Alcohol measurement | Imperial units | Cooking weights and measures | Units of volume | Customary units of measurement in the United States
Fluid ounce
A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl., old forms ℥, fl ℥, f℥, ƒ ℥) is a unit of volume (also called capacity) typically used for measuring liquids. The British Imperial, the United States customary, and the United States food labeling fluid ounce are the only three that are still in common use, although various definitions have been used throughout history. An imperial fluid ounce is 1⁄20 of an imperial pint, 1⁄160 of an imperial gallon or exactly 28.4130625 mL. A US customary fluid ounce is 1⁄16 of a US liquid pint and 1⁄128 of a US liquid gallon or exactly 29.5735295625 mL, making it about 4.08% larger than the imperial fluid ounce. A US food labeling fluid ounce is exactly 30 mL. (Wikipedia).
