ounce#International troy ounce

Ounce derives from the Ancient Roman {{lang|la|uncia}} (meaning: a twelfth), a unit in the Ancient Roman units of measurement weighing about 27.4 grams or 96.7% of an avoirdupois ounce,{{cite encyclopedia | title=Measurement system |author=Ronald Zupko |url=https://www.britannica.com/science/measurement-system#ref360981 |encyclopedia=Encyclopedia Britannica }} that was one-twelfth ({{frac|1|12}}) of the Roman pound ({{lang|la|libra}}).{{L&S|uncia|ref}} This in turn comes from Latin {{lang|la|unus}} ('one'), and thus originally meant simply 'unit'. The term uncia was borrowed twice: first into Pre–Old English, becoming {{lang|ang|ynce}} in Old English, which survives in modern English as inch;{{OED|inch}} and a second time into Middle English through Anglo-Norman and Middle French ({{lang|enm|unce, once, ounce}}), yielding English ounce.{{OED|ounce}} The abbreviation oz came later from the Italian cognate {{lang|it|onza}}, pronounced {{IPA|it|ˈontsa|}} (or later {{lang|it|oncia}}, pronounced {{IPA|it|ˈontʃa|}}).

Historically, in different parts of the world, at different points in time, and for different applications, the ounce (or its translation) has referred to broadly similar but still slightly different standards of mass.

The international avoirdupois ounce (abbreviated oz) is defined as exactly 28.349523125 g under the international yard and pound agreement of 1959, signed by the United States and countries of the Commonwealth of Nations.

In the avoirdupois system, sixteen ounces make up an avoirdupois pound, and the avoirdupois pound is defined as 7000 grains; one avoirdupois ounce is therefore equal to 437.5 grains.

The ounce is still a standard unit in the United States. In the United Kingdom it ceased to be an independent unit of measure in 2000,{{cite web |url=http://www.opsi.gov.uk/si/si1995/Uksi_19951804_en_1.htm |title=The Units of Measurement Regulations 1995 (Article 3) |date=20 September 2000 |access-date=4 October 2022 |quote=the provision shall, unless the context otherwise requires, be construed on or after that date as if the indication of quantity concerned were expressed in the corresponding metric unit.}} but may still be seen as a general indicator of portion sizes in burger and steak restaurants.

{{Main|Troy ounce}}

A troy ounce (abbreviated oz t) is equal to 480 grains. Consequently, the international troy ounce is equal to exactly 31.1034768 grams. There are 12 troy ounces in the obsolete troy pound.

The troy ounce is used only to express the mass of precious metals such as gold, platinum, palladium, rhodium or silver. Bullion coins are the most common products marketed in troy ounces, but precious metal bars also exist in gram and kilogram (kg) sizes. (A kilogram bullion bar contains {{convert|1|kg|ozt|sigfig=5|disp=out|abbr=off}}.)

For historical measurement of gold,

• a fine ounce is a troy ounce of pure gold content in a gold bar, computed as fineness multiplied by gross weight{{cite web|last=London Bullion Market Association|title=Market Basics|url=http://www.lbma.org.uk/pages/index.cfm?page_id=17|url-status=dead|archive-url=https://web.archive.org/web/20120308170239/http://www.lbma.org.uk/pages/index.cfm?page_id=17|archive-date=8 March 2012}}
• a standard ounce is a troy ounce of 22 carat gold, 91.66% pure (an 11 to 1 proportion of gold to alloy material)

Some countries have redefined their ounces in the metric system.{{cite book |first1=D. A. |last1=Wittop Koning |first2=G. M. M. |last2=Houben |title=2000 jaar gewichten in de nederlanden|language=nl |publisher=De Tijdstroom |location=Lochem-Poperinge |year=1980 |isbn=9060879651 }} {{in lang|nl}} For example, the German apothecaries' ounce of 30 grams is very close to the previously widespread Nuremberg ounce, but the divisions and multiples come out in metric.

In 1820, the Dutch redefined their ounce (in Dutch, ons) as 100 grams. In 1937 the IJkwet of the Netherlands officially abolished the term, but it is still commonly used.{{cite web|url=http://www.outpostthehague.com/relocations/insideguide/wheretoturn.htm |title=Guide to The Hague – Where to turn |access-date=1 January 2008 |archive-url=https://web.archive.org/web/20080316071124/http://www.outpostthehague.com/relocations/insideguide/wheretoturn.htm |archive-date=16 March 2008 |url-status=dead }}:nl:Nederlands metriek stelsel

Dutch amendments to the metric system, such as an ons or 100 grams, has been inherited, adopted, and taught in Indonesia beginning in elementary school. It is also listed as standard usage in Indonesia's national dictionary, the Kamus Besar Bahasa Indonesia, and the government's official elementary-school curriculum.{{Cite web |url=https://kbbi.kemdikbud.go.id/entri/ons |title=Ons in KBBI |access-date=12 July 2019 |archive-date=12 July 2019 |archive-url=https://web.archive.org/web/20190712173704/https://kbbi.kemdikbud.go.id/entri/ons |url-status=live }}

The apothecaries' ounce (abbreviated ℥) equivalent to the troy ounce, was formerly used by apothecaries, and is thus obsolete.

