Metric is currently the “ preferred system of weights and measures for United States trade and commerce” https://uscode.house.gov/view.xhtml;jsessionid=8314B6B

Metric is currently the “ preferred system of weights and measures for United States trade and commerce” https://uscode.house.gov/view.xhtml;jsessionid=8314B6B7A95CC66743496CA05FED62D5?hl=false&edition=prelim&req=granuleid%3AUSC-prelim-title15-section205b&num=0&saved=%7CZ3JhbnVsZWlkOlVTQy1wcmVsaW0tdGl0bGUxNS1zZWN0aW9uMjA1YQ%3D%3D%7C%7C%7C0%7Cfalse%7Cprelim https://uscode.house.gov/view.xhtml;jsessionid=8314B6B7A95CC... As you mentioned, the foot and all other U.S. customary units are based on the International System of Units (SI). https://www.nist.gov/pml/weights-and-measures/metric-si https://www.nist.gov/pml/weights-and-measures/metric-si