Gallons to cups conversion factors are listed below (for US, UK and for both fluid and dry measurements). To find out how many cups in a gallon, multiply by the conversion factor or use the converter if the conversion is from US fluid gallons to US cups.
1 Gallon [Fluid, US] = 16 Cups [US]
1 Gallon [Dry, US] = 18.618355 Cups [US]
1 Gallon [UK] = 18.18436 Cups [Metric]
There are 16 cups in a gallon, because from the largest to the smallest units from gallon to cup, there are 4 quarts in a gallon, 2 pints in a quart and 2 cups in each pint, that makes 4 * 2 * 2 = 16 cups in a gallon.
For example, to find out how many cups of water there are in a gallon and a half, multiply the gallon value by the conversion factor, that makes 1.5 gal * 16 = 24 cups in a gallon and a half.
For US fluid gallons, there are 2 cups in 1/8 US gallon, 4 cups in a quarter (1/4) US gallon, 5.3 cups in 1/3 US gallon, 10.6 cups in 2/3 US gallon and 12 cups in 3/4 US gallon.
For UK gallons, there are just about 2.3 cups in 1/8 UK gallon, 4.5 cups in a quarter (1/4) UK gallon, 6 cups in 1/3 UK gallon, 12 cups in 2/3 UK gallon and 13.5 cups in 3/4 UK gallon.
Gallon is an imperial and US customary volume measurement unit. Imperial gallons are used for both fluid and dry volume measurement but US customary system have different gallons for dry and fluid volume measurements. 1 US fluid gallon is 3.785 liters, 1 US dry gallon is 4.4 liters and 1 imperial (UK) gallon is 4.546 liters. The abbreviation for gallon is "gal".
Cup is a volume unit and used mostly to measure liquid and bulk, dry foods. The imperial and the Canadian cups are no longer in use and replaced by metric cups (250 mL). There are 16 cups in a US liquid gallon and about 18.5 cups in a US dry gallon. There are 18.2 metric cups and 16 imperial cups (284 mL) in an imperial gallon (4546 mL). The abbreviation for cup is "c".