Acre

Based upon the international yard and pound agreement of 1959, an acre may be declared as exactly 4,046.8564224 square metres.

[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.

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.

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.

Areas are seldom measured with sufficient accuracy for the different definitions to be detectable.

[8] 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.

[11] The acre is commonly used in many current and former Commonwealth countries by custom, and in a few it continues as a statute measure.

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».

[a] As detailed in the diagram, an acre was roughly the amount of land tillable by a yoke of oxen in one day.

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.

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 area of one acre (red) superposed on an American football field (green) and Association football /soccer pitch (blue)
Farm-derived units of measurement:
  1. The rod is a historical unit of length equal to 5 + 1 ⁄ 2 yards. It may have originated from the typical length of a mediaeval ox-goad . There are 4 rods in one chain .
  2. The furlong (meaning furrow length) was the distance a team of oxen could plough without resting. This was standardised to be exactly 40 rods or 10 chains.
  3. An acre was the amount of land tillable by one man behind one team of eight oxen in one day. Traditional acres were long and narrow due to the difficulty in turning the plough and the value of river front access .
  4. An oxgang was the amount of land tillable by one ox in a ploughing season. This could vary from village to village, but was typically around 15 acres.
  5. A virgate was the amount of land tillable by two oxen in a ploughing season.
  6. A carucate was the amount of land tillable by a team of eight oxen in a ploughing season. This was equal to 8 oxgangs or 4 virgates.