Cups in a gallon
There are 16 cups (C) in 1 gallon (gal). Cups and gallons are measurements of volume and capacity in the US customary and imperial systems of measurement. Both these systems use different definitions of the gallon, but the relationship between gallons and cups stays the same within each system.
The US additionally has a definition of the cup called the US legal cup that varies slightly in measurement from the US customary cup. This definition is used in the US specifically for nutrition labeling. Unlike the imperial cup and the US customary cup which are based on each system's definition of the gallon, the US legal cup is used as a unit on its own, and "US legal gallons" for example, are not used. Thus, a US legal cup is not equal to 16 US customary gallons. It is actually equal to 15.7725 US customary gallons.
Cups to gallons conversion
The following converter can be used to convert from cups to gallons or gallons to cups. Just enter a value in either cups or gallons to convert between the two.
Cups to gallons conversion explained
To convert between cups and gallons we need to remember the relationship between cups and gallons:
1 C = 
gal
1 gal = 16 C
Based on this relationship, we need to divide a value in cups by 16 to convert it to gallons. To convert a value in gallons to cups, we instead multiply by 16.
Examples
1. Convert 12 cups to gallons:
12 C ÷ 16 = 0.75 gal
2. Convert 2.3 gallons to cups:
2.3 gal × 16 = 36.8 cups
Note that this conversion works for cups and gallons within the same system of measurement. 1 US cup is not equal to 16 imperial gallons. If we were trying to convert these, we would need to convert the US cup to an imperial cup before applying the conversion above.