This conversion depends upon several factors, such as the kind of gas, possibly the current temperature of the fuel, and the efficiency of the machine that will convert it to energy.  For example, gasoline and natural gas will have different energy densities.  If natural gas is involved, then the amount of natural gas per cubic meter will depend upon the current temperature.  If you are wondering how much energy will be produced in a furnace using a specified amount of natural gas, then that depends upon the efficiency of the furnace.  This kind of conversion is currently beyond the scope of the ConvertIt measurement conversion calculator.