A gallon of gasoline, also known as petrol, weighs approximately 6 pounds. Depending on the composition of the gasoline, its specific gravity can vary between 0.71 and 0.77, and thus its weight can slightly vary as well.
Gasoline is one of the most used fuels for internal combustion engines and is primarily used in vehicle engines. The specific gravity of gasoline used for vehicles can be crudely taken as 0.74. The specific gravity of a substance is defined as the ratio of the density of that substance to the density of water at 4 degrees Celsius. Density is defined as the mass of the object per unit volume. At 4 degrees Celcius, the density of water is 1 kilogram per litre, which equates that the density of gasoline is 0.74 kilogram per litre. Since 1 kilogram is equal to 2.20462 pounds and 1 US gallon is equal to 3.79 litres, the density of gasoline can be calculated to be 6.183 pounds per gallon, for example, a gallon of gasoline weighs 6.183 pounds. Taking into consideration that the specific gravity of gasoline can be anything between 0.71 and 0.77, the weight of a gallon of gasoline can also vary between 5.93 pounds and 6.43 pounds.