How many bottles of water is a gallon?

The easiest way would measure it through half a liter water bottle. There are approximately 16.9 ounces(oz) of water in a 500ml water bottle.

Gallon is an imperial customary volume unit for the U.S.

As we have previously mentioned, the 16.9oz bottle is also known as 500ml in the metric system. According to U.S. standard, 1 gallon stands for 128 fluid oz.

Hence, Number of bottles in 1 gallon = 128/16.9 = 7.57 =~ 8.