Except the US uses the Metric system > U.S. customary units have been defined in terms of metric units since the 19th century, and the SI has been the "preferr

Except the US uses the Metric system > U.S. customary units have been defined in terms of metric units since the 19th century, and the SI has been the "preferred system of weights and measures for United States trade and commerce" since 1975 according to United States law.[1] [1] https://en.wikipedia.org/wiki/Metrication_in_the_United_States https://en.wikipedia.org/wiki/Metrication_in_the_United_Stat...