Are (a)

Metric (SI)Traditional unit (still used in some regions)

100 square meters, a square 10 m on a side. Mostly replaced by the hectare (100 ares).

1 are = 100 square meters (exactly).

About the are

Latin area, meaning an open piece of ground, gave French the word are, the base land unit of the metric system. A French law of 1795 defined it as 100 square meters, a square ten meters on each side, and the hectare was then built as 100 ares, which is why that familiar unit carries the "hecto-" prefix.

The are itself never made it into the modern SI when the system was rationalised in 1960, and the hectare took over for fields, forests and planning. The are survives mostly as a convenience for small plots such as building lots and gardens, and in everyday talk in parts of continental Europe. NIST lists it as exactly 100 square meters, so the figure used here is firm, and 100 ares make one hectare. The hectare is about 2.47 acres, so an are is roughly a fortieth of an acre.

Sources: Wikipedia: Hectare; NIST SP 811, Appendix B.8 conversion factors

Are conversion chart

1 are expressed in every other area unit:

More Metric (SI) units

• square meter (area)
• square kilometer (area)
• hectare (area)
• square centimeter (area)
• square millimeter (area)
• meter (length)
• kilometer (length)
• centimeter (length)
• millimeter (length)
• micrometer (length)
• nanometer (length)
• picometer (length)
• decimeter (length)
• hectometer (length)
• decameter (length)
• kilogram (weight & mass)

All Metric (SI) units

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