|Unit name||Ar / Are|
|Physical quantity (s)||Area|
|In SI units|
|In CGS units|
|Named after||Latin ārea , "area, area"|
|Derived from||square meters|
|See also: hectares|
The Ar , in Switzerland the Are , is a unit of area in the metric system of 100 m 2 with the unit symbol a (but often not or incorrectly abbreviated: Ar or ar). 100 a equals 1 ha . A square with an area of 1 a has an edge length of ten meters, which is why one speaks of a square decameter ( dam 2 ).
In the EU and Switzerland, the Ar or the Are is the legal unit for specifying the area of land and parcels.
In 1793, the meter was established in France as the 10 millionth part of the earth quadrant on the Parisian meridian . At the same time, the unit are based on the Latin word ārea (area, free space) for an area of 100 m 2 . It was initially the only metric unit of area in use, including its parts and multiples, centiares (1 ca = 1 m 2 ) and hectares (1 ha = 100 a).
In 1868 the unit of measurement was officially introduced in Germany under the name Ar: The corresponding North German order of measurements and weights came into force in 1872 for the entire German Empire.
Multiples and parts
- 1 hectare (from "hecto-ar") = 1 ha
- = 100 a = 10,000 m 2
- = 1 hm 2 = 100 m • 100 m
- 1 decar (from "Deka-Ar") = 1 daa
- = 10 a = 1000 m 2
- 1 ar
- = 1 a = 100 m 2
- = 1 dam 2 = 10 m • 10 m
- 1 centiar
- = 0.01 a = 1 m 2
- = 1 m 2 = 1 m • 1 m
Except for ares and hectares, these multiples and parts are uncommon in the German-speaking area and are only of historical interest.
- In Table 6 of the SI brochure (8th edition) the Ar is not mentioned. In the 7th edition from 1998 both are still included. In the 16th meeting of the CCU in 2004 ( memento from June 20, 2007 in the Internet Archive ) (page 11; PDF; 1.1 MB) it was stated that both should appear in Table 6. The Ar was then apparently eliminated as a “minor change” in an “editorial meeting”, which is referred to in the following 17th meeting ( memento of June 20, 2007 in the Internet Archive ) (page 5; PDF; 259 kB).
- C. Bopp: The international measure, weight and coin agreement through the metric system. Julius Maier, Stuttgart 1869.