Acre
acre | |
---|---|
US customary units, Imperial units | |
Unit of | area |
Symbol | ac, acre |
Conversions | |
1 ac in ... | ... is equal to ... |
SI units | = 4,046.8564224 m2 |
US customary, Imperial | ≡ 4,840 sq yd ≡ 1⁄640 sq mi |
The acre (/ˈeɪkər/ AY-kər) 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, 1⁄640 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[1] but is usually spelled out as the word "acre".[2]
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.[3]
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 used in many established and former
Description
One acre equals 1⁄640 (0.0015625) square mile, 4,840 square yards, 43,560 square feet,[2] or about 4,047 square metres (0.4047 hectares) (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;[4] 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 (63.61 metres), 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
Both the international acre and the US survey acre contain 1⁄640 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 (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.[6] Surveyors in the United States use both international and survey feet, and consequently, both varieties of acre.[7]
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.[8]
In October 2019, the
Spanish acre
The
Use
The acre is commonly used in many current and former Commonwealth countries by custom, and in a few it continues as a
Republic of Ireland
In the Republic of Ireland, the hectare is legally used under European units of measurement directives; however, the acre is still widely used, especially in agriculture. (This is the standard statute acre, the same as used in the UK, not the old Irish acre which was of a different size.)[34][35][36][37]
Indian subcontinent
In the
In Pakistan, residential plots are measured in kanal (20 marla = 1 kanal = 500 sq yards) and open/agriculture land measurement is in acres (8 kanal = 1 acre or 4 peli = 1 acre) and muraba (25 acres = 1 muraba = 200 kanal), jerib, wiswa and gunta.[citation needed]
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
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
- 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 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[47])
- 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 (1⁄10 of 880 yards by 1⁄16 of 880 yards), about 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 1.32 acres (0.53 ha).
For residents of other countries, the acre might be envisioned as rather more than half of a 1.76 acres (0.71 ha) football pitch.
Historical origin
The word acre is derived from Old English æcer originally meaning "open field", cognate with west coast Norwegian ækre, Icelandic akur, Swedish åker, German Acker, Dutch akker, Latin ager, Sanskrit ajr, and Greek αγρός (agros). In English, an obsolete variant spelling was aker.
According to the
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 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.[clarification needed] But inside the same pays of Normandy, for instance in pays de Caux, the farmers (still in the 20th century) made the difference between the grande acre (68 ares, 66 centiares) and the petite acre (56 to 65 ca).[50] The Normandy acre was usually divided in 4 vergées (roods) and 160 square perches, like the English acre.
The Normandy acre was equal to 1.6 arpents, the unit of area more commonly used in Northern France outside of Normandy. In Canada, the Paris arpent used in Quebec before the metric system was adopted is sometimes called "French acre" in English, even though the Paris arpent and the Normandy acre were two very different units of area in ancient France (the Paris arpent became the unit of area of French Canada, whereas the Normandy acre was never used in French Canada).
In Germany, the Netherlands, and Eastern Europe the traditional unit of area was , where it was equal to about two-thirds acre (2,700 m2).
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
- Weights and Measures Actof 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,
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 1⁄2 mile (880 yards) and is 1⁄4 square mile in area, or 160 acres. These subunits would typically then again be divided into quarters, with each side being 1⁄4 mile long, and being 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" would refer to the 40-acre parcel to the back of the farm. Most of the
Legacy units
- 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 40,000 square feet (3,700 m2) or 200 by 200 feet (61 m × 61 m), 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.[51]
- Scottish acre = 1.3 Imperial acres (5,080 m2, an obsolete Scottish measurement)
- Irish acre= 7,840 square yards (6,560 m2)
- Cheshire acre = 10,240 square yards (8,560 m2)[52]
- Dunam or Turkish acre ≈ 1,600 square Turkish paces, but now set at exactly 1,000 square metres (a similar unit was the çift)[53]
- Roman feet(about 1,260 square metres)
- God's Acre – a synonym for a churchyard.[54]
- Long acre – the grass strip on either side of a road that may be used for illicit grazing.
See also
- Acre-foot – used in US to measure a large water volume
- Anthropic units
- Conversion of units
- French arpent – used in Louisiana to measure length and area
- Jugerum
- a Morgen ("morning") of land is normally 2⁄3 of a Tagwerk ("day work") of ploughing with an ox
- Public Land Survey System
- Quarter acre
- Section (United States land surveying)
- Spanish customary units
Notes
- ^ 22 yards is about 20 meters.
References
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- ^ a b National Institute of Standards and Technology (n.d.) General Tables of Units of Measurement. Archived 26 November 2006 at the Wayback Machine.
- ^ "Manuscripts and Special Collections – Measurements". the University of Nottingham. Retrieved 1 August 2018.
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- ^ a b "Refinement of Values for the Yard and the Pound" (PDF). noaa.gov. National Bureau of Standards. 25 June 1959. Archived from the original (PDF) on 5 March 2020. Retrieved 3 December 2006.
- PMID 17833047. Retrieved 16 August 2021.
- National Geodetic Survey, (January 1991), Policy of the National Geodetic Survey Concerning Units of Measure for the State Plane Coordinate System of 1983.
- ^ 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.]
- ^ "NGS and NIST to Retire U.S. Survey Foot after 2022". National Geodetic Survey. 31 October 2019. Retrieved 4 March 2020.
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- ^ Waddesdon Estate: about us "By purchasing the adjoining land, the estate has grown from the original 2,700 acres in 1874 to 6,000 acres in 2011. " Waddesdon Manor Estate
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- perch, and 40 perches in length and 4 in breadth make an acre.
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