You can measure a natural gas by finding its volume in cubic feet. According to Tulsa Gas Technologies, the energy output of one cubic foot of natural gas, on average, is approximately 1000 BTUs. Using this information, solve by converting from cubic feet to cubic meters and from BTUs to MMBTUs.
Convert cubic feet to cubic meters
One meter equals 3.28084 feet. Cube this number to find that one cubic meter equals 35.315 cubic feet. Multiply 35.315 cubic feet per cubic meter by 1000 BTUs per cubic foot. The foot measurements cancel each other out, and you are left with 35,315 BTUs per cubic meter. (Equation: 35.315 ft^3/m^3 x 1000 BTU/ft^3 = 35,315 BTU/m^3.)
Convert BTUs to MMBTUs
An MMBTU is one million BTUs. Therefore, 1 BTU equals 0.000001 MMBTU. Using the previous calculation of 35,315 BTUs in a cubic meter, multiply 35,315 by 0.000001 to convert to MMBTUs. The result is as follows: 35,315 BTUs equals 0.035315 MMBTU.
Use the resulting equation
With the final equation 1 m^3 natural gas = 0.035315 MMBTU, you can easily convert any quantity of natural gas in cubic meters to its approximate heat energy output in MMBTUs. This gives you your final, fully-converted figures.