Cubic feet of natural gas to gigajoules conversion calculator above calculates how many gigajoules are in 'X' cubic feet of natural gas (where 'X' is the number of cubic feet of natural gas to convert to gigajoules). In order to convert a value from cubic feet of natural gas to gigajoules just type the number of cubic feet of natural gas to be converted to GJ and then click on the 'convert' button.