US Fluid Ounce
A US fluid ounce is a unit of volume equal to 1/128 of a US gallon or approximately 29.57 milliliters. It is commonly used for measuring beverages, medicines, and personal care products in the United States.
History
The fluid ounce originally represented the volume of one ounce of water. The US fluid ounce (29.57 mL) differs slightly from the imperial fluid ounce (28.41 mL). Despite their similar names, fluid ounces measure volume while ounces measure weight.