A decametre (International spelling as used by the International Bureau of Weights and Measures[1][2]) or dekameter (American spelling[3]), symbol dam (sometimes unofficially Dm or dkm), is a unit of length in the metric system equal to ten metres; it is very rarely used.

Unit systemmetric
Unit oflength
1 dam in ...... is equal to ...
   SI units   10 m
   imperial/US units   10.936 yd
393.70 in

This measure is included in the SI mostly for completeness: in principle, any combination of prefix and unit can be written, but many are rarely used in practice. One practical use of the decametre is for altitude of geopotential heights in meteorology. Meteorologists also use another seldom encountered SI prefix: hecto- in hectopascal (hPa). The volumetric form cubic decametre is convenient for describing large volumes of water such as in rivers and lakes. A cubic decametre (dam3) is equivalent to one megalitre (ML).

The square decametre (dam2), also known as the are (a), is the basis for the hectare (100 dam2), the standard metric unit of land registry.

One technical atmosphere is equal to the pressure of one decameter of water.

See also


  1. Decimal multiples and submultiples of SI units, 2006, SI Brochure: The International System of Units (SI), 8th edition
  2. Unit of length (metre), 2006, SI Brochure: The International System of Units (SI), 8th edition
  3. The Two Classes of SI Units and the SI Prefixes, 2008, The NIST Guide for the Use of the International System of Units
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