|+Comparison of Area units
!Unit||nearest SI||SI base
|-align="right"
|1 ca
|1 m²
|1 m²
|-align="right"
|1 a
|1 dam²
|10² m²
|-align="right"
|1 ha
|1 hm²
|104 m²
|-align="right"
|100 ha
|1 km²
|106 m²
|-
!colspan="3"|non-SI comparisons
|-
!non-SI||metric||SI base
|-align="right"
|119.6 sq yard
|1 a
|102 m²
|-align="right"
|1076.39 sq ft
|1 a
|102 m²
|
An
are (symbol
a, ) 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 of the modern
International System (SI). It is accepted, but not encouraged, for use with the SI.
It is commonly used in many countries—in particular, in
French-,
Portuguese-,
Polish-
Dutch- and
German-speaking countries—to measure real estate; elsewhere, the square metre is usually used. The are is sometimes used in combination with the centiare, ''e.g.'' "10 ares 12 centiares" = 1012 m². Larger land areas are generally measured in
hectares. The
decare is commonly used in the former
Ottoman countries, usually under local names. Other
prefixes for multiples and submultiples of the ''are'' are not in common use. There are other local units which are exact multiples of the are, ''e.g.'' the
Thai rai, 16 a.
The are is the standard unit of measurement for private plots of land (as opposed to large industrial and agricultural properties) in Russia and all the countries of the former Soviet Union. But since the original root word "are" has never been in use in Russian, and only the word "hectare" exists as a unit of land measurement, the Russian word for "are" is "sotka" (сотка), which roughly translates as "hundredth". Thus, the Russian language regards the hectare as the "root" unit of measurement, and a "sotka" is essentially a "centihectare", or (are x 100 ÷ 100)! City dwellers in the former USSR use the term "sotka" to describe the size of their suburban
dacha or
allotment garden plots or small city parks; country dwellers or wealthy suburban homeowners use it to describe the size of the private yards around their houses, small private orchards, and the like. Hectares are used to describe larger plots of land, such as a factory complex, a collective farm, a university campus, a nature preserve, or the country's lone golf course.