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# Hectare

The hectare (/ˈhɛktɛər, -tɑːr/; SI symbol: ha) is an SI accepted metric system unit of area equal to a square with 100-metre sides, or 10,000 m2, and is primarily used in the measurement of land.[1] There are 100 hectares in one square kilometre. An acre is about 0.405 hectare and one hectare contains about 2.47 acres.

In 1795, when the metric system was introduced, the "are" was defined as 100 square metres and the hectare ("hecto-" + "are") was thus 100 "ares" or 1⁄100 km2 (10,000 square metres). 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. The hectare, however, remains as a non-SI unit accepted for use with the SI units, mentioned in Section 4.1 of the SI Brochure as a unit whose use is "expected to continue indefinitely".[1]

The name was coined in French, from the Latin ārea.[2]

Comparison of area units
UnitSI
1 ca1 m2
1 a100 m2
1 ha10,000 m2
100 ha1,000,000 m21 km2
non-SI comparisons
non-SImetric
0.3861 sq mi1 km2
2.471 acre1 ha
107,639 sq ft1 ha
1 sq mi259.0 ha
1 acre0.4047 ha
Hectare
General information
Unit systemNon-SI unit accepted for use with SI
Unit ofArea
Symbolha
InSI base units:1 ha = 10 m

## 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:[3]

• The metre for length

• The are (100 m2) for area [of land]

• The stère (1 m3) for volume of stacked firewood[4]

• The litre (1 dm3) for volumes of liquid

• The gram for mass

In 1960, when the metric system was updated as the International System of Units (SI), the are did not receive international recognition. The International Committee for Weights and Measures (CIPM) makes no mention of the are in the current (2006) definition of the SI, but classifies the hectare as a "Non-SI unit accepted for use with the International System of Units".[5]

In 1972, the European Economic Community (EEC) passed directive 71/354/EEC,[6] 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.

## Units

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.

### Centiare

The centiare is one square metre.

### Deciare

The deciare is ten square metres.

### Are

The are (/ɑːr/[7] or /ɛər/[8]) is a unit of area, equal to 100 square metres (10 m × 10 m), 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).[9] It is still commonly used in colloquial speech to measure real estate, in particular in Indonesia, India, and in various European countries.

In Russian and other languages of the former Soviet Union, the are is called sotka (Russian: сотка: 'a hundred', i.e. 100 m2 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.

### Decare

The decare (/ˈdɛkɑːr, -ɛər/) is derived from deca and are, and is equal to 10 ares or 1000 square metres. It is used in Norway[10] and in the former Ottoman areas of the Middle East and the Balkans (Bulgaria)[11] as a measure of land area. Instead of the name "decare", the names of traditional land measures are usually used, redefined as one decare:

• Stremma in Greece[12]

• Dunam, dunum, donum, or dönüm in Israel, Palestine, Jordan, Lebanon, Syria and Turkey[13]

• Mål is sometimes used for decare in Norway, from the old measure of about the same area.

### Hectare

Trafalgar Square has an area of about one hectare.[14]

The hectare (/ˈhɛktɛər, -tɑːr/[15]), although not a unit of SI, is the only named unit of area that is accepted for use within the SI.[16] In practice the hectare is fully derived from the SI, being equivalent to a square hectometre. It is widely used throughout the world for the measurement of large areas of land, and it is the legal unit of measure in domains concerned with land ownership, planning, and management, including law (land deeds), agriculture, forestry, and town planning throughout the European Union.[17] The United Kingdom,[18] United States, Burma,[19][20] and to some extent Canada use the acre instead.

Some countries that underwent a general conversion from traditional measurements to metric measurements (e.g. Canada) required a resurvey when units of measure in legal descriptions relating to land were converted to metric units. Others, such as South Africa, published conversion factors which were to be used particularly "when preparing consolidation diagrams by compilation".[21]

In many countries, metrication 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:[22]

• Jerib

• Djerib in Turkey[23]

• Gong Qing (公頃/公顷 – gōngqǐng) in Hong Kong / mainland China

• Manzana

• Bunder in The Netherlands (until 1937)[24][25]

## Conversions

Metric and imperial/US customary comparisons ck
Metric equivalentsImperial/US customary equivalents
centiareca1 m20.01 a1.19599sq yd
area[26]100 ca100 m20.01 ha3.95369perches
decaredaa10 a1,000 m20.1 ha0.98842roods
hectareha[1]100 a**10,000 m2****0.01 km2**about 2.4710538 acres
square kilometrekm2100 ha1,000,000 m20.38610sq mi

The most commonly used units are in bold.

