Metrication in the United States

White shampoos label measuring 23.7 FL OZ (700 mL)
A shampoo label from the U.S. that shows a round metric quantity taking secondary status in parentheses next to non-integer U.S. customary quantity

Metrication (or metrification) is the process of introducing the International System of Units, also known as SI units or the metric system, to replace a jurisdiction's traditional measuring units. U.S. customary units have been defined in terms of metric units since the 19th century,[1] 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.[2] However, conversion was not mandatory and many industries chose not to convert, and U.S. customary units remain in common use in many industries as well as in governmental use (for example, speed limits are still posted in miles per hour). There is government policy and metric (SI) program to implement and assist with metrication, however there is major social resistance for further metrication.[3][4][5]

Although customary units are used more often than metric units in the U.S., the SI system is used extensively in some fields such as science, medicine, electronics, the military, automobile production and repair, and international affairs.[6] Post-1994 federal law also mandates most packaged consumer goods be labeled in both customary and metric units.[7]

The U.S. has fully adopted the SI unit for time, the second.[8] The U.S. has a national policy to adopt the metric system.[3] All U.S. agencies are required to adopt the metric system.[9] As of January 2023, the U.S. government had retired the survey foot.[10]

  1. ^ Bearce, Henry Walter (May 21, 1926). "A Fundamental Basis for Measurements of Length" (PDF). Scientific Papers of the Bureau of Standards. 21 (S535): 396. doi:10.6028/nbsscipaper.221. Archived (PDF) from the original on December 6, 2020. Retrieved December 17, 2023. In the United States the basic relation officially recognized is that contained in the law of July 28, 1866, and set forth in the Mendenhall order of April 5, 1893; namely...
  2. ^ "Metric Conversion Act of 1975". U.S. Metric Association. June 25, 2022.
  3. ^ a b "Metric (SI) Program". NIST. February 5, 2015.
  4. ^ "Why the Metric System Has a Place in U.S. Schools". The Atlantic. June 16, 2016.
  5. ^ "Why Won't America Go Metric?". December 15, 2014.
  6. ^ "The United States and the Metric System" (PDF). Toward a Metric America. US Metric Association. p. 3. Archived (PDF) from the original on February 17, 2023. Retrieved December 17, 2023. Also, our scientific and medical communities use metric units almost exclusively.
  7. ^ "FTC Proposes to Require Labels to Include Metric Measurement". Federal Trade Commission. December 19, 2013. Retrieved August 2, 2017.
  8. ^ Benham, Elizabeth (October 6, 2020). "Busting Myths about the Metric System". NIST.
  9. ^ "Executive Order 12770 – US Metric Association". usma.org. Retrieved October 22, 2023.
  10. ^ "U.S. Survey Foot". NIST. July 26, 2019.