The hectare (;
SI symbol: ha) is a
non-SI metric unit
The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Internati ...
of
area equal to a square with 100-
metre sides (1 hm
2), or 10,000 m
2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An
acre is about and one hectare contains about .
In 1795, when the metric system was introduced, the ''are'' was defined as 100
square metres, or one square
decametre
A decametre ( International spelling as used by the International Bureau of Weights and Measures and by most English speaking countries, United States spelling dekameter or decameter,), symbol dam ("da" for the SI prefix deca-, "m" for the SI ...
, and the hectare ("
hecto-
''Hecto'' (symbol: h) is a decimal unit prefix in the metric system denoting a factor of one hundred. It was adopted as a multiplier in 1795, and comes from the Greek , meaning "hundred". In 19th century English it was sometimes spelled "hecato", ...
" + "are") was thus 100 ''ares'' or km
2 (10,000 square metres). When the metric system was further rationalised in 1960, resulting in the
International System of Units (), the ''are'' was not included as a recognised unit. The hectare, however, remains as a non-SI unit accepted for use with the SI and whose use is "expected to continue indefinitely". Though the dekare/decare daa (1,000 m
2) and are (100 m
2) are not officially "accepted for use", they are still used in some contexts.
Description
The hectare (), although not a unit of SI, is the only named unit of area that is
accepted for use with SI units.
[ Chapter 5.] The name was coined in French, from the Latin ''ārea''. 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
Urban planning, also known as town planning, city planning, regional planning, or rural planning, is a technical and political process that is focused on the development and design of land use and the built environment, including air, water, ...
throughout the
European Union
The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been de ...
and
Australia (since 1970).
However, the United Kingdom, United States, Burma,
[
] 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".
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:
*''
Jerib
The jerib or djerib ( fa, جریب; tr, cerip) is a traditional unit of land measurement in the Middle East and southwestern Asia. It is a unit of area used to measure land holdings (real property) in much the way that an acre or hectare are. ...
'' ( fa, جریب) in
Iran
*''
Djerib'' ( tr, cerip) in
Turkey
*''Gongqing'' () in
China
*''
Manzana'' in
Argentina
*''
Bunder
A bunder or bonnier is an obsolete unit of area previously used in the Low Countries
The term Low Countries, also known as the Low Lands ( nl, de Lage Landen, french: les Pays-Bas, lb, déi Niddereg Lännereien) and historically called the Net ...
'' in the
Netherlands (until 1937)
History
The metric system of measurement was first given a legal basis in 1795 by the
French Revolution
The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in coup of 18 Brumaire, November 1799. Many of its ...
ary government. The law of
18 Germinal, Year III (7 April 1795) defined five units of measure:
*The
:metre for length
*The
are (100 m
2) for area
f land*The
stère (1 m
3) for volume of stacked firewood
*The
:litre (1 dm
3) for volumes of liquid
*The
gram
The gram (originally gramme; SI unit symbol g) is a unit of mass in the International System of Units (SI) equal to one one thousandth of a kilogram.
Originally defined as of 1795 as "the absolute weight of a volume of pure water equal to th ...
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
The General Conference on Weights and Measures (GCWM; french: Conférence générale des poids et mesures, CGPM) is the supreme authority of the International Bureau of Weights and Measures (BIPM), the intergovernmental organization established i ...
() 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".
In 1972, the
European Economic Community (EEC) passed directive 71/354/EEC, 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
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 (sometimes seen in
cadastre area evaluation of real estate plots) is are or one square decimetre.
Centiare
The centiare is one square metre.
Deciare
The deciare (rarely used) is ten square metres.
Are
The are ( or ) is a unit of area, equal to 100 square metres (), 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). It is still commonly used in speech to measure real estate, in particular in Indonesia, India, and in various European countries.
In
Russian
Russian(s) refers to anything related to Russia, including:
*Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries
*Rossiyane (), Russian language term for all citizens and peo ...
and some other languages of the former
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
, the ''are'' is called (russian: link=no, сотка: 'a hundred', i.e. 100 m
2 or hectare). It is used to describe the size of suburban
dacha
A dacha ( rus, дача, p=ˈdatɕə, a=ru-dacha.ogg) is a seasonal or year-round second home, often located in the exurbs of post-Soviet countries, including Russia. A cottage (, ') or shack serving as a family's main or only home, or an outbu ...
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, ).
Decare
The decare or dekare () is derived from ''
deca'' and ''are'', and is equal to 10 ares or 1000 square metres. It is used in
Norway and in the former
Ottoman areas of the
Middle East and
Bulgaria as a measure of land area. Instead of the name "decare", the names of traditional land measures are usually used, redefined as one decare:
* in
Greece
Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders ...
* in the
Balkans,
Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
,
Palestine,
Jordan,
Lebanon,
Syria and
Turkey
* is used for decare in Norway, from the old measure of about the same area.
Conversions
The most commonly used units are in bold.
One hectare is also equivalent to:
* 1 square hectometre
* 15
mǔ or 0.15 qǐng
* 10
dunam or dönüm (Middle East)
* 10
stremma
The stremma ( stremmata; el, στρέμμα, ''strémma'') is a Greek unit of land area equal to 1,000 square metres. Historically, stremmata were not standardized, and may have been anywhere from .
History
The ancient Greek equivalent was the s ...
ta (Greece)
* 6.25
rai
RAI – Radiotelevisione italiana (; commercially styled as Rai since 2000; known until 1954 as Radio Audizioni Italiane) is the national public broadcasting company of Italy, owned by the Ministry of Economy and Finance. RAI operates many ter ...
(
Thailand)
* approximately 1.008
chō
is a Japanese actor and narrator from Kōnosu, Saitama. His former stage name was . He is a graduate of the Nishogakusha University Department of Literature and received training at Bungakuza's research establishment and the Seinenza Theater C ...
(
Japan)
* approximately 2.381
feddan
A feddan ( ar, فدّان, faddān) is a unit of area used in Egypt, Sudan, Syria, and the Oman. In Classical Arabic, the word means 'a yoke of oxen', implying the area of ground that could be tilled by oxen in a certain time. In Egypt, the fedda ...
(
Egypt
Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Medit ...
)
See also
*
Conversion of units
Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors which change the measured quantity value without changing its effects.
Overview
The process ...
*
Hectometre
The hectometre ( International spelling as used by the International Bureau of Weights and Measures; SI symbol: hm) or hectometer (American spelling) is a unit of length in the International System of Units (SI), equal to one hundred metres and t ...
*
Order of magnitude
References
External links
Official SI website: Table 6. Non-SI units accepted for use with the International System of Units
{{Use dmy dates, date=June 2016
Units of area
Non-SI metric units