There are approximately 1,892.7 milliliters in 1 half-gallon of volume. That works out to 3,785.4 milliliters per gallon, 1.892 liters per half-gallon and 3.785 liters per gallon.
One cup equals 236.6 milliliters, which is 0.2366 liters. A milliliter is defined as 1 cubic centimeter. Milliliters are based upon the cubic meter of volume for international units, otherwise known as the metric system. Milliliters are measured in graduated cylinders made of plastic or glass.
Gallons equal 231 cubic inches in the United States and 277.42 cubic inches in Great Britain. Commodities measured in gallons include milk, gasoline, juice and bottled water.