The volume of a 5-gallon jug is 20 quarts. There are 4 fluid quarts in a gallon, hence one fluid quart is equivalent to one-fourth of a gallon by definition.
By applying these equations, five gallons are equal to five times four quarts, or 20 quarts. Different from the dry quart is the fluid quart. For instance, the fluid quart is equivalent to 0.95 litres, but the dry quart is 1.10 litres. However, the ratio of 1 dry gallon to 4 dry quarts and 1 fluid gallon to 4 fluid quarts makes the two units of measurement comparable.