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This article is about the unit of mass. For the unit of force, see Pound-force
Pound-force

The pound-force or simply pound is a Units of measurement of force....
. For the unit of volume, see Fluid ounce
Fluid ounce

A fluid ounce is a unit of volume in both the Imperial unit and the United States customary units systems. It is common to refer to the unit simply as an ounce, especially in cases where no confusion with the unit of mass is likely to occur....
. For all other uses, see Ounce (disambiguation)
Ounce (disambiguation)

An ounce can be:* ounce, the name of a number of units of mass;* the ounce-force, a unit of force, 1⁄16 of the pound-force;...
. The ounce (abbreviated: oz, the old Italian word onza, now spelled oncia; apothecary
Apothecary

Apothecary is a historical name for a medicine who formulates and dispenses materia medica to physicians, surgery and patients ? a role now served by a pharmacist ....
 symbol: ?) is a unit
Units of measurement

The definition, agreement and practical use of units of measurement have played a crucial role in human endeavour from early ages up to this day....
 of mass
Mass

In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force....
 in a number of different systems, including various systems of mass that form part of the imperial
Imperial unit

Imperial units or the imperial system is a system of units, first defined in the British Weights and Measures Act of 1824, later refined and reduced....
 and United States customary
United States customary units

The United States Customary System for units of measurement, also known in the United States as English, Imperial or standard units, is the primary and most commonly-used system of units of measurement in the United States....
 systems. Its size can vary from system to system.






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This article is about the unit of mass. For the unit of force, see Pound-force
Pound-force

The pound-force or simply pound is a Units of measurement of force....
. For the unit of volume, see Fluid ounce
Fluid ounce

A fluid ounce is a unit of volume in both the Imperial unit and the United States customary units systems. It is common to refer to the unit simply as an ounce, especially in cases where no confusion with the unit of mass is likely to occur....
. For all other uses, see Ounce (disambiguation)
Ounce (disambiguation)

An ounce can be:* ounce, the name of a number of units of mass;* the ounce-force, a unit of force, 1⁄16 of the pound-force;...
. The ounce (abbreviated: oz, the old Italian word onza, now spelled oncia; apothecary
Apothecary

Apothecary is a historical name for a medicine who formulates and dispenses materia medica to physicians, surgery and patients ? a role now served by a pharmacist ....
 symbol: ?) is a unit
Units of measurement

The definition, agreement and practical use of units of measurement have played a crucial role in human endeavour from early ages up to this day....
 of mass
Mass

In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force....
 in a number of different systems, including various systems of mass that form part of the imperial
Imperial unit

Imperial units or the imperial system is a system of units, first defined in the British Weights and Measures Act of 1824, later refined and reduced....
 and United States customary
United States customary units

The United States Customary System for units of measurement, also known in the United States as English, Imperial or standard units, is the primary and most commonly-used system of units of measurement in the United States....
 systems. Its size can vary from system to system. The most commonly used ounces today are the international avoirdupois ounce and the international troy ounce.

Definitions

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 (or weight, before the distinction between weight and mass
Mass versus weight

In the Physics, mass and weight are different properties. Mass is an inertial property; that is, the tendency of an object to remain at constant velocity unless acted upon by an external force....
 developed). An ounce is more often a measure of force as opposed to mass or weight, comparable to lbf, or pound force. Some of these other ounces are described below.

 Summary of ounce units
ounce variant mass in gram
Gram

The gram , ; symbol g, is a Physical unit of mass.Originally defined as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre, and at the temperature of melting ice" , a gram is now defined as one one-thousandth of the SI base unit, the kilogram, or Scientific notation kg, which itself is...
s		 mass in grain
Grain (measure)

In many cultures, a grain is a Physical unit of measurement of mass that is based upon the mass of a single seed of a typical cereal. Historically, in Europe, the average masses of wheat and barley grain were used to define units of mass....
s
International avoirdupois ounce28.35437.5
International troy ounce31.1034768480
Apothecaries' ounce
Maria Theresa ounce
Dutch metric ounce
Chinese metric ounce
Note: The grain values for the Maria Theresa, Dutch and Chinese
ounces are rounded to the nearest thousandth of a grain.


International avoirdupois ounce

The avoirdupois
Avoirdupois

The avoirdupois system is a system of Units of measurement based on a pound of sixteen ounces. It is the everyday system of weight used in the United States....
 ounce is the most commonly used ounce today. It is defined to be one sixteenth of an avoirdupois pound
Pound (mass)

The pound or pound-mass is a Units of measurement of massused in the Imperial unit, United States customary units and other systems of measurement....
. It is therefore equal to 437.5 grains.

