is mmbtu the same as mbtu?
But while the equations look the same, they use MMBTU as the units. They do take the extra step to note: MMBtu = 1 million Btu. MBTU commonly means mega or "M" BTU (x10^6) or 1 million BTU. But it sometimes means "M" for mille or Roman numerals M, which is (x10^3) 1 thousand BTU.