United States customary units

United States customary units (often incorrectly referred to as imperial units)^[1] form a system of measurement units commonly used in the United States and most U.S. territories,^[2] since being standardized and adopted in 1832.^[3] The United States customary system developed from English units that were in use in the British Empire before the U.S. became an independent country. The United Kingdom's system of measures was overhauled in 1824 to create the imperial system (with imperial units), which was officially adopted in 1826, changing the definitions of some of its units. Consequently, while many U.S. units are essentially similar to their imperial counterparts, there are noticeable differences between the systems.

The majority of U.S. customary units were redefined in terms of the meter and kilogram with the Mendenhall Order of 1893 and, in practice, for many years before.^[4] These definitions were refined by the international yard and pound agreement of 1959.^[5]

The United States uses customary units in commercial activities, as well as for personal and social use. In science, medicine, many sectors of industry, and some government and military areas, metric units are used. The International System of Units (SI), the modern form of the metric system, is preferred for many uses by the U.S. National Institute of Standards and Technology (NIST).^[6] For newer types of measurement where there is no traditional customary unit, international units are used, sometimes mixed with customary units: for example, electrical resistance of wire expressed in ohms (SI) per thousand feet.

^
Attributed to multiple references:
- Kaplan, Sarah (September 19, 2017). "Pirates — yes, pirates — may be why the U.S. doesn't use the metric system". The Washington Post. ISSN 0190-8286. Archived from the original on September 19, 2017. Retrieved February 25, 2024. As the rest of the world adopted the metric system, the United States continued to bumble around with unwieldy imperial units. Aaaarrrgh!
- Badshah, Nadeem (May 28, 2022). "Boris Johnson to reportedly bring back imperial measurements to mark platinum jubilee". The Guardian. ISSN 0261-3077. Archived from the original on May 28, 2022. Retrieved February 25, 2024. Only three other countries, the US, Myanmar and Liberia, use the imperial system on a daily basis.
- Vlamis, Kelsey (September 18, 2021). "Britain may revert to the imperial system as part of its plans to 'capitalize on new Brexit freedoms'". Business Insider. Archived from the original on September 18, 2021. Retrieved February 25, 2024. Most of the world uses the metric system of weights and measurements. The US uses the imperial system.
- Condliffe, Jamie (January 2, 2013). "It's Time For the US to Go Metric". Gizmodo. Archived from the original on June 11, 2019. Retrieved February 25, 2024. The US has a love affair with imperial units: height in inches, milk in quarts, weight in pounds. You name it, and it's measured in imperial. The only problem? Imperial is dumb.
- Nicholson, Kate (September 17, 2021). "Why The Difference Between Imperial And Metric Systems Matters". The Huffington Post. Archived from the original on September 17, 2021. Retrieved February 25, 2024. Myanmar, Liberia and the US are currently the only countries in the world to use the imperial system.
- Reichhardt, Tony (October 7, 1999). "NASA reworks its sums after Mars fiasco". Nature. 401 (517). doi:10.1038/43974. ISSN 0028-0836. Archived from the original on June 3, 2018. Retrieved February 25, 2024. While virtually all scientists use metric units, many US engineers, both inside and outside the space programme, use imperial units, converting them when necessary.
^ "US leaves the world puzzled by dragging its feet on metric system". The Nation Thailand. December 26, 2015. Retrieved January 28, 2023.^{[better source needed]}
^ Barbrow, L.E. and Judson, L. V. (1976) Weights and Measures of the United States. National Bureau of Standards Special Publication 447. p. 5–6
^ T.C. Mendenhall, Superintendent of Standard Weights and Measures. Order of April 5, 1893 Archived September 30, 2012, at the Wayback Machine, published as Appendix 6 to the Report for 1893 of the United States Coast and Geodetic Survey.
^ Astin, A.V., Karo, H.A. and Mueller, F.H. (June 25, 1959). Doc 59-5442, "Refinement of Values for the Yard and the Pound." Federal Register. Note that 999,998 = 3937 × 254.
^ Laws and Metric Program. U.S. National Institute of Standards and Technology, 2010

