A gallon is a unit of volume measurement used in the United States and Canada. It’s equal to 128 ounces, or 3.785 liters (L). A gallon is about 4 quarts, about 1/4 of a cubic foot, and can describe almost anything that holds liquid, including water bottles and milk jugs.
A quart is another standard liquid measurement smaller than a gallon; most prefer using quarts over gallons because they’re easier to remember and measure when cooking or at home.