A gallon of water contains 128 fluid ounces. The number of bottles of water in a gallon depends on the size of the bottle:

• For standard 16.9 oz (500 ml) water bottles, it takes about 7.5 to 7.57 bottles to make a gallon

• For 16 oz bottles, it takes exactly 8 bottles to make a gallon

• For other bottle sizes, you can calculate the number by dividing 128 (ounces in a gallon) by the ounces per bottle. For example:
  • 8 oz bottles: 16 bottles per gallon
  • 12 oz bottles: about 10.67 bottles per gallon
  • 20 oz bottles: 6.4 bottles per gallon
  • 24 oz bottles: 5.33 bottles per gallon
  • 30 oz bottles: about 4.27 bottles per gallon

• For metric sizes:
  • 500 ml bottles (about 16.9 oz): ~7.57 bottles per gallon
  • 750 ml bottles: about 5 bottles per gallon
  • 1000 ml (1 liter) bottles: about 4 bottles per gallon

In summary, if you are using the common 16.9 oz water bottle, expect roughly 7.5 bottles to equal one gallon of water. For 16 oz bottles, it is exactly 8 bottles per gallon. For other sizes, divide 128 by the bottle size in ounces to get the precise number.