**1) The imperial gallon:**The imperial gallon can be defined in terms of liter. One imperial gallon is approximate equals to 4.55 L (liter). Imperial gallon is actually defined on basis of volume of ten pounds of water at 17 °F. One of the terms is imperial fluid ounce. Imperial fluid ounce can be defined as 1 / 160 of an imperial gallon.

**2) US liquid gallon:**US liquid gallon can be defined as 231 (inches) 3. US liquid gallon is equals to exactly 3.785412 liters. Since 3.785412 liter is approximate equals to 0.13368 (feet) 3 and hence we can say that US liquid gallon is approximately equals to 0.13368 cubic feet or (feet) 3. Another term is US fluid ounce which can be defined as 1 / 128 of a US liquid gallon.

**3) US dry gallon:**US dry gallon is actually one – eighth of 2150.42 (inches)

^{3}. Thus US dry gallon can be defined as gallon equals to exactly 4.40488377086 liter or 268.8025 (inches)

^{ 3}.

Gram (symbol ‘g’) can be defined as unit of mass. In other words, gram can be described as "absolute weight of a volume of pure water equals to (the hundredth part of a meter) 3 and at temperature of melting ice. Gram can also be defined as 1 / 1000 of kilogram (10 -3 kg). Symbol for gram is "g" which is fixed by SI unit system.

Gallons are used to measure volume whereas grams are used to measure mass (weight). A gallon is approximately equals to 3780 gram.