View source for United States customary units

{{short description|System of units of measurement commonly used in the United States}}
{{distinguish|Imperial units}}
{{Use American English|date=September 2020}}
{{Use mdy dates|date=February 2024|cs1-dates=ll}}
[[File:Metric_and_imperial_systems_(2019).svg|thumb|upright=1.35|Countries using the [[Metric system|metric]] ([[International System of Units|SI]]), [[Imperial units|imperial]], and US customary systems as of 2019]]

'''United States customary units''' form a system of [[Units of measurement|measurement units]] commonly used in the [[United States]] and most [[Territories of the United States|U.S. territories]]<ref>{{Cite web |last= |first= |title=US leaves the world puzzled by dragging its feet on metric system |url=https://www.nationthailand.com/perspective/30275741 |date=December 26, 2015 |access-date=January 28, 2023 |website=The Nation Thailand}}{{Better source needed|date=January 2023}}</ref> since being standardized and adopted in 1832.<ref>Barbrow, L.E. and Judson, L. V. (1976) [https://www.govinfo.gov/content/pkg/GOVPUB-C13-691a9b38e29a85d0925f4db586b60735/pdf/GOVPUB-C13-691a9b38e29a85d0925f4db586b60735.pdf ''Weights and Measures of the United States'']. National Bureau of Standards Special Publication 447. p. 5&ndash;6</ref> 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 evolved by 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 [[comparison of the imperial and US customary measurement systems|differences between the systems]].

The majority of U.S. customary units were redefined in terms of the [[metre|meter]] and [[kilogram]] with the [[Mendenhall Order]] of 1893 and, in practice, for many years before.<ref name="Mendenhall">[[Thomas Corwin Mendenhall|T.C. Mendenhall]], Superintendent of Standard Weights and Measures. [http://physics.nist.gov/Pubs/SP447/app3.pdf Order of April 5, 1893] {{webarchive |url=https://web.archive.org/web/20120930180925/http://physics.nist.gov/Pubs/SP447/app3.pdf |date=September 30, 2012}}, published as Appendix&nbsp;6 to the Report for 1893 of the [[United States Coast and Geodetic Survey]].</ref> These definitions were refined by the [[international yard and pound]] agreement of 1959.<ref name="FR59-5442">Astin, A.V., Karo, H.A. and Mueller, F.H. (June 25, 1959). Doc 59-5442, "[http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf Refinement of Values for the Yard and the Pound]." ''[[Federal Register]]''. Note that 999,998 = 3937 × 254.</ref>

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).<ref>[https://www.nist.gov/pml/wmd/metric/index.cfm Laws and Metric Program]. U.S. National Institute of Standards and Technology, 2010</ref> 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 [[ohm]]s (SI) per thousand feet.

==History==
{{See also|Imperial and US customary measurement systems|Comparison of the imperial and US customary measurement systems}}

The United States customary system of units of 1832 is based on the system in use in the United Kingdom prior to the introduction to the British [[Imperial units|imperial system]] on January 1, 1826.<ref>"English units of measurement". ''The Columbia Encyclopedia'' 6th ed. 2001-2007. [https://web.archive.org/web/20080714214207/http://www.bartleby.com/65/en/Englsh-u.html archived copy].</ref> Both systems are derived from [[English units]], an older system of units which had evolved over the millennia before [[American independence]], and which had its roots in both [[Roman units|Roman]] and [[English units|Anglo-Saxon]] units.

The customary system was championed by the U.S.-based International Institute for Preserving and Perfecting Weights and Measures in the late 19th century. Some advocates of the customary system saw the French Revolutionary, or metric, system as atheistic. The president of an Ohio auxiliary of the Institute wrote that the traditional units were "a just weight and a just measure, which alone are acceptable to the Lord". His organization later went so far as to publish music for a song proclaiming "down with every 'metric' scheme".<ref name="Gardner">{{cite book |author=Martin Gardner |title=Fads and Fallacies in the Name of Science |url=https://books.google.com/books?id=X0HCAgAAQBAJ&pg=PA180 |date=May 4, 2012 |publisher=Courier Corporation |isbn=978-0-486-13162-7 |pages=180–}}</ref>

The U.S. government passed the [[Metric Conversion Act]] of 1975, which made the [[metric system]] "the preferred system of weights and measures for U.S. trade and commerce". The legislation states that the federal government has a responsibility to assist industry as it ''voluntarily'' converts to the metric system, i.e., [[Metrication in the United States|metrification]]. This is most evident in U.S. labeling requirements on food products, where SI units are almost always presented alongside customary units. According to the ''[[CIA World Factbook]]'', the United States is one of three nations (along with [[Liberia]] and [[Myanmar (Burma)]]) that have not adopted the metric system as their official system of weights and measures.<ref name="CIA_World_Factbook">{{Cite book |chapter-url=https://www.cia.gov/the-world-factbook/references/weights-and-measures/ |title=The World Factbook |publisher=[[Central Intelligence Agency]] |location=Washington, D.C. |chapter=References - Weights and Measures |access-date=April 22, 2021}}</ref>

[[s:Executive Order 12770|Executive Order 12770]], signed by President [[George H. W. Bush]] on July 25, 1991, citing the Metric Conversion Act, directed departments and agencies within the [[Executive (government)|executive branch]] of the [[United States Government]] to "take all appropriate measures within their authority" to use the metric system "as the preferred system of weights and measures for United States trade and commerce" and authorized the [[United States Secretary of Commerce|Secretary of Commerce]] "to charter an Interagency Council on Metric Policy ('ICMP'), which will assist the Secretary in coordinating Federal Government-wide implementation of this order."

U.S. customary units are widely used on consumer products and in industrial manufacturing. Metric units are standard in the fields of science, medicine, and engineering, as well as many sectors of industry and government, including the [[U.S. armed forces|military]].<ref name=CIA_World_Factbook/> There are anecdotal objections to the use of metric units in [[carpentry]] and the building trades, on the basis that it is easier to remember an integer number of inches plus a fraction, rather than a measurement in millimeters,<ref>Robyn Williams (February 8, 1998) [http://www.abc.net.au/radionational/programs/ockhamsrazor/trouble-with-the-metric-system/3552102 "Trouble with the Metric System"]. Australian ''Radio National'', Ockham's Razor.</ref> or that foot-inch measurements are more suitable when distances are frequently divided into halves, thirds, and quarters, often in parallel. The metric system also lacks a parallel measurement to the [[Foot (unit)|foot]].<ref name="Tenner">Ed Tenner, (May 2005). [https://www.technologyreview.com/2005/05/01/39811/the-trouble-with-the-meter/ "The Trouble with the Meter"]. Technologyreview.com.</ref>

