The ounce (abbreviated oz; apothecary symbol: ?) is a unit of mass, weight, or volume used in most British derived customary systems of measurement. The common avoirdupois ounce (approximately 28.3 g) is of a common avoirdupois pound; this is the United States customary and British imperial ounce. It is primarily used in the United States to measure packaged foods and food portions, postal items, areal density of fabric and paper, boxing gloves, and so on; but sometimes also elsewhere in the Anglosphere.
Besides the common ounce, several other ounces are in current use:
Historically, a variety of different ounces measuring mass or volume were used in different jurisdictions by different trades.
Ounce derives from Latin uncia, a unit that was one-twelfth () of the Roman pound (libra). Ounce was borrowed twice: first into Old English as ynsan or yndsan from an unattested Vulgar Latin form with ts for c before i (palatalization) and second into Middle English through Anglo-Norman and Middle French (unce, once, ounce). The abbreviation oz came later from the cognate Italian word onza (now spelled oncia).
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 different standards of mass.
|International avoirdupois ounce||28.349523125||437.5|
|International troy ounce||31.1034768||480|
|Maria Theresa ounce||28.0668|
|Spanish ounce (onza)||28.75|
|French ounce (once)||30.59|
|Portuguese ounce (onça)||28.69|
|Roman/Italian ounce (oncia)||27.4|
|Dutch metric ounce (ons)||100|
|Dutch (pre-metric) ounce (ons)||30|
|Chinese metric ounce ()||50|
|English Tower Ounce||29.16||450|
The international avoirdupois ounce 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.
The ounce is still a standard unit in the United States. In the United Kingdom it ceased to be a legal unit of measure in 2000, but is still in general usage on an informal basis. In addition it is the normal measure for portion sizes in British restaurants.
Today, 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 produced and marketed in troy ounces, but precious metal bars also exist in gram and kilogram (kg) sizes. (A kilogram bullion bar contains 32.15074657 troy ounces.)
For historical measurement of gold,
Some countries have redefined their ounces in the metric system. 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. 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.
"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. Both the weight and the value are the definition of one birr, still in use in present-day Ethiopia and formerly in Eritrea.
The Tower ounce of 450 grains was 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.
An ounce-force is of a pound-force, or 0.2780139 newtons.
The "ounce" in "ounce-force" is equivalent to an avoirdupois ounce; ounce-force is a measurement of force using avoirdupois ounces. However, it is not necessary to identify it as such or to differentiate it in that way because there is no equivalent measure of force using troy or any other "ounce".
A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl.) is a unit of volume equal to about 28.4 ml in the imperial system or about 29.6 ml in the US system. The fluid ounce is sometimes referred to simply as an "ounce" in applications 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.
|Fabric type||Typical weight in ounces|
|Organza, voile, chiffon||1-3|
|Most cottons, wools, silks, muslin, linen||4-7|
|Denim, corduroy, twill, velvet||7-16|
The most common unit of measure for the copper thickness on a printed circuit board (PCB) is ounces (oz). It is the resulting thickness when 1 oz of copper is pressed flat and spread evenly over a one-square-foot area. This roughly equals 34.7 µm.