The foot is defined as 12 inches, each inch is 25.4 millimeters. A meter is defined as "the length of the path travelled by light in vacuum during a time interv

The foot is defined as 12 inches, each inch is 25.4 millimeters. A meter is defined as "the length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second." So the foot is defined in terms of exact rational seconds. NIST offers calibration and measurement services for length. http://nist.gov/calibrations/dimensional_links.cfm http://nist.gov/calibrations/dimensional_links.cfm "Traceability to NIST" http://nist.gov/traceability/index.cfm http://nist.gov/traceability/index.cfm is a big deal to people who care about calibration in the US. NIST and other national calibration labs circulate "transfer standards" amongst each other in order to ensure international agreement.