|Unit system||US customary units, Imperial units|
|Symbol||ac or acre|
|1 ac in ...||... is equal to ...|
|SI units||≈ 4,046.9 m2|
|US customary, Imperial|| ≡ 4,840 sq yd|
≡ 1⁄640 sq mi
The acre is a unit of land area used in the imperial and US 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 but is usually spelled out as the word "acre".
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 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 countries by custom only. In a few, it continues as a statute measure, although since 2010 not in the UK itself, and not since decades ago in Australia, New Zealand and South Africa. 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.
One acre equals 1⁄640 (0.0015625) square mile, 4,840 square yards, 43,560 square feet, 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 selion of land sized at forty perches (660 ft, or 1 furlong) 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 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.
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. 4,046.8564224 square metres but it does not have a basis in any international agreement.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
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. 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, 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 and 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.
The Puerto Rican cuerda (0.39 ha; 0.97 acres) is sometimes called the "Spanish acre" in the continental United States.
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. These include Antigua and Barbuda,American Samoa, The Bahamas, Belize, the British Virgin Islands, the Cayman Islands, Dominica, the Falkland Islands, Grenada, Ghana, Guam, the Northern Mariana Islands, Jamaica, Montserrat, Samoa, Saint Lucia, St. Helena, St. Kitts and Nevis, St. Vincent and the Grenadines, Turks and Caicos, the United Kingdom, the United States and the US Virgin Islands.
In India, residential plots are measured in square feet, while agricultural land is measured in acres. perches or 4 roods is common.In Sri Lanka, the division of an acre into 160
In Pakistan, residential plots is 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 ]
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, – 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.where it was replaced by the hectare
1 international acre is equal to the following metric units:
1 United States survey acre is equal to:
1 acre (both variants) is equal to the following customary units:
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.
It may also be remembered as 1% short of 44,000 square feet.
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 Act on the Composition of Yards and Perches, dating from around 1300, an acre is "40 perches [ rods] in 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 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. 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). 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).
The German word for acre is Morgen . There were many variants of the Morgen, differing between the different German territories:
|Place||Name||Area in m2||Area in (local)|
|Prussia (1816–1869)||Magdeburg Morgen||2,553.22||180|
|Saxony (1781)||Morgen, Scheffel (Aussaat)||2,767||150|
|Grand Duchy of Baden (from 1810)||Badischer Morgen||3,600||400|
|Württemberg (1806–1871)||Schwäbischer Morgen||3,152||384|
|Bergisches Land||Bergischer Morgen||2,132||120|
|Cologne, Rhineland||Rheinländischer Morgen||3,176||150|
|Hanover (before 1836)||2,608||120|
|Hanover (from 1836)||2,621||120|
|Holstein||Tonne (Tønde)||5,046||240 QGeestR|
|Frankfurt am Main||Feldmorgen||2,025||160 QFeldR|
|Frankfurt am Main||Waldmorgen||3,256||160 QWaldR|
|Altes Land (Harburg und Stade)||8,185|
Statutory values for the acre were enacted in England, and subsequently the United Kingdom, by acts of:
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 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 Canadian Prairie Provinces and the US Midwest are on square-mile grids for surveying purposes.
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 horse racing, where in many countries it is the standard measurement of race lengths, and agriculture, where is it used to measure rural field lengths and distances.
The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older English unit of length equal to 5,280 English feet, or 1,760 yards. The statute mile was standardised between the British Commonwealth and the United States by an international agreement in 1959, when it was formally redefined with respect to SI units as exactly 1,609.344 metres.
The yard is an English unit of length in both the British imperial and US customary systems of measurement equalling 3 feet or 36 inches. Since 1959 it has been by international agreement standardized as exactly 0.9144 meter. A distance of 1,760 yards is equal to 1 mile.
The square mile is an imperial and US unit of measure for area. One square mile is an area equal to the area of a square with sides of length one mile.
