Image comparing the hectare (the small blue area at lower left) to other units. The entire yellow square is one square mile.
The hectare (/ˈhɛktɛər,-tɑːr/; SI symbol: ha) is a non-SImetric unit of area equal to a square with 100-metre sides, that is, 10,000 square metres (10,000 m2), and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is about 0.405 hectares and thus one hectare is about 2.47 acres.
St. Enda's GAA ground, in Omagh. The playing field used in Gaelic football and hurling is a little over a hectare in size.
In 1795, when the metric system was introduced, the are was defined as 100 square metres, or one square decametre, and the hectare ("hecto-" + "are") was thus 100 ares. When the metric system was further rationalised in 1960, resulting in the International System of Units (SI), the are was not included as a recognised unit, and from 2026 the hectare is no longer described by the International Bureau of Weights and Measures (BIPM) as accepted for use with the SI.[1]
The name was coined in French, from the Latin ārea.[3] The hectare is equivalent to 10,000 square metres. It is widely used throughout the world for the measurement of large areas of land,[4] and it is the legal unit of measure in some domains concerned with land ownership, planning, and management, including law (land deeds), agriculture, forestry, and town planning throughout the European Union,[5]South Africa, New Zealand, Australia, Canada and the United Kingdom.
However, the United States and Myanmar (Burma)[6][7] use the acre instead of the hectare for measuring surface or land area.
In many countries, metrification redefined or clarified existing measures in terms of metric units. The following legacy units of area have been redefined as being equal to one hectare:[8]
In Mexico, land area measurements are commonly given as combinations of hectares, ares, and centiares.[12] These are commonly written separated by a hyphen; for example, 1-21-00.26 ha would mean 1 hectare, 21 are, and 0.26 centiare (12100.26m2).
History
The metric system of measurement was first given a legal basis in 1795 by the French Revolutionary government. The law of 18 Germinal, Year III (7 April 1795) defined five units of measure:[13]
In 1972, the European Economic Community (EEC) passed directive 71/354/EEC,[16] which catalogued the units of measure that might be used within the Community. The units that were catalogued replicated the recommendations of the CGPM, supplemented by a few other units including the are (and implicitly the hectare) whose use was limited to the measurement of land.
Unit family
Definition of a hectare and of an are
The names centiare, deciare, decare and hectare are derived by adding the standard metric prefixes to the original base unit of area, the are.
Decimilliare
The decimilliare (dma, sometimes seen in cadastre area evaluation of real estate plots) is 1/10,000 are or one square decimetre.[17] Such usage of a double prefix is non-standard. The decimilliare is (100mm)2 or roughly a four-inch-by-four-inch square. (The decimilliare is smaller by approximately 3.1%.)
The deciare (rarely used) is ten square metres.[20]
Are
The are (/ɛər/,/ɛr/[21][22]) is a unit of area, equal to 100 square metres (10m × 10m), used for measuring land area. It was defined by older forms of the metric system, but is now outside the modern International System of Units (SI).[23] It is still commonly used in speech to measure real estate, in particular in Indonesia, India, and in various European countries.
In Russian and some other languages of the former Soviet Union, the are is called sotka (сотка: 'ahundred', i.e. 100m2 or 1/100 hectare). It is used to describe the size of suburban dacha or allotment garden plots or small city parks where the hectare would be too large. Many Russian dachas are 6 ares in size (in Russian, шесть соток).
Decare
The decare or dekare (/ˈdɛkɑːr,-ɛər/) is derived from deca and are, and is equal to 10 ares or 1000 square metres. It is used in Norway[24] and in the former Ottoman areas of the Middle East and Bulgaria[25] as a measure of land area. The names of the older land measures of similar size are usually used, redefined as exactly one decare:
The Unicode character U+33CA㏊SQUARE HA, in the CJK Compatibility block, is intended for compatibility with pre-existing East Asian character codes.[31] It is not intended for use in alphabetic contexts.
U+3336㌶SQUARE HEKUTAARU is a combination of ヘクタール (hekutāru), the Japanese translation of "hectare".
↑Caillard, Vincent Henry Penalver; Gibb, Elias John Wilkinson (1911). "Turkey". In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol.27 (11thed.). Cambridge University Press. pp.426–467, see page 442 second para. Two categories of rent, fixed and proportional, are payable to the state by mine-owners. The fixed rent is 10 piastres per jerib (about 10000 square metres), to be paid whether the mine is worked or not.
↑
Oscar van Vlijmen (11 September 2006). "Oppervlakte"[Area]. Eenheden, constanten en conversies [Units, constants and conversion] (in Dutch). Archived from the original on 19 June 2021. Retrieved 15 January 2011.
↑
Jacob de Gelder (1824). Allereerste Gronden der Cijferkunst[Introduction to Numeracy] (in Dutch). 's-Gravenhage and Amsterdam: de Gebroeders van Cleef. p.156. Retrieved 19 September 2012.
↑
Thierry Thomasset. "Le stère"(PDF). Tout sur les unités de mesure [All the units of measure] (in French). Université de Technologie de Compiègne. Archived from the original(PDF) on 21 July 2011. Retrieved 21 March 2011.
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