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**Historical Definitions of Ounce:**
– Historically, ounce has referred to different standards of mass in various parts of the world and for different applications.
– Various mass standards:
– International avoirdupois ounce: 28.349523125g (437.5 grains)
– International troy ounce: 31.1034768g (480 grains)
– Apothecaries ounce: 28.0668g
– Maria Theresa ounce: 28.0668g
– Spanish ounce: 28.75g
– Other historical ounces:
– Apothecaries ounce: Equivalent to the troy ounce
– Maria Theresa ounce: Equal to the weight of one Maria Theresa thaler, or 28.0668g
– Spanish ounce: 28.75g
– Tower ounce: 29 grams (abolished in favor of the Troy ounce by Henry VIII in 1527)

**Current Usage of Ounce:**
– International avoirdupois ounce:
– Defined as exactly 28.349523125g
– Standard unit in the United States
– International troy ounce:
– Equal to exactly 31.1034768g
– Used for precious metals like gold, silver, platinum
– Metric ounces:
– Some countries redefined their ounces in the metric system
– Example: German apothecaries ounce is 30 grams
– Dutch redefined their ounce as 100 grams

– Defined as 1/16 of a pound-force
– Force exerted by a mass of one avoirdupois ounce under standard gravity
– Equivalent to about 0.2780139 newtons
– Used in engineering calculations for unit conversions

**Fluid Ounce:**
– A unit of volume
– Imperial fluid ounce is 28.4130625ml
– US customary fluid ounce is 29.57353ml
– US food labeling fluid ounce is 30ml
– Used in bartending contexts

**Other Uses of Ounce:**
– Fabric weight: Ounces used to express fabric weight (e.g., 16 oz denim)
– Copper layer thickness of printed circuit boards: Measured in ounces (1 oz equals roughly 34.7µm)
– London Bullion Market Association: Market Basics
– Various references and publications related to measurements and historical uses of ounces.

Ounce (Wikipedia)

The ounce (/ˈns/) is any of several different units of mass, weight, or volume and is derived almost unchanged from the uncia, an Ancient Roman unit of measurement.

Unit systemImperial system
Unit ofMeasurement

The avoirdupois ounce (exactly 28.349523125 g) is 116 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 it is sometimes also used elsewhere in the Anglosphere.

Although the avoirdupois ounce is the mass measure used for most purposes, the 'troy ounce' of exactly 31.1034768 g is used instead for the mass of precious metals such as gold, silver, platinum, palladium, rhodium, etc.

The term 'ounce' is also used in other contexts:

Historically, a variety of different ounces measuring mass or volume were used in different jurisdictions by different trades and at different times in history.

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