A fathom is a unit of length in the imperial and the U.S. customary systems equal to 6 feet (1.8288 m), used especially for measuring the depth of water. The fathom is neither an International Standard (SI) unit, nor an internationally-accepted non-SI unit. Historically, however, it is the most frequently employed maritime measure of depth in the English-speaking world.
A unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. In the United States the U.S. customary units are also in use. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units.
The rod, perch, or pole is a surveyor's tool and unit of length of various historical definitions, often between approximately 3 and 8 meters. In modern US customary units it is defined as 16+1⁄2 US survey feet, equal to exactly 1⁄320 of a mile, or a quarter of a surveyor's chain, and is exactly 5.0292 meters. The rod is useful as a unit of length because integer multiples of it can form one acre of square measure (area). The 'perfect acre' is a rectangular area of 43,560 square feet, bounded by sides 660 feet long and 66 feet wide or, equivalently, 40 rods and 4 rods. An acre is therefore 160 square rods or 10 square chains.
The chain is a unit of length equal to 66 feet, used in both the US customary and Imperial unit systems. It is subdivided into 100 links or 4 rods. There are 10 chains in a furlong, and 80 chains in one statute mile. In metric terms, it is 20.1168 m long. By extension, chainage is the distance along a curved or straight survey line from a fixed commencing point, as given by an odometer.
The following systems arose from earlier systems, and in many cases utilise parts of much older systems. For the most part they were used to varying degrees in the Middle Ages and surrounding time periods. Some of these systems found their way into later systems, such as the Imperial system and even SI.
Gunter's chain is a distance measuring device used for surveying. It was designed and introduced in 1620 by English clergyman and mathematician Edmund Gunter (1581–1626). It enabled plots of land to be accurately surveyed and plotted, for legal and commercial purposes.
The link, sometimes called a Gunter’s link, is a unit of length formerly used in many English-speaking countries. In US customary units modern definition, the link is exactly 66⁄100 of a US survey foot, or exactly 7.92 inches or approximately 20.12 cm.
An arpent is a unit of length and a unit of area. It is a pre-metric French unit based on the Roman actus. It is used in Quebec, some areas of the United States that were part of French Louisiana, and in Mauritius and the Seychelles.
English units are the units of measurement used in England up to 1826, which evolved as a combination of the Anglo-Saxon and Roman systems of units. Various standards have applied to English units at different times, in different places, and for different applications.
A vergée is a unit of land area, a quarter of the old French arpent. The term derives from Latin virga (rod). Compare French verge (yard).
The bigha is a traditional unit of measurement of area of a land, commonly used in northern India, Bangladesh and Nepal. There is no "standard" size of bigha. The size of a bigha varies considerably from place to place.
There are a number of Spanish units of measurement of length or area that are virtually obsolete due to metrication. They include the vara, the cordel, the league and the labor. The units of area used to express the area of land are still encountered in some transactions in land today.
A rood is a historic English and international inch-pound measure of area, as well as an archaic English measure of length.
The imperial and US customary measurement systems are both derived from an earlier English system of measurement which in turn can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure.
The History of measurement systems in Pakistan begins in early Indus Valley civilization when pastoral societies used barter to exchange goods or services and needed units of measurement.
Irish measure or plantation measure was a system of units of land measurement used in Ireland from the 16th century plantations until the 19th century, with residual use into the 20th century. The units were based on "English measure" but used a linear perch measuring 7 yards (6.4 m) as opposed to the English rod of 5.5 yards (5.0 m). Thus, linear units such as the furlong and mile, which were defined in terms of perches, were longer by a factor of 14:11 in Irish measure, while units of area, such as the rood or acre, were larger by 196:121. The Weights and Measures Act 1824 mandated the use throughout the British Empire of "Imperial measure", also called "statute measure", based on English measure. Imperial measure soon replaced Irish measure in the use of the Dublin Castle administration, but Irish measure persisted in local government, and longer still in private use.
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.