Natural gas is measured in cubic feet, cubic meters, British thermal units or joules, while gasoline is measured in gallons, British thermal units, joules or metric tons. The unit used to measure gas is dependent upon the situation in which the gas is being used.
In a commercial context, natural gas is measured in cubic feet, while gasoline is sold at the pump in gallons. Because of differences in the amount of energy produced from various energy sources and the differences in commercial measurements, comparing two energy sources requires that they both be measured in terms of energy units. British thermal units are used when comparing energy sources.