16 CFR § 500.10 - Units of fluid measure, how expressed.
(a) Use of the terms “net” or “net contents” is optional.
(b) Declaration of net quantity of contents in terms of fluid measure shall be identified as such in each instance and the statement of U.S. gallon of 231 cubic inches and quart, pint, and fluid ounce subdivisions thereof shall be expressed as follows:
(1) If less than 1 pint, in terms of fluid ounces. (Example: “Net Contents 8 fl. oz. (236 mL)” or “Net Contents 236 mL (8 fl. oz.)”.)
(2) If at least 1 pint but less than 1 gallon, in terms of the largest whole unit (quarts, quarts and pints or pints, as appropriate), with any remainder in terms of fluid ounces or common or decimal fractions of the pint or quart, except that it shall be optional to include an immediately adjacent additional expression of net quantity in terms of fluid ounces. (Examples: “1 qt. (946 mL)” or “Net contents 1 qt. 1 pt. 8 oz./56 fl. oz. (1.65 L)”, but not in terms of quart and ounce such as “1 quart 24 ounces (1.65 L)”.)
(3) If 1 gallon or more, in terms of the largest whole unit (gallons followed by common or decimal fractions of a gallon or by the next smaller whole unit or units viz, quarts and pints) with any remainder in terms of fluid ounces or common or decimal fractions of the pint or quart, except that it shall be optional to include an immediately adjacent additional expression of net quantity in terms of fluid ounces.