Hectare · Lablypedia

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 or ⁠1/100⁠ km² (10000 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, 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.

Description

The name was coined in French, from the Latin ārea. The hectare is equivalent to 10,000 square metres (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 some domains concerned with land ownership, planning, and management, including law (land deeds), agriculture, forestry, and town planning throughout the European Union, South Africa, New Zealand, Australia, Canada and the United Kingdom. However, the United States and Myanmar (Burma) 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:

Jerib (Persian: جریب) in Iran
Djerib (Turkish: cerip) in Turkey
Gongqing (traditional Chinese: 公頃; simplified Chinese: 公顷; pinyin: gōngqǐng) in China
Manzana in Argentina
Bunder in the Netherlands (until 1937)

In Mexico, land area measurements are commonly given as combinations of hectares, ares, and centiares. 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 (12100.26 m²).

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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:

The metre for length
The are (100 m²) for area [of land]
The stère (1 m³) for volume of stacked firewood
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 () used to classify the hectare as a "Non-SI unit accepted for use with the International System of Units" but As of 2026, the International Bureau of Weights and Measures (BIPM) no longer describes it and other widely used non-SI units as accepted.

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 (dma, sometimes seen in cadastre area evaluation of real estate plots) is ⁠1/10,000⁠ are or one square decimetre. Such usage of a double prefix is non-standard. The decimilliare is (100 mm)² or roughly a four-inch-by-four-inch square. (The decimilliare is smaller by approximately 3.1%.)

Centiare

The centiare is one square metre.

Deciare

The deciare (rarely used) is ten square metres.

Are

The are (, ) 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). 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: '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. Many Russian dachas are 6 ares in size (in Russian, шесть соток).

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. The names of the older land measures of similar size are usually used, redefined as exactly one decare:

Stremma in Greece
Dunam, dunum, dulum, donum, or dönüm in the Balkans, Israel, Palestine, Jordan, Lebanon, Syria, and Turkey
Mål in Norway.

Conversions

The most commonly used units are in bold.

One hectare is also equivalent to:

1 square hectometre
1.008 chō (Japan)
2.381 feddan (Egypt)
6.25 rai (Thailand)
10 dunam or dönüm (Middle East)
10 stremmata (Greece)
15 mǔ or 0.15 qǐng

Unicode

The Unicode character U+33CA ㏊ SQUARE HA, in the CJK Compatibility block, is intended for compatibility with pre-existing East Asian character codes. 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".