One hectare is also equivalent to:

• 1 square hectometre

• 15 mǔ or 0.15 qǐng[27]

• 10 dunam or dönüm (Middle East)[28]

• 10 stremmata (Greece)

• 6.25 rai (Thailand)[29]

• ≈ 1.008 chō (Japan)

• ≈ 2.381 feddan (Egypt)

## Visualising a hectare

### Interior of all-weather athletics track

• Conversion of units

• Hectometre

• Order of magnitude

## References

[1]
Citation Linkwww.bipm.orgBIPM (2014). "SI Brochure, Table 6". Retrieved 17 November 2014.
Sep 23, 2019, 7:00 PM
[2]
Citation Linkwww.oed.comOxford English Dictionary, 1st edition s.v.
Sep 23, 2019, 7:00 PM
[3]
Citation Linkaviatechno.free.fr"La loi du 18 Germinal an 3 " la mesure [républicaine] de superficie pour les terrains, égale à un carré de dix mètres de côté »" [The law of 18 Germanial year 3 "The [Republican] measure of land area equivalent to a ten-metre square"] (in French). Le CIV (Centre d'Instruction de Vilgénis) – Forum des Anciens. Retrieved 2 March 2010.
Sep 23, 2019, 7:00 PM
[4]
Citation Linkwww.utc.frThierry Thomasset. "Le stère" (PDF). Tout sur les unités de mesure [All the units of measure] (in French). Université de Technologie de Compiègne. Retrieved 21 March 2011.
Sep 23, 2019, 7:00 PM
[5]
Citation Linkwww.bipm.org"SI brochure (Chapter 4; Table 6)". International Bureau of Weights and Measures. 2006. Archived from the original on 1 October 2009. Retrieved 5 March 2010.
Sep 23, 2019, 7:00 PM
[6]
Citation Linkeur-lex.europa.eu"Council Directive of 18 October 1971 on the approximation of laws of the member states relating to units of measurement, (71/354/EEC)". Retrieved 7 February 2009.
Sep 23, 2019, 7:00 PM
[7]
Citation Linkoxforddictionaries.com"are". Oxford Dictionaries. Retrieved 24 December 2010.
Sep 23, 2019, 7:00 PM
[8]
Citation Linkwww.macmillandictionary.com"are – definition. American English definition of are by Macmillan Dictionary". Macmillandictionary.com. Retrieved 20 May 2012.
Sep 23, 2019, 7:00 PM
[9]
Citation Linkwww.bipm.org"SI brochure (8th edition)". BIPM. March 2006.
Sep 23, 2019, 7:00 PM
[10]
Citation Linkwww.ssb.no"Decrease in total grain yield". Grain and oil seeds, area and production, 2002. Statistics Norway. Retrieved 16 November 2010.
Sep 23, 2019, 7:00 PM
[11]
Citation Linkwww.bnr.bg"Market of agricultural land in Bulgaria". BNR Radio Bulgaria. 5 October 2010. Archived from the original on 22 October 2010. Retrieved 16 November 2010.
Sep 23, 2019, 7:00 PM
[12]
Citation Linkopenlibrary.orgΛεξικό της κοινής Νεοελληνικής (Dictionary of Modern Greek), Ινστιτούτο Νεοελληνικών Σπουδών, Θεσσαλονίκη, 1998. ISBN 960-231-085-5
Sep 23, 2019, 7:00 PM
[13]
Citation Linkbooks.google.comEl-Eini, Roza I.M. (2006). "Currency and Measures". Mandated landscape: British imperial rule in Palestine, 1929–1948. Routledge. p. xxiii. ISBN 978-0-7146-5426-3. Retrieved 5 May 2009.
Sep 23, 2019, 7:00 PM
[14]
Citation Linkwww.nao.org.uk"DEPARTMENT FOR ENVIRONMENT, FOOD AND RURAL AFFAIRS, AND RURAL PAYMENTS AGENCY; The Delays in Administering the 2005 Single Payment Scheme in England" (PDF). National Audit Office. 18 October 2006. p. 27.
Sep 23, 2019, 7:00 PM
[15]
Citation Linkoxforddictionaries.com"hectare". Oxford Dictionaries. Retrieved 24 December 2010.
Sep 23, 2019, 7:00 PM
[16]
Citation Linkwww.bipm.orgBureau international des poids et mesures (2006). "The International System of Units (SI)" (PDF). 8th ed. Retrieved 13 February 2008. Cite journal requires |journal= (help) Chapter 5.
Sep 23, 2019, 7:00 PM
[17]
Citation Linkeur-lex.europa.euThe Council of the European Communities (27 May 2009). "Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to Unit of measurement and on the repeal of Directive 71/354/EEC". Retrieved 29 January 2010.
Sep 23, 2019, 7:00 PM
[18]
Citation Linkwww.legislation.gov.uk"Weights and Measures Act 1985" (PDF). British Government. 1985. Retrieved 17 December 2016.
Sep 23, 2019, 7:00 PM
[19]
Citation Linkwww.cia.gov"Appendix G – Weights and Measures". The World Factbook. CIA. 2006. Retrieved 8 August 2006.
Sep 23, 2019, 7:00 PM
[20]
Citation Linkweb.archive.orgMYA/01/008 Agriculture Sectore Review, Working Paper No. 6 – Agroindustry in Myanmar Archived 15 May 2013 at the Wayback Machine
Sep 23, 2019, 7:00 PM