In 1958 the United States
United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
 and countries of the Commonwealth of Nations
Commonwealth of Nations

The Commonwealth of Nations, also known as the Commonwealth or the British Commonwealth, is an intergovernmental organization of fifty-three independent member states....
 agreed to define the international avoirdupois pound to be exactly 0.45359237 kilograms. Consequently, since 1958, the international avoirdupois ounce is exactly 28.349523125 grams by definition.

The ounce is commonly used as a unit of mass in the United States. On January 1, 2000 it ceased to be a legal unit of measure within the United Kingdom
United Kingdom

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom , the UK or Britain,is a sovereign state located off the northwestern coast of continental Europe....
 for economic, health, safety or administrative purposes but remains a familiar unit, especially amongst older people.

International troy ounce

A troy
Troy weight

Troy weight is a system of Physical units of mass customarily used for precious metals, black powder, and gemstones.Named after Troyes, France, the troy system of weights was known to exist in medieval times, at the celebrated fair at Troyes in North Eastern France....
 ounce (abbreviated as t oz) 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
Pound (mass)

The pound or pound-mass is a Units of measurement of massused in the Imperial unit, United States customary units and other systems of measurement....
.

Today, the troy ounce is used only to express the mass of precious metals such as gold
Gold

Gold is a chemical element with the symbol Au and atomic number 79. It is a highly sought-after precious metal, having been used as money, as a store of value, in jewelry, in sculpture, and for ornamentation since the beginning of recorded history....
, platinum
Platinum

Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements....
 or silver
Silver

Silver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal....
.

For historical measurement of gold,
  • a fine ounce is a troy ounce of 99.5% (".995") pure gold
  • a standard ounce is a troy ounce of 22 carat
    Carat (purity)

    The carat is a measure of the purity of gold alloys. In the United States and Canada, the spelling karat is used, while the spelling carat is used to refer to the measure of mass for gemstones ....
     gold, 91.66% pure (11 "fine ounces" plus one ounce of alloy
    Alloy

    An alloy is a partial or complete solid solution of one or more chemical element in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history....
     material)


Apothecaries' ounce

The obsolete apothecaries' ounce (abbreviated ) equivalent to the troy ounce, was formerly used by apothecaries (now called pharmacists or chemists).

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
Maria Theresa thaler

The Maria Theresa thaler is a silver bullionbullion coincoin that has been used in trade coin continuously since it was first minted in 1741....
, 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.

Metric ounces

Some countries have redefined their ounces to fit in with the metric system
Metric system

The metric system is an international decimalised systems of measurement, founded by France in 1791, that is the common system of Unit of measurement used by most of the world....
.

The Dutch have redefined their ounce (in Dutch
Dutch language

Dutch is a West Germanic languages spoken by over 22 million people as a first language, and about 5 million people as a second language."1% of the EU population claims to speak Dutch well enough in order to have a conversation." Outside the European Union the number of second language speakers of Dutch is very small. Most native...
, ons) as 100 gram
Gram

The gram , ; symbol g, is a Physical unit of mass.Originally defined as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre, and at the temperature of melting ice" , a gram is now defined as one one-thousandth of the SI base unit, the kilogram, or Scientific notation kg, which itself is...
s . The Dutch's metric values, such as 1 ons = 100 grams, is inherited, adopted and taught in Indonesia
Indonesia

The Republic of Indonesia , is a transcontinental country in Southeast Asia and Oceania. Comprising Islands of Indonesia, it is the world's largest Archipelago state....
 since elementary school. It is also formally written in Indonesian national dictionary (Kamus Besar Bahasa Indonesia) and elementary school's formal manual book.

East Asia
East Asia

East Asia is a subregion of Asia that can be defined in either Geography or cultural terms. Geography and geopolitically, it covers about 12,000,000 km?, or about 28 percent of the Asian continent, about 15 percent bigger than the area of Europe, though some categorize Tibet, Xinjiang, and Mongolia as Central Asia....
 has a traditional ounce, known as a tael
Tael

Tael can refer to any one of several weight units of measurement of the Far East. Most commonly, it refers to the China tael , a part of the Chinese units of measurement of weights and currency ....
, of varying value. In China
China

China is a Culture of China, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
, it has been given a metric value of 50 grams.

Other uses


Fabric Weight

Ounces are also used to express the "weight", or more accurately density, of a textile fabric in North America or Asia, 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.

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