[1] Attributed to multiple references:
Kaplan, Sarah (September 19, 2017). "Pirates — yes, pirates — may be why the U.S. doesn't use the metric system". The Washington Post. ISSN 0190-8286. Archived from the original on September 19, 2017. Retrieved February 25, 2024. As the rest of the world adopted the metric system, the United States continued to bumble around with unwieldy imperial units. Aaaarrrgh!
Badshah, Nadeem (May 28, 2022). "Boris Johnson to reportedly bring back imperial measurements to mark platinum jubilee". The Guardian. ISSN 0261-3077. Archived from the original on May 28, 2022. Retrieved February 25, 2024. Only three other countries, the US, Myanmar and Liberia, use the imperial system on a daily basis.
Vlamis, Kelsey (September 18, 2021). "Britain may revert to the imperial system as part of its plans to 'capitalize on new Brexit freedoms'". Business Insider. Archived from the original on September 18, 2021. Retrieved February 25, 2024. Most of the world uses the metric system of weights and measurements. The US uses the imperial system.
Condliffe, Jamie (January 2, 2013). "It's Time For the US to Go Metric". Gizmodo. Archived from the original on June 11, 2019. Retrieved February 25, 2024. The US has a love affair with imperial units: height in inches, milk in quarts, weight in pounds. You name it, and it's measured in imperial. The only problem? Imperial is dumb.
Nicholson, Kate (September 17, 2021). "Why The Difference Between Imperial And Metric Systems Matters". The Huffington Post. Archived from the original on September 17, 2021. Retrieved February 25, 2024. Myanmar, Liberia and the US are currently the only countries in the world to use the imperial system.
Reichhardt, Tony (October 7, 1999). "NASA reworks its sums after Mars fiasco". Nature. 401 (517). doi:10.1038/43974. ISSN 0028-0836. Archived from the original on June 3, 2018. Retrieved February 25, 2024. While virtually all scientists use metric units, many US engineers, both inside and outside the space programme, use imperial units, converting them when necessary.

[2] Kaplan, Sarah (September 19, 2017). "Pirates — yes, pirates — may be why the U.S. doesn't use the metric system". The Washington Post. ISSN 0190-8286. Archived from the original on September 19, 2017. Retrieved February 25, 2024. As the rest of the world adopted the metric system, the United States continued to bumble around with unwieldy imperial units. Aaaarrrgh!

[3] Badshah, Nadeem (May 28, 2022). "Boris Johnson to reportedly bring back imperial measurements to mark platinum jubilee". The Guardian. ISSN 0261-3077. Archived from the original on May 28, 2022. Retrieved February 25, 2024. Only three other countries, the US, Myanmar and Liberia, use the imperial system on a daily basis.

[4] Vlamis, Kelsey (September 18, 2021). "Britain may revert to the imperial system as part of its plans to 'capitalize on new Brexit freedoms'". Business Insider. Archived from the original on September 18, 2021. Retrieved February 25, 2024. Most of the world uses the metric system of weights and measurements. The US uses the imperial system.

[5] Condliffe, Jamie (January 2, 2013). "It's Time For the US to Go Metric". Gizmodo. Archived from the original on June 11, 2019. Retrieved February 25, 2024. The US has a love affair with imperial units: height in inches, milk in quarts, weight in pounds. You name it, and it's measured in imperial. The only problem? Imperial is dumb.

[6] Nicholson, Kate (September 17, 2021). "Why The Difference Between Imperial And Metric Systems Matters". The Huffington Post. Archived from the original on September 17, 2021. Retrieved February 25, 2024. Myanmar, Liberia and the US are currently the only countries in the world to use the imperial system.

[7] Reichhardt, Tony (October 7, 1999). "NASA reworks its sums after Mars fiasco". Nature. 401 (517). doi:10.1038/43974. ISSN 0028-0836. Archived from the original on June 3, 2018. Retrieved February 25, 2024. While virtually all scientists use metric units, many US engineers, both inside and outside the space programme, use imperial units, converting them when necessary.

[2] "US leaves the world puzzled by dragging its feet on metric system". The Nation Thailand. December 26, 2015. Retrieved January 28, 2023.^{[better source needed]}

[3] Barbrow, L.E. and Judson, L. V. (1976) Weights and Measures of the United States. National Bureau of Standards Special Publication 447. p. 5–6

[Mendenhall-4] T.C. Mendenhall, Superintendent of Standard Weights and Measures. Order of April 5, 1893 Archived September 30, 2012, at the Wayback Machine, published as Appendix 6 to the Report for 1893 of the United States Coast and Geodetic Survey.

[FR59-5442-5] Astin, A.V., Karo, H.A. and Mueller, F.H. (June 25, 1959). Doc 59-5442, "Refinement of Values for the Yard and the Pound." Federal Register. Note that 999,998 = 3937 × 254.

[6] Laws and Metric Program. U.S. National Institute of Standards and Technology, 2010

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