How many fluid ounces are there in one gallon?

One gallon is equivalent to 128 fluid ounces. This measurement is based on the standard U.S. liquid gallon, which divides into ounces in a well-defined manner. To put this in context, one gallon is equal to four quarts, and since each quart contains 32 fluid ounces, multiplying four quarts by 32 fluid ounces yields exactly 128 fluid ounces.

Understanding this conversion is essential in pharmacy settings, as precise measurements affect medication dosing and formulations. Other options do not reflect the correct conversion related to a gallon and may stem from miscalculations or misunderstandings of liquid measurement units.