Gallons to ounces (oz) conversion factors are listed below. To find out how many ounces in gallons, multiply the number of gallons by the conversion factor.
1 Gallon [Fluid, US] = 128 Ounces [Fluid, US]
1 Gallon [Dry, US] = 148.946 Ounces [Fluid, US]
1 Gallon [UK] = 160 Ounces [UK]
There are 128 ounces in a gallon, because from the largest to the smallest units between gallons and ounces, there are 4 quarts in a gallon, 2 pints in a quart, 2 cups in a pint and 8 ounces in a cup, that makes 4 * 2 * 2 * 8 = 128 ounces in a gallon.
Gallon is a US customary and imperial volume unit. US fluid gallon is defined to be 231 cubic inches and US dry gallon is 268.8025 cubic inches. An imperial galon is 277.4 cubic inches. The abbreviation is "gal".
Fluid ounce is an imperial and US customary volume unit. 1 US fluid ounce equals to 29.5 mL and imperial ounce equals to 28.4 mL. The abbreviation is "fl oz".