The term "United States customary units" was used by the former [[United States National Bureau of Standards]],<ref>{{cite book |author=<!--Not stated--> |date=1960 |title=Units of Weight and Measure (United States Customary and Metric}: Definitions and Tables of Equivalents |url=https://books.google.com/books?id=ejpUAAAAYAAJ&pg=PA1 |location=Washington DC |publisher=United States National Bureau of Standards |page=1 }}</ref> although "English units" is sometimes used in colloquial speech.<ref>{{cite journal |author=<!--Not stated--> |title=Policy for NBS usage of SI Units |page=18 |date=January 1971 |journal=Technical News Bulletin |url=https://books.google.com/books?id=Efah8_3glg4C&pg=PA18 |volume=55 |issue=1 |location=Washington DC |publisher=United States National Bureau of Standards }}</ref>

==Length==
For measuring length, the U.S. customary system uses the [[inch]], [[Foot (length)|foot]], [[yard]], and [[mile]], which are the only four customary length measurements in everyday use. From 1893, the foot was legally defined as exactly {{nowrap|{{frac|1200|3937}} {{val||ul=meter}}}} (approximately {{val|0.3048006|u=m}}).<ref name=":1" /> Since July 1, 1959, the units of length have been defined on the basis of {{val|1|ul=yard}} = {{val|0.9144|u=m}}.<ref name="FR59-5442" /> The U.S., the [[United Kingdom]] and other [[Commonwealth of Nations|Commonwealth]] countries agreed on this definition per the [[International yard and pound|International Yard and Pound Agreement]] of 1958. At the time of the agreement, the basic [[geodetic datum]] in North America was the [[North American Datum]] of 1927 (NAD27), which had been constructed by [[triangulation]] based on the definition of the foot in the [[Mendenhall Order]] of 1893, that is {{val|1|ul=foot}} = {{nowrap|{{frac|1200|3937}} {{val||ul=meter}}}}: this definition was retained for data derived from NAD27, but renamed the ''US survey foot'' to distinguish it from the international foot.<ref name="FR59-5442" /> For most applications, the difference between the two definitions is insignificant – one international foot is exactly {{val|0.999998}} of a US survey foot, for a difference of about {{cvt|1/8|in|mm|0}} per mile – but it affects the definition of the [[State Plane Coordinate System]]s (SPCSs), which can stretch over hundreds of miles.<ref name="NGS-FAQ">{{Cite web|title=Frequently Asked Questions about the National Geodetic Survey|url=http://www.ngs.noaa.gov/faq.shtml#Feet|access-date=May 16, 2009|work=[[National Geodetic Survey]]}}</ref>

The NAD27 was replaced in the 1980s by the North American Datum of 1983 (NAD83), which is defined in meters. The SPCSs were also updated, but the [[U.S. National Geodetic Survey]] left the decision of which (if any) definition of the foot to use to the individual states (and other jurisdictions). All SPCS 1983 systems are defined in meters, but forty jurisdictions also use the survey foot, six use the international foot, and ten do not specify which, if any, foot type should be used.<ref>{{Cite web| title = State Plane Coordinate System of 1983: legislation and foot version| date=n.d.| access-date = February 25, 2024| url = https://geodesy.noaa.gov/SPCS/images/spcs83-legislation-feet.png}}</ref>

In 2019, the NIST, working with the National Geodetic Survey (NGS), National Ocean Service (NOS), National Oceanic and Atmospheric Administration (NOAA) and  Department of Commerce (DOC), issued a Federal Register Notice (FRN) indicating the deprecation of the U.S. survey foot and U.S. survey mile units from December 31, 2022.<ref name=":0" />

In the following tables in this and subsequent sections, the most common measures are shown in ''italics'', and approximate values are shown in parentheses; values not in parentheses are exact.

===International units===
{| class="wikitable"
|+List of international units
! Unit !! Name !! Divisions !! SI equivalent
|-
|{{val|1|ul=twip}}
|[[twip]]
|{{ubl|{{frac|1|20}} p|{{frac|1|1440}} in}}
| ({{val|17.6388888|ul=μm}})
|-
|{{val|1|ul=mil}}
|{{ubl|[[thousandth of an inch]]|mil}}
|{{nowrap|{{frac|1|1000}} {{val||u=in}}}}
|{{val|25.4|u=µm}}
|-
|{{val|1|u=p}}
|[[Point (typography)|point]]
| {{nowrap|{{frac|1|72}} in}}
| {{ubl|{{nowrap|{{frac|127|360}} {{val||ul=mm}}}}|({{val|352.778|ul=μm}})}}
|-
|{{val|1|u=P}}
|[[Pica (typography)|pica]]
|{{val|12|u=p}}
| {{ubl|{{nowrap|{{frac|127|30}} {{val||ul=mm}}}}|({{val|4.233|ul=mm}})}}
|-
|{{ubl|{{val|1|ul=in}}|{{val|1|u=[[inch|″]]}}}}
|''[[inch]]''
| {{val|6|u=P}}
| {{val|25.4|ul=mm}}
|-
|{{ubl|{{val|1|ul=ft}}|{{val|1|u=[[foot (length)|′]]}}}}
|''[[foot (length)|foot]]''
| {{val|12|ul=in}}
| {{val|0.3048|ul=m}}<ref name="Roberts" />
|-
|{{val|1|ul=yd}}
|''[[yard]]''
| {{val|3|ul=ft}}
| {{val|0.9144|ul=m}}
|-
|{{val|1|ul=mi}}
|''[[mile]]''
| {{ubl|{{val|5280|ul=ft}}|{{val|1760|ul=yd}}}}
| {{val|1.609344|ul=km}}
|-
|{{val|1|u=[[League (unit)|le]]}}
| ''[[League (unit)|league]]
| {{ubl|{{val|3|ul=mi}}|{{val|15840|ul=ft}}}}
| {{val|4.828032|ul=km}}
|-
|}

===International nautical units===
{| class="wikitable"
|+ List of international nautical units<ref name="Roberts"/>
! Unit !! Name !! Divisions !! SI equivalent
|-
| {{val|1|u=[[fathom|ftm]]}}
| [[fathom]]
| {{ubl|{{val|2|ul=yd}}|{{val|6|ul=ft}}}}
| {{ubl|{{nowrap|{{frac|1143|625}} {{val||ul=m}}}}|{{val|1.8288|ul=m}}}}
|-
| {{val|1|u=[[cable (unit)|cb]]}}
| [[cable (unit)|cable]]
| {{ubl|{{val|120|u=[[fathom|ftm]]}}|{{val|1.091|u=[[furlong|fur]]}}}}
| {{ubl|{{nowrap|{{frac|3429|15625}} {{val||ul=km}}}}|{{val|0.219456|u=km}}}}
|-
| {{ubl|{{val|1|ul=nmi}}|{{val|1|ul=NM}}}}
| [[nautical mile]]
| {{ubl|{{val|1.151|ul=mi}}|{{val|8.439|u=[[cable (unit)|cb]]}}}}
| {{ubl|{{val|1852|ul=m}}|{{val|1.852|ul=km}}}}
|}

