known as town acres.


See also

*
Acre-foot The acre-foot is a non- SI unit of volume equal to about commonly used in the United States in reference to large-scale water resources, such as reservoirs, aqueducts, canals, sewer flow capacity, irrigation water, and river flows. An acre-f ...
– used in US to measure a large water volume *
Anthropic units The term anthropic unit (from Greek '' άνθρωπος'' meaning human) is used with different meanings in archaeology, in measurement and in social studies. In archaeology In archaeology, ''anthropic units'' are strata, or deposits of materi ...
*
Conversion of units Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors which change the measured quantity value without changing its effects. Overview The process ...
* French arpent – used in
Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...
to measure length and area *
Jugerum The jugerum or juger ( la, iūgerum, ', ', or ') was a Roman unit of area, equivalent to a rectangle 240 Roman feet in length and 120 feet in width (about 71×35½m), i.e. 28,800 square Roman feet ( la, pedes quadratum) or about hectare (0.62 ...
* a Morgen ("morning") of land is normally of a Tagwerk ("day work") of ploughing with an ox *
Public Land Survey System The Public Land Survey System (PLSS) is the surveying method developed and used in the United States to plat, or divide, real property for sale and settling. Also known as the Rectangular Survey System, it was created by the Land Ordinance of 178 ...
* Quarter acre * Section (United States land surveying) * Spanish customary units


Notes


References


External links


The Units of Measurement Regulations 1995 (United Kingdom)
{{United States Customary Units Customary units of measurement in the United States Imperial units Surveying Units of area