Fluid ounce
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A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl.) is a unit of volume equal to about 29.57 ml, in the US. It is used in both the imperial and the US customary systems, and it is sometimes referred to simply as an ounce in cases where no confusion with the unit of weight (also called an ounce) is likely to occur.
[edit] Definitions and equivalences
- Imperial fluid ounce
-
1 imperial fluid ounce = 1⁄160 imperial gallon = 1⁄20 imperial pint = 1⁄5 imperial gill = 8 imperial fluid drams ≈ 28.4130625 millilitres[1] (cm³) ≈ 1.733871455 cubic inches = 1 avoirdupois ounce of water at 62 °F (16.7 °C)[2] ≈ 0.960759940 US fluid ounce
- US customary fluid ounce
-
1 US fluid ounce = 1⁄128 US gallon = 1⁄32 US quart = 1⁄16 US pint = 1⁄8 US cup = 1⁄4 US gill = 2 tablespoons = 6 teaspoons = 8 US fluid drams ≈ 1.80468754 cubic inches[3] ≈ 29.5735295625 millilitres (or the same number of cubic centimetres (cm³)) ≈ 1.040842731 imperial fluid ounces ≈ 1.041 avoirdupois ounce (29.5 g) of water at 62 °F (16.7 °C)
- US food labeling fluid ounce
- US regulation 21 CFR 101.9(b)(5)(viii) also defines a fluid ounce as exactly 30 millilitres, but this is for use in nutrition labeling only.[4] This is not meant to concur with the customary US definition exactly but is a common source of confusion.[citation needed]
- Other useful conversions
Given the definitions above, the number of US fluid ounces in one litre is:
- 1 fl oz⁄29.57353 ml × 1000 ml⁄l = 33.8140 fl oz⁄l
There are thus about 34 customary US fluid ounces in one litre.
Similarly, there are exactly 33 1⁄3 US food-labelling fluid ounces in a litre.
[edit] References and notes
- ^ a b "The Units of Measurement Regulations 1995 (Schedule)". 2000-09-20. http://www.opsi.gov.uk/si/si1995/Uksi_19951804_en_2.htm. Retrieved 2006-04-18.
- ^ The imperial gallon was originally defined as the volume occupied by ten avoirdupois pounds of water at 62 °F (16.7 °C), weighed in air with brass weights.
- ^ a b One US gallon is defined as 231 cubic inches.
- ^ "Food and Drug Administration, HHS" (PDF). http://a257.g.akamaitech.net/7/257/2422/01apr20051500/edocket.access.gpo.gov/cfr_2005/aprqtr/pdf/21cfr101.9.pdf. Retrieved 2006-04-18.