===US survey units===
Note that as announced by the [[National Institute of Standards and Technology]], the US survey foot, and other units defined in terms of it, have been deprecated since 2023, "except for historic and legacy applications".<ref name=":0">{{Cite web |title=Deprecation of the United States (U.S.) Survey Foot |url=https://www.federalregister.gov/documents/2020/10/05/2020-21902/deprecation-of-the-united-states-us-survey-foot |access-date=October 19, 2023 |website=[[Federal Register]] |publication-date=October 5, 2020}}</ref><ref name=":1">{{Cite web| title = U.S. Survey Foot| work = NIST| accessdate = March 29, 2023| date = c. 2022| url = https://www.nist.gov/pml/us-surveyfoot}}</ref><ref name="NIST2023">{{Cite web| title= U.S. Survey Foot: Revised Unit Conversion Factors| work= NIST| accessdate= December 14, 2023| date = September 23, 2019| url= https://www.nist.gov/pml/us-surveyfoot/revised-unit-conversion-factors |publisher = [[National Institute of Standards and Technology]] }} Updated January 4, 2023.</ref>

{| class="wikitable"
|+ List of US Survey units
! rowspan=2|Unit !! rowspan=2|Name!! rowspan=2|Divisions!! colspan = "2" | SI equivalent
|-
!Before 2023 !! From 2023
|-
| {{val|1|u=[[link (unit)|li]]}}
| [[link (unit)|link]]
| {{ubl|{{nowrap|{{frac|33|50}} {{val||ul=ft}}}}|{{val|7.92|ul=in}}}}
| {{ubl|{{nowrap|{{frac|792|3937}} {{val||ul=m}}}}|({{val|0.20117|ul=m}})}}
| {{val|0.201168|ul=m}}
|-
| {{val|1|u=ft}}
| [[U.S. survey foot]] (deprecated since 2023)
| {{n/a}}
| {{ubl|{{nowrap|{{frac|1200|3937}} {{val||ul=m}}}}<ref name=Roberts/>| ({{val|0.3048006|u=m}})}}
| {{n/a}}
|-
| {{val|1|ul=rod}}
| {{ubl|[[rod (unit)|rod]]|"pole"|"perch"}}
| {{ubl|{{val|25|u=[[link (unit)|li]]}}|{{val|16.5|ul=ft}}}}
| {{ubl|{{nowrap|{{frac|19,800|3937}} {{val||ul=m}}}}|({{val|5.029|ul=m}})}}
| {{val|5.0292|ul=m }}
|-
| {{val|1|ul=ch}}
| [[chain (unit)|chain]]
| {{ubl|{{val|4|ul=rd}}|{{val|66|ul=ft}}}}
| {{ubl|{{nowrap|{{frac|79,200|3937}} {{val||ul=m}}}}|{{val|20.117|ul=m}}}}
| {{val|20.1168|ul=m}}
|-
| {{val|1|u=[[furlong|fur]]}}
| [[furlong]]
| {{val|10|ul=ch}}
| {{ubl|{{nowrap|{{frac|792|3937}} {{val||ul=km}}}}|({{val|201.168|ul=m}})}}
| {{val|201.168|ul=m}}
|-
| {{val|1|ul=mi}}
| {{ubl|[[U.S. survey mile]]|"statute mile"}}
| {{val|8|u=[[furlong|fur]]}}
| {{ubl|{{nowrap|{{frac|6336|3937}} {{val||ul=km}}}}<ref name="Roberts">Roberts, R.W. (February 3, 1975). ''Federal Register'' republished in Barbrow, L.E. and Judson, L. V. (1976) [https://www.govinfo.gov/content/pkg/GOVPUB-C13-691a9b38e29a85d0925f4db586b60735/pdf/GOVPUB-C13-691a9b38e29a85d0925f4db586b60735.pdf ''Weights and Measures of the United States'']. National Bureau of Standards Special Publication 447. p. 36</ref>|({{val|1.609347|ul=km}})}}
|{{val|1.609344|u=km}} (international mile)
|-
| {{val|1|u=[[league (unit)|lea]]}}
| [[league (unit)|league]]
| {{val|3|ul=mi}}
| {{ubl|{{nowrap|{{frac|19,008|3937}} {{val||ul=km}}}}<ref>Barton, John W.; Bowers, Shelby L.; Butcher, Tina G, Harshman, Richard A.; Lee, G. Diane & Warfield, Lisa, eds. [https://www.nist.gov/pml/weights-and-measures/publications/nist-handbooks/handbook-44-current-edition Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices] 2022 Edition. n.p.: National Institute of Standards and Technology. pp. B-7, C-20.</ref>| ({{val|4.828|u=km}})}}
| {{val|4.828032|ul=km}}
|}

==Area==
{| class="wikitable"
|+List of US units of area
! rowspan=2| Unit !! rowspan=2| Name !! rowspan=2| Divisions !! colspan="2" |SI equivalent
|-
!Before 2023 !! From 2023
|-
| {{ubl|{{val|1|ul=sqft}}|{{val|1|u=ft<sup>2</sup>}}}}
| square survey [[Foot (length)|foot]]
| {{val|144|ul=in2}}
| ({{val|0.09290341|ul=m2}})
| {{n/a}}
|-
| {{ubl|{{val|1|u=sq ch}}|{{val|1|u=ch<sup>2</sup>}}}}
| square [[Chain (unit)|chain]] 
| {{ubl|{{val|4356|u=sq ft (survey)}}|{{val|16|u=sq rod}}}}
| ({{val|404.6873|u=m2}})
| {{val|404.68564224|u=m2}}
|-
| {{val|1|ul=acre}}
| [[acre]]
| {{ubl|{{val|43560|u=sq ft (survey)}}|{{val|10|u=sq ch}}}} 
| ({{val|4046.873|u=m2}})
| {{val|4046.8564224|u=m2}}
|-
| {{val|1|u=[[section (United States land surveying)|section]]}}
| [[section (United States land surveying)|section]]
| {{ubl|{{val|640|ul=acre}}|{{val|1|u=sq mi (survey)}}}}
| ({{val|2.589998|u=km2}})
| {{n/a}}
|-
| {{val|1|u=twp}}
| [[survey township]] 
| {{ubl|{{val|36|u=[[section (United States land surveying)|sections]]}}|{{val|4|u=sq lea}}}} 
| ({{val|93.23993|u=km2}})
| {{n/a}}
|}

The most widely used area unit with a name unrelated to any length unit is the [[acre]]. The National Institute of Standards and Technology formerly contended that customary area units are defined in terms of the square survey foot, not the square international foot,<ref name=Roberts/> but from 2023 it states that "although historically defined using the U.S. survey foot, the statute mile can be defined using either definition of the foot, as is the case for all other units listed in this table. However, use of definitions based on the U.S. survey foot should be avoided after December 31, 2022 except for historic and legacy applications."<ref name="NIST2023"/>
{{Clear}}

