How Many Ounces Does A Gallon Make Up?

One US gallon is equal to 128 ounces In the British system, a gallon of water weighs 10lbs or 160 ounces, so there are 160 fluid ounces in a gallon, and 20 fluid ounces in a pint. From this we know that a fluid ounce of water does actually weigh an ounce.
Thus, an American fluid ounce is bigger than the British fluid ounce by almost about 4%. And an American fluid ounce of water doesn't weight an ounce.
So, the result is that the US gallon is 83.267% of the British gallon. In other terms, we can say that the British gallon is about a 5th greater than the US gallon, and the US gallon is about 5/6 of the British gallon or a little less then 7 British pints.

If I have to drink 1/2 gallon of water how many water bottles is that?.