The fluid ounce (US) is a unit of volume in the United States customary system. It is defined as **29.5735 milliliters ** (mL). It is not an SI unit but is widely used in the U.S. for measuring liquids.
The fluid ounce has roots in the English system and was standardized in the 19th century. The U.S. fluid ounce was defined in the 1866 Metric Law, which set the equivalency to metric measurements. Prior to this, the measurement varied regionally.
Fluid ounces are primarily used in the U.S. for measuring beverages, cooking ingredients, and pharmaceuticals. Common in recipes and nutrition labels, this unit is essential in everyday life, especially in food and drink industries.