==Volume==
[[File:Metric shampoo bottle.jpg|thumb|right|A {{cvt|23.7|usfloz|mL}} bottle displaying both U.S. and metric units]]
{| class="wikitable"
|+ List of US units of volume
! scope=col | Unit
! scope=col | Name
! scope=col | Divisions
! scope=col | SI equivalent
|-
| {{ubl|{{val|1|u=cu in}}|{{val|1|ul=in3}}}}
| [[cubic inch]]
| {{n/a}}
| {{val|16.387064|fmt=commas|ul=mL}}<ref>The recommended symbol for the liter in the United States is 'L' per National Institute of Standards and Technology. (1995.) ''Guide for the Use of the International System of Units (SI).'' [http://physics.nist.gov/Pubs/SP811/sec06.html#6.1.2 Special Publication 811].</ref>
|-
| {{ubl|{{val|1|fmt=commas|u=cu ft}}|{{val|1|u=ft{{sup|3}}}}}}
| [[cubic foot]]
| {{val|1728|fmt=commas|ul=cu in}}
| {{val|28.316846592|fmt=commas|ul=L}}
|-
| {{ubl|{{val|1|u=cu yd}}|{{val|1|u=yd{{sup|3}}}}}}
| [[cubic yard]]
| {{val|27|fmt=commas|ul=cu ft}}
| {{ubl|{{val|764.554857984|fmt=commas|u=L}}|{{val|0.764554857984|fmt=commas|ul=m3}}}}
|-
| {{val|1|ul=acre-foot}}
| [[acre-foot]]
| {{ubl|{{val|43560|fmt=commas|ul=cu ft}}|({{val|1613.333|fmt=commas|ul=cu yd}})}}
| {{ubl|{{val|1.23348183754752|fmt=commas|ul=ML}}|({{val|1233.482|fmt=commas|ul=m3}})}}
|}

The [[cubic inch]], [[cubic foot]] and [[cubic yard]] are commonly used for measuring volume. In addition, there is one group of units for measuring volumes of liquids (based on the [[wine gallon]] and [[Apothecaries' system#English-speaking countries|subdivisions of the fluid ounce]]), and one for measuring [[dry volume|volumes of dry material]], each with their own names and sub-units.

Although the units and their names are similar to the units in the [[imperial system]], and many units are shared between the two systems as a whole; with respect to volume, however, this is quite the contrary. The independence of the U.S. from the British Empire decades prior to the reformation of units in 1824—most notably the [[gallon]], its subdivisions, and (in mass) higher combinations above the [[pound mass|pound]]—is the cause of the differences in values.

As a non-participant in that reform, the U.S. retained the separate systems for measuring the volumes of liquids and dry material, whereas the imperial system had unified the units for both under a new imperial gallon. The U.S. uses the pre-1824 gallon ({{convert|231|in3|disp=comma}}) and Winchester bushel ({{convert|2150.42|in3|disp=comma}}), as opposed to British 1824 definition of {{convert|1|impgal}} {{=}} {{cvt|10|lb}} of water and the bushel as {{convert|8|impgal}}. 
{{Clear}}

===Fluid volume===
{| class="wikitable"
|+ List of US units of volume for liquids
! scope=col | Unit
! scope=col | Name
! scope=col | Divisions
! scope=col | Metric equivalent
|-
| {{val|1|u=[[minim (unit)|min]]}}
| [[minim (unit)|minim]]
| {{ubl|({{val|1|u=[[drop (volume)|drop]]}}) of water|({{val|0.95|u=[[Grain (unit)|grain]]}}) of water}}
| {{cvt|1/480|usfloz|μL|13|disp=out|lk=out}}
|-
| {{val|1|u=[[fluid dram|fl dr]]}}
| [[fluid dram|US fluid dram]] 
| {{val|60|u=[[minim (unit)|min]]}} 
| {{cvt|1/8|usfloz|mL|13|disp=out|lk=out}}
|-
| {{val|1|u=[[teaspoonful|tsp]]}}
| ''[[teaspoonful|teaspoon]]''
| {{val|80|u=[[minim (unit)|min]]}}
| {{cvt|1/6|usfloz|mL|11|disp=out|lk=out}}
|-
| {{val|1|u=[[tablespoon|tbsp]]}}
| ''[[tablespoon]]'' 
| {{ubl|{{val|3|u=[[teaspoonful|tsp]]}}|{{val|4|u=[[fluid dram|fl dr]]}}}} 
| {{cvt|0.5|usfloz|mL|11|disp=out|lk=out}}
|-
| {{ubl|{{val|1|u=[[US fluid ounce|floz]]}}|{{val|1|ul=usfloz}}}}
| ''[[US fluid ounce]]''
| {{ubl|{{val|2|u=[[tablespoon|tbsp]]}}|({{cvt|1|usfloz|impfloz|4|lk=out|disp=out}} of water)}}
| {{cvt|1|usfloz|mL|10|disp=out|lk=out}}
|-
| {{val|1|u=[[Shot glass#Sizes|jig]]}}
| [[Shot glass#Sizes|US shot]] 
| {{ubl|{{val|1.5|ul=usfloz}}|{{val|3|u=[[tablespoon|tbsp]]}}}} 
| {{cvt|1.5|usfloz|mL|11|disp=out|lk=out}}
|-
| {{val|1|u=[[gill (unit)|gi]]}}
| [[gill (unit)|US gill]] 
| {{ubl|2{{frac|2|3}} jig|{{val|4|ul=usfloz}}}} 
| {{cvt|4|usfloz|mL|8|disp=out|lk=out}}
|-
| {{val|1|u=[[cup (unit)|c]]}}
| ''[[cup (unit)|US cup]]''
| {{ubl|{{val|2|u=[[gill (unit)|gi]]}}|{{val|8|ul=usfloz}}}}
| {{cvt|8|usfloz|mL|7|disp=out|lk=out}}
|-
| {{ubl|{{val|1|ul=pint}}|{{val|1|ul=uspt}}}}
| ''[[Pint#US liquid pint|US pint]]'' (liquid)
| {{ubl|{{val|2|u=[[cup (unit)|c]]}}|({{cvt|1|uspt|impfloz|2|lk=out|disp=out}} of water)}}
| {{cvt|1|uspt|L|9|disp=out|lk=out}}
|-
| {{ubl|{{val|1|u=[[quart|qt]]}}|{{val|1|u=[[quart|US qt]]}}}}
| ''[[Quart#US liquid quart|US quart]]'' (liquid)
| {{val|2|ul=uspt}} 
| {{cvt|2|uspt|L|9|disp=out|lk=out}}
|-
| {{val|1|u=[[Pottle (unit)|pot]]}}
| [[Pottle (unit)|US pottle]] (liquid)
| {{val|2|u=[[quart|US qt]]}} 
| {{cvt|4|uspt|L|9|disp=out|lk=out}}
|-
| {{ubl|{{val|1|u=[[Gallon#US liquid gallon|gal]]}}|{{val|1|u=[[Gallon#US liquid gallon|US gal]]}}}}
| ''[[Gallon#US liquid gallon|US gallon]]'' (liquid)
| {{ubl|{{val|4|u=[[quart|US qt]]}}|{{val|231|ul=cu in}}}}
| {{cvt|1|usgal|L|9|disp=out|lk=out}}
|-
| {{val|1|u=[[barrel (unit)|bbl]]}}
| [[barrel (unit)|barrel]] (liquid)
| {{val|31.5|ul=usgal}}
| {{cvt|31.5|usgal|L|9|disp=out|lk=out}}
|-
| {{val|1|u=[[oil barrel|bbl]]}}
| oil barrel
| {{ubl|1{{frac|1|3}} bbl (liquid)|{{val|42|ul=usgal}}}} 
| {{cvt|42|usgal|L|9|disp=out|lk=out}}
|-
| {{val|1|ul=hogshead}}
| [[hogshead]] 
| {{ubl|{{val|2|u=[[barrel (unit)|bbl (liquid)]]}}|{{val|1.5|u=[[oil barrel|bbl (oil)]]}}|{{val|63|ul=usgal}}|{{val|8.421875|fmt=commas|ul=cu ft}}}}
| {{cvt|63|usgal|L|9|disp=out|lk=out}}
|}

