A gallon is 231 cubic inches, which equals 128.54 cubic centimeters. That means that there are 128 of these imaginary units in a gallon, but there are also 9 quarts in a gallon. One quart can be defined as 1/2 U.S. liquid gallon or 2 cups of water, making it about 1/8 as large as the unit we know as a quart today!
On average, one U.S liquid quart contains 473 grams and 629 milliliters of water each (473 ml is also known as a pint). This equates to about 1.05 quarts of water. So, one U.S. liquid quart of water weighs about 9 pounds and 1 ounce (1 pound is roughly 454 grams). This same amount of water can be divided into approximately 2 pint-sized U.S glasses, with one glass holding a half-quart and the other half-a-pint (473 ml divided by 2 equals 233 ml, which is roughly a half-a-pint each).
So, how many U.S. liquid gallons are in a gallon? One gallon has 231 cubic inches, making it approximately 1/16 of an imperial gallon (32 U.S. fluid ounces). A quart is defined as 1/2 imperial pint or 2 cups of water, so one U.S. pint is a quarter-a-pint of water (473 ml), and one quart is roughly a half-a-pint or 236 ml in volume. This means that one U.S. gallon is 128 quarts or 128/128 quart-pint-size units of water.
How many fluid ounces are there in a gallon? One imperial quart of water weighs 1 pound and 5 ounces (1.05 pounds), meaning that one U.S gallon holds 8 pounds and 12 ounces of water (1 pound is roughly 454 grams). There are 128 quarts in a gallon, so this means that a U.S liquid gallon weighs about 10 pounds and 7 ounces, or just over 4 kilograms per liter.