Currently in use
International avoirdupois ounce
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.
In the
avoirdupois system, sixteen ounces make up a
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, but in the
United Kingdom it is now only used informally, having ceased to be a legal unit of measure in 2000.
[3]
International troy ounce
Main article:
Troy ounce
A
troy ounce is equal to 480
grains. Consequently, the
international troy ounce is equal to exactly 31.1034768 grams. There are 12 troy ounces in the now obsolete
troy pound.
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,
- a fine ounce is a troy ounce of pure gold content in a gold bar, computed as fineness multiplied by gross weight[4]
- a standard ounce is a troy ounce of 22 carat gold, 91.66% pure (an 11 to 1 proportion of gold to alloy material)
Metric ounces
Some countries have redefined their ounces in the
metric system.
[5] 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.
[6][7] 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.
[8]
Historical
Apothecaries' ounce
The obsolete
apothecaries' ounce (abbreviated ℥) equivalent to the troy ounce, was formerly used by
apothecaries.
Maria Theresa ounce
"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.
[9][10] 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]
Spanish ounce
Further information:
Spanish customary units
The Spanish pound (
Spanish libra) was 460 g.
[11] The Spanish ounce (Spanish
onza) was
1⁄
16 of a pound, i.e. 28.75 g.
[12]
Tower ounce
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.