One US fluid ounce is {{frac|1|16}} of a US pint, {{frac|1|32}} of a US quart, and {{frac|1|128}} of a US gallon. The teaspoon, tablespoon, and cup are defined in terms of a fluid ounce as {{frac| 1|6}}, {{frac|1|2}}, and 8 fluid ounces respectively. The fluid ounce derives its name originally from being the volume of one ounce [[avoirdupois]] of water,<ref>{{Cite web |date=2024-11-25 |title=Ounce {{!}} Imperial, Avoirdupois & Metric {{!}} Britannica |url=https://www.britannica.com/science/ounce |access-date=2024-12-01 |website=www.britannica.com |language=en}}</ref> but in the US it is defined as {{frac|1|128}} of a US gallon. Consequently, a fluid ounce of water weighs about 1.041 ounces avoirdupois.

For nutritional labeling and medicine in the US, the teaspoon and tablespoon are defined as a metric teaspoon and tablespoon{{mdash}}precisely {{val|5|u=mL}} and {{val|15|u=mL}}  respectively.<ref>21CFR101.9(b)(5)(viii) [http://edocket.access.gpo.gov/cfr_2004/aprqtr/21cfr101.9.htm 2 1CFR101.9]</ref>

The saying, "a pint's a pound the world around", refers to 16 US fluid ounces of water weighing approximately (about 4% more than) one pound avoirdupois. An imperial pint of water weighs a pound and a quarter ({{val|20|u=oz}}).

<!--[[File:20floz oz591ml.jpg|thumb|left|A {{convert|20|USoz|mL|sigfig=3|abbr=on}} bottle displaying both US and metric units.]]-->
There are varying standards for [[Barrel (unit)|barrel]] for some specific commodities, including 31 gallons for beer, 40 gallons for whiskey or kerosene, and 42 gallons for petroleum.  The general standard for liquids is 31.5 gal or half a hogshead.  The common 55-gallon size of [[drum (container)|drum]] for storing and transporting various products and wastes is sometimes confused with a barrel, though it is not a standard measure.

In the U.S., single servings of beverages are usually measured in fluid ounces. Milk is usually sold in half-pints (8 fluid ounces), pints, quarts, half gallons, and gallons. Water volume for sinks, bathtubs, ponds, swimming pools, etc., is usually stated in gallons or cubic feet.  Quantities of gases are usually given in cubic feet (at one atmosphere).

Minims, drams, gill, and pottle are rarely used currently. The gill is often referred to as a "half-cup". The ''pottle'' is often referred to as a "half-gallon".
{{Clear}}

===Dry volume===
{| class="wikitable"
|+ List of US units of volume for dry goods<ref name=HB44/>
! scope=col | Unit
! scope=col | Name
! scope=col | Divisions
! scope=col | Metric equivalent
|-
| {{val|1|u=[[Pint#US dry pint|pt]]}}
| [[Pint#US dry pint|pint]] (dry) 
| {{val|33.6003125|ul=cu in}} 
| ({{cvt|1|usdrypt|L|20|disp=out}})
|-
| {{val|1|u=[[Quart#US dry quart|qt]]}}
| [[Quart#US dry quart|quart]] (dry) 
| {{val|2|u=[[Pint#US dry pint|pt]]}}
| ({{cvt|2|usdrypt|L|20|disp=out}})
|-
| {{val|1|u=[[Gallon#US dry gallon|gal]]}}
| [[Gallon#US dry gallon|gallon]] (dry) 
| {{val|4|u=[[Quart#US dry quart|qt]]}}
| ({{cvt|8|usdrypt|L|20|disp=out}})
|-
| {{val|1|u=[[peck|pk]]}}
| [[peck]] 
| {{val|2|u=[[Gallon#US dry gallon|gal]]}}
| ({{cvt|16|usdrypt|L|20|disp=out}})
|-
| {{val|1|u=[[bushel|bu]]}}
| [[bushel]] 
| {{val|4|u=[[peck|pk]]}}
| ({{cvt|64|usdrypt|L|20|disp=out}})
|-
| {{val|1|u=[[Barrel (unit)#Dry goods in the US|bbl]]}}
| [[Barrel (unit)#Dry goods in the US|barrel]] (dry) 
| {{ubl|{{val|7056|u=cu in}}|{{val|26.25|u=[[Gallon#US dry gallon|gal]]}}|({{val|3.281|u=[[bushel|bu]]}})}}
| ({{cvt|7056|cuin|L|20|disp=out}})
|}

[[Dry volume]] is measured on a separate system, although many of the names remain the same. Small fruits and vegetables are often sold in dry pints and dry quarts. The US dry gallon is less commonly used, and was not included in the handbook that many states recognize as the authority on measurement law.<ref name="HB44">101st Conference on Weights and Measures 2016. (2017). [https://www.nist.gov/file/329706 ''Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices'']. [[National Institute of Standards and Technology]]. p. C-6, C-11, C-16.</ref><ref>[http://ts.nist.gov/WeightsAndMeasures/upload/stlaw.pdf ''Summary of State Laws and Regulations in Weights and Measures''] {{webarchive |url=https://web.archive.org/web/20111205014637/http://ts.nist.gov/WeightsAndMeasures/upload/stlaw.pdf |date=December 5, 2011 }}. (2005) [[National Institute of Standards and Technology]].</ref> However [[peck]]s, or [[bushel]]s are sometimes used—particularly for [[grape]]s, [[apple]]s and similar [[fruit]]s in agricultural regions.
{{Clear}}

