Rope Size Conversion Chart
American weight and measures are based on units used in Britain prior to 1864, when imperial system was officially established. The US law of 1866 set a relationship withwith the metric system by defining the meter as equal to 39.37 inches. Since then all measures were redefined in terms of metric units with the last minimal adjustment in 1959. However, the old standard of 1 foot was retained with the name US survey foot.