convert mg/kg to gallons
Best Answer: Gallon is a unit of volume, Kg is a unit of weight (mass). Considering a liter weighing 1 Kg (water for instance), then a gallon weighs 3.7854118 Kg. To expand upon Robert's answer... A kilogram is a mass; a gallon is a volume - to convert between the two you need to know the density of the liquid. Then, you can take 1 gallon, multiply by density (make sure it's in the form kg/gallon - you may need to do some conversions) and you'll get mass. anonymous Â· 9 years ago.