==Mass and weight==
{{main|Pound (force)|Pound (mass)}}
{| class="wikitable"
|+ Conversions
! Type !! Unit !! Name !! Divisions !! SI equivalent
|-
! rowspan="8" scope="row" | Avoirdupois
| {{val|1|ul=gr}}
| [[Grain (unit)|grain]] 
| {{nowrap|{{frac|7000}} {{val||ul=lb}}}}
| {{cvt|1|gr|mg|5|disp=out|lk=out}}
|-
| {{val|1|u=[[Dram (unit)|dr]]}}
| [[Dram (unit)|dram]] 
| {{ubl|{{nowrap|{{frac|27|11|32}} {{val||ul=gr}}}}|({{val|8.859 |ul=carat}})}} 
| {{cvt|1|dram|g|9|disp=out|lk=out}}
|-
| {{val|1|ul=oz}}
| ''[[ounce]]'' 
| {{cvt|1|oz|dram|sp=us|disp=out|lk=out}} 
| {{val|28.349523125|u=g}}
|-
| {{val|1|ul=lb}}
|''[[pound (mass)|pound]]'' 
| {{cvt|1|lb|oz|disp=out|lk=out}} 
| {{cvt|1|lb|g|5|disp=out|lk=out}} 
|-
| {{ubl|{{val|1|u=[[hundredweight|cwt]]}}|{{val|1|u=[[hundredweight|US cwt]]}}}}
| US (short) [[hundredweight]]
| {{cvt|1/20|ST|lb|disp=out|lk=out}}
| {{cvt|1/20|ST|kg|6|disp=out|lk=out}}
|-
| {{ubl|{{val|1|u=[[hundredweight|cwt]]}}|{{val|1|u=[[hundredweight|long cwt]]}}}}
| long [[hundredweight]]
| {{cvt|1/20|LT|lb|0|disp=out|lk=out}}
| {{cvt|1/20|LT|kg|8|disp=out|lk=out}}
|-
| {{ubl|{{val|1|u=[[short ton|ton]]}}|{{val|1|ul=ST}}}}
| ''[[short ton]]'' 
| {{ubl|{{val|20|u=[[hundredweight|US cwt]]}}|{{cvt|1|ST|lb|0|disp=out|lk=out}}}}
| {{cvt|1|ST|kg|5|disp=out|lk=out}}
|-
| {{val|1|u=[[long ton|ton]]}}
| [[long ton]] 
| {{ubl|{{val|20|u=[[hundredweight|long cwt]]}}|{{cvt|1|LT|lb|0|disp=out|lk=out}}}}
| {{cvt|1|LT|kg|7|disp=out|lk=out}}
|-
! rowspan="4" scope="row" | Troy
| {{val|1|ul=gr}}
| [[Grain (unit)|grain]] 
| {{ubl|{{nowrap|{{frac|7000}} {{val||ul=lb}}}}|{{nowrap|{{frac|5760}} {{val||u=[[troy pound|lbt]]}}}} }}
| {{cvt|1|gr|mg|5|disp=out|lk=out}}
|-
| {{val|1|ul=dwt}}
| [[pennyweight]] 
| {{ubl|{{val|24|ul=gr}}|({{val|7.776|ul=carat}})}}
| {{cvt|24|gr|g|8|disp=out|lk=out}}
|-
| {{val|1|ul=ozt}}
| [[troy ounce]] 
| {{val|20|ul=dwt}}
| {{cvt|1|ozt|g|7|disp=out|lk=out}}
|-
| {{val|1|u=[[troy pound|lbt]]}}
| [[troy pound]] 
| {{ubl|{{cvt|1|lbt|ozt|disp=out|lk=out}}|({{cvt|1|lbt|oz|disp=out|8|lk=out}})}}
| {{cvt|1|lbt|g|7|disp=out|lk=out}}
|}

There have historically been five different English systems of mass: [[Pound (mass)#Tower pound|tower]], [[apothecaries' system|apothecaries']], [[troy weight|troy]], [[avoirdupois system|avoirdupois]], and [[metric system|metric]]. Of these, the avoirdupois weight is the most common system used in the U.S., although Troy weight is still used to weigh precious metals. Apothecaries' weight—once used by pharmacies—has been largely replaced by metric measurements. Tower weight fell out of use in England (due to legal prohibition in 1527) centuries ago, and was never used in the U.S. The [[imperial units|imperial]] system, which is still used for some measures in the United Kingdom and other countries, is based on avoirdupois, with variations from U.S. customary units larger than a pound.

The pound avoirdupois, which forms the basis of the U.S. customary system of mass, is defined as exactly {{convert|1|lb|g|5|disp=out|lk=out|abbr=off}} by agreement between the U.S., the United Kingdom, and other English-speaking countries in 1959. Other units of mass are defined in terms of it.

The avoirdupois pound is legally defined as a measure of [[mass]],<ref>[http://ts.nist.gov/WeightsAndMeasures/Publications/upload/AppendC-09-HB44-FINAL.pdf NIST Handbook 44, Appendix C, ''General Tables of Units of Measurement'', page C-6 ''Avoirdupois Units of Mass''] {{webarchive|url=https://web.archive.org/web/20111018070228/http://ts.nist.gov/WeightsAndMeasures/Publications/upload/AppendC-09-HB44-FINAL.pdf |date=October 18, 2011 }}</ref> but the name pound is also applied to measures of [[Force (physics)|force]]. For instance, in many contexts, the [[Pound (mass)|pound]] avoirdupois is used as a unit of mass, but in some contexts, the term "pound" is used to refer to "[[pound-force]]". The [[slug (unit)|slug]] is another unit of mass derived from pound-force.

Troy weight, avoirdupois weight, and apothecaries' weight are all built from the same basic unit, the grain, which is the same in all three systems. However, while each system has some overlap in the names of their units of measure (all have ounces and pounds), the relationship between the grain and these other units within each system varies. For example, in apothecary and troy weight, the pound and ounce are the same, but are different from the pound and ounce in avoirdupois in terms of their relationships to grains and to each other. The systems also have different units between the grain and ounce (apothecaries' has scruple and [[dram (unit)|dram]], troy has [[pennyweight]], and avoirdupois has just dram, sometimes spelled ''drachm'').  The dram in avoirdupois weighs just under half of the dram in apothecaries'. The [[fluid dram]] unit of volume is based on the weight of 1 dram of water in the apothecaries' system.

To alleviate confusion, it is typical when publishing non-avoirdupois weights to mention the name of the system along with the unit. Precious metals, for example, are often weighed in "troy ounces", because just "ounce" would be more likely to be assumed to mean an avoirdupois ounce.

