An Inch Equals 2.54 Centimeters

The old UK inch divided from the Imperial Standard Yard equaled approximately 2.53998 centimeters. The US inch established by the the Mendenhall Order of April 5, 1893 was 1/39.37 of a meter, or approximately 2.540005 centimeters.

The international inch was standardized in 1959 at exactly 2.54 centimeters (although US land surveys continued to use the old inch as the "survey inch" until they were metricized).

http://home.att.net/~numericana/answer/units.htm

http://museum.nist.gov/exhibits/ex1/room4.html

http://www.sfei.org/ecoatlas/GIS/MapInterpretation/ConversionConstants.html

http://www.cofc.edu/~frysingj/background.htm

http://indykfi.phys.klte.hu/indyKFI/MT/langlo.htm