Fluid ounce
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A fluid ounce is a unit of volume in both the Imperial system of units and the U.S. customary units system. However, the two measures are not quite the same:
- The Imperial fluid ounce is 1/160 of an imperial gallon or 1/20 of an imperial pint or 8 fluid drams, about 1.734 cubic inches or 28.4130625 millilitres.[1] This volume of water weighs very nearly 1 avoirdupois ounce (it is the volume occupied by one ounce at 62 °F (16.7 °C), weighed in air with brass weights).
- The U.S. fluid ounce is defined to be 1/128 of a U.S. gallon or 1/16 of a U.S. pint, exactly 1.8046875 cubic inches or 29.5735295625 milliliters. This volume of cool, pure water weighs about 1.04 avoirdupois ounces (29.5 g).
- U.S. regulation 21 CFR 101.9(b)(5)(viii) also defines a fluid ounce as exactly 30 ml, but this is for use in nutrition labeling only.[2] These two definitions, one using English units and one metric, are not meant to concur exactly and are a common source of confusion.
In either system, the unit is often abbreviated as fl. oz. or oz. fl..
[edit] References
- ^ The Units of Measurement Regulations 1995 (2000-09-20). Retrieved on April 18, 2006.
- ^ Food and Drug Administration, HHS (PDF). Retrieved on April 18, 2006.
