Each cup holds 8 fluid ounces. Therefore, there are 128 fluid ounces in 1 gallon. The standard advice is to drink eight 8-ounce glasses of water a day, which is equivalent to drinking half a gallon of water per day, because a gallon is equivalent to 64 ounces.
A quart is also equal to 4 cups. Using the metric system, a quart is about the same as 1 liter, though it is actually a little bit less, with 946.35 milliliters equaling 1 quart.
The United States does not use the gallon measurement for dry goods. Gallons are used to describe liquid volumes. Liquid volumes measure how much space a liquid takes up inside a given container.
Depending on the weight of packaging, a standard US gallon weighs around 8 pounds. This weight can fluctuate depending on the temperature of the liquid.Learn more about Food Measurements