The US fluid ounce is a unit of volume in the US customary unit system with the symbol fl oz.
Primarily used for measuring the volume or capacity of liquids, 1 US fluid ounce is equal to 29.57353 ml. It is also equal to 1.040843 imperial fluid ounces.
1 US fluid ounce is equal to 1/16 imperial pint, 1/32 imperial quart and 1/128 imperial gallon.
The fluid ounce was originally defined by the volume taken up by one ounce of a substance. Of course this would be different depending on the density of that substance; for example England used wine whereas Scotland used water to establish this measure.
The US fluid ounce is derived from the US gallon; which was originally based on the English wine gallon (231 cubic inches).
The US liquid pint is a unit of volume in the US customary system with the symbol pt.
1 US liquid pint is equal to 1/8 US liquid gallon. This is equal to 1/2 US liquid quart, 2 US cups, 4 US gills or 16 US fluid ounces. The SI / metric equivalent is 473.1765 ml.
From the early (1707) adoption of the British wine gallon at 231 in³, the American pint was born. Where all pints are 1/8 of their respective unit system's gallon, that put the US pint at 28.875 in³.