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Fluid ounce
From Wikipedia, the free encyclopedia
(Redirected from Fl oz)
A fluid ounce is a unit of volume in both the Imperial system of units and the U.S. customary units system.
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The two types of ounces have slightly different definitions:
- 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 28.41 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. ounce is defined to be 1/128 of a U.S. gallon or 1/16 of a U.S. pint, about 1.804 cubic inches or 29.57 millilitres. This volume of cool, pure water weighs about 1.04 avoirdupois ounces (29.5 g). This also holds true for cheese as well. 16 ounces of cheese do not equal a pound. Ounces are a volumetric unit. (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 imperial 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., oz. fl., or fl oz. In the USA, it is common to refer to the unit simply as an "ounce", especially in cases where no confusion can occur with the unit of weight.
The word ounce derives originally from a word meaning "one" (originally "one" twelfth part of a troy pound)[3]. The word unit is also derived from the same original word, unus (one). [1] [2] In effect, the phrase "fluid ounce" is essentially equivalent to "liquid unit".
- ^ The Units of Measurement Regulations 1995 (2000-09-20). Retrieved on 2006-04-18.
- ^ Food and Drug Administration, HHS (PDF). Retrieved on 2006-04-18.
- ^ Definition of ounce, from the Merriam-Webster online.