"Maria Theresa ounce" was once introduced in Ethiopia and some European countries, which was equal to the weight of one Maria Theresa thaler, or 28.0668 g.{{Cite book

| last = Greenfield

| first = Richard

| year = 1965

| title = Ethiopia: a new political history

| publisher = F. A. Praeger

| page = 327

| url= https://books.google.com/books?id=T2MFAAAAIAAJ&q=%22Maria+theresa+ounce%22

}}{{Cite book

| year = 1962

| title = Ethiopia observer

| volume = 6

| pages = 187–8

| url= https://books.google.com/books?id=EfvRAAAAMAAJ&q=%22Maria+theresa+ounce%22

}} Both the weight and the value are the definition of one birr, still in use in present-day Ethiopia and formerly in Eritrea.{{Citation needed|date=December 2007}}

{{Further|Spanish customary units}}

The Spanish pound ({{langx|es|libra}}) was 460 g.Diccionario de la Real Academia Española, 23rd edition, [http://buscon.rae.es/draeI/SrvltObtenerHtml?IDLEMA=45615&NEDIC=Si libra] {{Webarchive|url=https://web.archive.org/web/20110720145109/http://buscon.rae.es/draeI/SrvltObtenerHtml?IDLEMA=45615&NEDIC=Si |date=20 July 2011 }} The Spanish ounce (Spanish {{lang|es|onza}}) was {{frac|1|16}} of a pound, i.e. 28.75 g.Diccionario de la Real Academia Española, 23rd edition, [http://buscon.rae.es/draeI/SrvltObtenerHtml?IDLEMA=82285&NEDIC=Si onza] {{Webarchive|url=https://web.archive.org/web/20110720145123/http://buscon.rae.es/draeI/SrvltObtenerHtml?IDLEMA=82285&NEDIC=Si |date=20 July 2011 }} It was further subdivided into 16 {{lang|es|adarmes}} (each 1.8 grams). For pharmaceutical use, the Greek {{lang|es|dracma}} was used, subdividing the Spanish ounce into 8 (3.6 grams), due to being equivalent to {{frac|1|12}} of an avoirdupois ounce. In either case, it could be further subdivided into grains, each one 49.9 milligrams.

==== Tower ounce ====

The Tower ounce of {{convert|450|gr|g|abbr=off}} was a fraction of the tower pound used in the English mints, the principal one being in the Tower of London. It dates back to the Anglo-Saxon coinage weight standard. It was abolished in favour of the Troy ounce by Henry VIII in 1527.{{cite book |first=Robert |last=Slater |title=An Inquiry into the Principles involved in the Decimalization of the Weights, Measures, and Monies of the United Kingdom |location=London |publisher=Arthur Hall |date=1855 |page=11 |url=https://books.google.com/books?id=nctVAAAAcAAJ&pg=PA11}}

{{Main|Pound-force}}

An ounce-force is {{frac|16}} of a pound-force, or about {{convert|1/16|lbf|N|7|abbr=off|lk=out|disp=output only}}. It is defined as the force exerted by a mass of one avoirdupois ounce under standard gravity (at the surface of the earth, its weight).

The "ounce" in "ounce-force" is equivalent to an avoirdupois ounce; ounce-force is a measurement of force using avoirdupois ounces. It is customarily not identified or differentiated. The term has limited use in engineering calculations to simplify unit conversions between mass, force, and acceleration systems of calculations.

{{Main|Fluid ounce}}

A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl.) is a unit of volume. An imperial fluid ounce is defined in British law as exactly 28.4130625 millilitres,{{cite web | title=The Units of Measurement Regulations 1995 {{!}} RELEVANT IMPERIAL UNITS, CORRESPONDING METRIC UNITS AND METRIC EQUIVALENTS |url=https://www.legislation.gov.uk/uksi/1995/1804/schedule/made |publisher=Government of the United Kingdom |date=1995 |access-date=4 October 2022}} while a US customary fluid ounce is exactly 29.5735295625 mL,{{cite web |title= Handbook 44 – 2018 {{!}} Appendix C. General Tables of Units of Measurement |page=C-15 |url=https://www.nist.gov/system/files/documents/2017/12/07/appc-18-hb44-final.pdf |date=2017 |access-date=4 October 2022 |publisher=NIST}} and a US food labelling fluid ounce is 30 mL.{{cite web |title=Guidance for Industry: Guidelines for Determining Metric Equivalents of Household Measures |url=https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-industry-guidelines-determining-metric-equivalents-household-measures |archive-url=https://web.archive.org/web/20190701142046/https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-industry-guidelines-determining-metric-equivalents-household-measures |url-status=dead |archive-date=1 July 2019 |date=October 1993 |access-date=4 October 2022 |publisher=Food and Drugs Administration}} The fluid ounce is sometimes referred to simply as an "ounce" in contexts where its use is implicit, such as bartending.

Ounces are also used to express the "weight", or more accurately the areal density, of a textile fabric in North America, Asia, or the UK, as in "16 oz denim". The number refers to the weight in ounces of a given amount of fabric, either a yard of a given width, or a square yard, where the depth of the fabric is a fabric-specific constant.{{cite web |url=http://www.fashiondex.com/howtos/htstfm4.php|title=How to shop the fabric market |access-date=10 December 2008 }}

The most common unit of measure for the copper thickness on a printed circuit board (PCB) is ounces (oz), as in mass. It is the resulting thickness when the mass of copper is pressed flat and spread evenly over a one-square-foot area. 1 oz will roughly equal 34.7 μm.{{cite web |url=http://www.pcbuniverse.com/pcbu-tech-tips.php?a=4|access-date=13 November 2016 |title=Copper Thickness FAQ}}

{{Reflist}}

• [https://web.archive.org/web/20180818124536/http://www.unc.edu/~rowlett/units/dictO.html#ounce Dictionary of Units: Ounce]

{{Imperial units}}

{{United States Customary Units}}

{{Authority control}}

Category:Customary units of measurement in the United States

Category:Imperial units

Category:Units of mass