For the pound and smaller units, the U.S. customary system and the British imperial system are identical. However, they differ when dealing with units larger than the pound. The definition of the pound avoirdupois in the imperial system is identical to that in the U.S. customary system.

In the U.S., only the ounce, pound and short ton{{snd}} known in the country simply as the ton{{snd}} are commonly used, though the hundredweight is still used in agriculture and shipping. The grain is used to describe the mass of propellant and projectiles in small arms [[ammunition]]. It was also used to measure medicine and other very small masses.

===Grain measures===
In agricultural practice, a [[bushel]] is a fixed volume of {{convert|2150.42|in3|L|abbr=off|sp=us}}. The mass of grain will therefore vary according to density. Some nominal weight examples are:<ref>{{Cite web|title=United States Department of Agriculture|url=https://www.ers.usda.gov/data-products/feed-grains-database/documentation/|date=August 20, 2019|website=United States Department of Agriculture|access-date=May 28, 2020}}</ref><ref>{{Cite web|title=Weights and Measures of agricultural commodities|url=https://www.nass.usda.gov/Statistics_by_State/Delaware/Publications/Annual_Statistical_Bulletin/2009/Page29.pdf|website=United States Department of Agriculture-National Agricultural Statistics Service|access-date=May 28, 2020}}</ref>
* 1 bushel (corn) = {{cvt|56|lb|kg|4}}
* 1 bushel (wheat) = {{cvt|60|lb|kg|4}}
* 1 bushel (barley) = {{cvt|48|lb|kg|4}}
{{Clear}}

==Cooking measures==
{{main|Cooking weights and measures}}
{| class="wikitable" style="text-align: right" 
|+ Common volume measures in English-speaking countries{{smalldiv|(Comparable measures listed for comparison purposes.)}}
!| Measure
! [[Australia]] !! [[Canada]] !! [[UK]] !! [[United States|US]] || US [[Food and Drug Administration|FDA]]<ref name="CFR21_2_101_9">{{cite web |url=http://www.gpo.gov/fdsys/pkg/CFR-2012-title21-vol2/pdf/CFR-2012-title21-vol2-sec101-9.pdf |title=Title 21, 101.9 Nutrition labeling of food |work=Code of Federal Regulations |publisher=[[US Government Printing Office]] |date=April 12, 2012 |access-date=November 2, 2014 |quote=For nutrition labeling purposes, a teaspoon means 5 milliliters (mL), a tablespoon means 15&nbsp;mL, a cup means 240&nbsp;mL, 1 fl oz means 30&nbsp;mL, and 1&nbsp;oz in weight means 28&nbsp;g.}}</ref>
|-
| align=left | [[Teaspoon]] || {{val|5|ul=mL}} ||{{val|5|ul=mL}} || {{val|5|ul=mL}} || {{cvt|1/6|usfloz|mL|2|disp=out|lk=out}} || {{val|5|ul=mL}}
|-
| align=left | [[Dessertspoon]] || {{val|10|ul=mL}} || {{n/a}} || {{val|10|ul=mL}} || {{n/a}} || {{n/a}}
|-
| align=left | [[Tablespoon]] || {{val|20|ul=mL}} || {{val|15|ul=mL}} || {{val|15|ul=mL}} || {{cvt|3/6|usfloz|mL|2|disp=out|lk=out}} || {{val|15|ul=mL}}
|-
| align=left | [[Fluid ounce]] || {{n/a}} || {{n/a}} || {{cvt|1|impfloz|mL|2|disp=out|lk=out}} || {{cvt|1|usfloz|mL|2|disp=out|lk=out}} || {{val|30|ul=mL}}
|-
| align=left | [[Cup (volume)|Cup]] || {{val|250|ul=mL}} || {{val|250|ul=mL}} || {{n/a}} || {{cvt|8|usfloz|mL|2|disp=out|lk=out}} || {{val|240|ul=mL}}
|-
| align=left | [[Pint]] || {{val|570|ul=mL}} || {{n/a}} || {{cvt|1|imppt|mL|2|disp=out|lk=out}} || {{cvt|1|uspt|mL|2|disp=out|lk=out}} || {{n/a}}
|-
| align=left | [[Quart]] || {{n/a}} || {{n/a}} || {{cvt|0.25|impgal|L|2|disp=out|lk=out}} || {{cvt|2|uspt|L|2|disp=out|lk=out}} || {{n/a}}
|-
| align=left | [[Gallon]] || {{n/a}} || {{n/a}} || {{cvt|1|impgal|L|2|disp=out|lk=out}}  || {{cvt|1|usgal|L|2|disp=out|lk=out}}  || {{n/a}}
|}

The most common practical cooking measures for both liquid and dry ingredients in the U.S. are ''teaspoon'', ''tablespoon'', and ''cup'', along with halves, thirds, quarters, and eighths of each.  Units used are ''pounds'', ''ounces'', and ''fluid ounces''. Common sizes are also used, such as ''can'' (presumed size varies depending on product), ''jar'', ''square'' (e.g. of chocolate), ''stick'' (e.g. of butter), or portion of fruit or vegetable (e.g. a half lemon, two medium onions).<ref>{{Cite book |last=Graham |first=Eunice |chapter=Common Measurements with Factor Labeling |chapter-url=https://openwa.pressbooks.pub/culinarymath/chapter/common-measurements-with-factor-labeling/ |title=Culinary Math |publisher=Open Washington Pressbooks |language=en}}</ref>
{{Clear}}

==Temperature==
Degrees [[Fahrenheit]] are used in the U.S. to measure [[temperature]]s in most non-scientific contexts. The [[Rankine scale]] of [[absolute temperature]] also saw some use in [[thermodynamics]]. Scientists worldwide use the [[kelvin]] and [[degree Celsius]]. Several U.S. technical standards are expressed in Fahrenheit temperatures, and some American medical practitioners use degrees Fahrenheit for body temperature.

