It takes approximately two and a half 750 milliliter bottles to make a half gallon. To get the number of bottles needed to make half a gallon, the gallon has to be converted to milliliters, divided by 2 to get half of it and then divided by the number 750.
One gallon translates to 3,785.41178 milliliters. This means that 1,892.70589 milliliters make half a gallon. Dividing that value with 750 yields the number 2.523607853. Upon rounding the number to two decimals, the result is 2.52, which represents the number of 750 milliliter bottles that are needed to make half a gallon.