The relationship between the different temperature scales is [[linear function|linear]] but the scales have different zero points, so conversion is not simply multiplication by a factor. Pure water freezes at {{nowrap|1=32 °F = 0 °C}} and boils at {{nowrap|1=212 °F = 100 °C}} at 1 [[Atmosphere (unit)|atm]].  The conversion formula is:
<math display=block>\{T\}_\mathrm{^\circ F} = \tfrac{9}{5} \{T\}_\mathrm{^\circ C} + 32</math>

or inversely as
<math display=block>\{T\}_\mathrm{^\circ C} = \tfrac{5}{9}\bigl(\{T\}_\mathrm{^\circ F} - 32\bigr).</math>
{{Clear}}

==Other units==
Length
* 1 [[hand (unit)|hand]] = 4 in = {{cvt|4.000|in|disp=out}}
* 1 U ([[rack unit]]) = 1.75 in = {{cvt|1.7500|in|disp=out}}
Volume
* 1 [[board-foot]] = 1&nbsp;ft × 1&nbsp;ft × 1 in = {{cvt|144.0|in3|dm3|disp=out|lk=on}}
Mass
* 1 [[slug (unit)|slug]] = 1 [[pound-force|lbf]]⋅s<sup>2</sup>/ft ≈ 14.59390&nbsp;kg
Force
* 1 [[poundal (unit)|poundal]] = force to accelerate 1 pound mass 1 foot/second/second ≈ {{convert|1|pdl|N|3|disp=out|lk=on|abbr=off}}.
* 1 [[kip (unit)|kip]] = 1000&nbsp;lbf ≈ {{cvt|1000.000|lbf|kN|disp=out|lk=on}}
Energy
* 1 [[foot-pound (energy)|foot-pound]] ≈ {{cvt|1.000|ft.lbf|J|disp=out}} 
* 1 [[British thermal unit]] (Btu) ≈ {{cvt|1.000|Btu|kJ|disp=out}} (1,054–1,060 J, depending on which of several definitions of BTU is used)
* 1 [[Quad (unit)|Quad]] 10<sup>15</sup> BTU, one quadrillion BTU (short-scale) or 1.055×10<sup>18</sup> joule (1.055 exajoules or EJ)
Power
* 1 [[horsepower]] ≈ {{cvt|1.0000|hp|W|disp=out|lk=on}}
* 1 [[ton of refrigeration]] (12,000 Btu/h) = {{cvt|12000.|Btu/h|kW|disp=out}}
Pressure
* 1 [[inch of mercury]] = the pressure produced by 1 inch height of mercury = {{convert|1|inHg|Pa|2|disp=out|abbr=off}} (33.8639 hPa, millibars)
* 1 [[pound per square inch]] (psi) ≈ {{cvt|1.0000|psi|Pa|disp=out}}
Torque
* 1 [[pound-foot (torque)|pound-foot]] ≈ {{cvt|1.000|lbf.ft|N.m|disp=out|lk=on}}
Insulation
* 1 [[R-value (insulation)|''R''-value]] (ft<sup>2</sup>⋅°F⋅h/Btu) ≈ 0.1761 ''R''<sub>SI</sub> (K⋅m<sup>2</sup>/W)

Various combination units are in common use; these are straightforwardly defined based on the above basic units.

Sizing systems are used for various items in commerce, several of which are U.S.-specific:
* [[US standard clothing size]]
* [[American wire gauge]] is used for most metal wire.
* [[Scoop (utensil)]] sizes, numbered by scoops per quart
* Thickness of [[leather]] is measured in ounces, 1&nbsp;oz equals {{convert|1/64|in}}.<ref>{{cite book|last1=Wells|first1=Larry J.|title=Makin' Leather: A Manual of Primitive and Modern Leather Skills|date=1981|publisher=Cedar Fort|isbn=0882908359|page=13}}</ref>
* Bolts and screws follow the [[Unified Thread Standard]] rather than the [[ISO metric screw thread]] standard.
* [[Knitting needles]] in the United States are measured according to a [[Knitting needle#Needle sizes and conversions|non-linear unitless numerical system]].
* Thickness of [[aluminum foil]] is measured in ''mils'' ({{frac|1000}} inch, or 0.0254&nbsp;mm) in the United States.
* Cross-sectional area of electrical wire is measured in [[circular mil]]s in the U.S. and Canada, one circular mil (cmil) being equal to {{val|5.067|e=−4|u=mm2}} (or {{val|7.854|e=−7|u=in2}}). Since this is so small, actual wire is commonly measured in thousands of a cmil, called either kcmil or MCM.
* The ''mil'' or ''thou'' is also sometimes used to mean [[thousandth of an inch]].
* [[Sheet metal]] in the U.S. is commonly measured in [[Sheet metal#Gauge|gauge]] (not to be confused with the American wire gauge), which is derived from weight and thus differs by material.
* [[Nominal Pipe Size]] is used for the outside diameter of pipes. Below NPS14, the NPS number is not consistent with the pipe diameter in inches.
* [[Copper tubing]], however, is measured in [[Copper tubing#United States|nominal size]], {{frac|8}} inch less than the outside diameter.
* The [[Nominal Pipe Size#NPS tables for selected sizes|Schedule]] system is used for standard pipe thicknesses.
* Alcohol content is frequently given in [[Alcohol proof|proof]], 2 × percent [[alcohol by volume]]
* The [[Cord (unit)|cord]] is used for volume of firewood.
* The [[Square (unit)|square]] is used to mean 100 square feet in construction.
* [[Heat flux]] in the U.S. is measured in [[Langley (unit)|langleys]].

==Other names for U.S. customary units==
The United States Code refers to these units as "traditional systems of weights and measures".<ref>{{usc|15|205b}}</ref>

Other common ways{{fact|date=February 2024}} of referring to the system are: ''customary'', ''standard'', ''English'', or ''imperial'' (which refers to the post-1824 reform measures used throughout the British Empire & Commonwealth countries).<ref>{{Cite web| last = Kelechava| first = Brad| title = US Customary System: An Origin Story| work = The ANSI Blog| access-date = February 25, 2024| date = June 18, 2018| url = https://blog.ansi.org/2018/06/us-customary-system-history-units/}}</ref> Another term is the [[foot–pound–second system|foot–pound–second]] (FPS) system, as opposed to [[centimetre–gram–second system of units|centimeter–gram–second]] (CGS) and [[MKS system of units|meter–kilogram–second]] (MKS) systems.

Tools and fasteners with sizes measured in inches are sometimes called "SAE bolts" or "SAE wrenches" to differentiate them from their metric counterparts.  The [[SAE International|Society of Automotive Engineers]] (SAE) originally developed fasteners standards using U.S. units for the U.S. auto industry; the organization now uses metric units.<ref>{{cite web |url= http://www.sae.org/exdomains/standardsdev/global_resources/SAE%20Metric%20Users%20Guide.pdf |title= Rules for SAE Use of SI (Metric) Units |date= May 1999 |publisher= Society of Automotive Engineers, Inc |access-date=July 1, 2012}}</ref>

==See also==
* [[Board foot]]
* [[Conversion of units]]
* [[History of measurement]] and [[units of measurement]]
* [[Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States]] (1790)
* [[Mars Climate Orbiter#Cause of failure|''Mars Climate Orbiter'']], which failed due to a measurement-units-related software bug
* [[Standard cubic foot]]

==References==
{{Reflist}}

==External links==
* [https://web.archive.org/web/20080316180643/http://www.unc.edu/~rowlett/units/index.html Rowlett's Dictionary of Units of Measurement (archived)]

{{United States Customary Units|state=expanded}}
{{systems of measurement|sp=us}}
{{Authority control}}
{{DEFAULTSORT:United States Customary Units}}
[[Category:Customary units of measurement in the United States| ]]
[[Category:Systems of units]]