Three units, three audiences
The same quantity of gas gets described three ways depending on who is talking.
Million tonnes per annum (Mtpa) is how liquefaction capacity is quoted. It is a mass flow, and it is what LNG producers, project developers and the trade press use.
Billion cubic metres per year (bcm/y) is how pipeline and gas-market people talk. It is a volume of gas at standard conditions, and it is what you need to compare an LNG terminal with a pipeline or with a country’s consumption.
Cubic metres (m³) is how ships and tanks are measured. It is a volume of liquid. A carrier’s capacity and a storage tank’s size are always in these units.
Mixing them up produces errors of a factor of hundreds, so it is worth having the conversions to hand.
The conversions
Mtpa to bcm/y: multiply by 1.36. A 10 Mtpa export terminal is about 13.6 bcm/y of gas.
bcm/y to Mtpa: divide by 1.36. A 12 bcm/y import terminal is about 8.8 Mtpa.
Cubic metres of liquid to cubic metres of gas: multiply by about 600. One cubic metre of LNG makes roughly 600 cubic metres of gas.
Cubic metres of liquid to tonnes: multiply by about 0.45. A cubic metre of LNG weighs roughly 450 kilograms, so 174,000 m³ is about 78,000 tonnes.
bcf/d to bcm/y: multiply by about 10.3. One billion cubic feet a day is about 10.3 bcm a year, which is about 7.6 Mtpa.
Worked examples
A standard cargo. A 174,000 m³ carrier arrives full. That is about 78,000 tonnes, or roughly 104 million cubic metres of gas once regasified. Eighty of those cargoes a year is about 6.2 Mtpa, which is roughly what one large liquefaction train produces.
A terminal against a country. An 8 Mtpa import terminal is about 10.9 bcm/y. Set beside a country consuming 80 bcm a year, that single terminal covers about 14 per cent of demand, which is the kind of comparison the raw Mtpa figure hides.
A train’s output in ships. A 5 Mtpa train produces about 11,100 cubic metres of LNG a day, so it fills a 174,000 m³ ship roughly every sixteen days, or about 23 cargoes a year.
Why the factors are approximate
LNG is not a pure substance. It is mostly methane with varying amounts of ethane, propane and butane, and its density and heating value shift with that mix. A leaner cargo is lighter and less energy-dense per cubic metre; a richer one is heavier.
There is also a definitional split. Some sources convert on higher heating value and others on lower, which moves the answer by several per cent. And the “standard conditions” defining a cubic metre of gas differ between regions.
The practical upshot: conversions in the range of 1.34 to 1.38 bcm per Mtpa all appear in reputable sources, and densities from about 430 to 470 kilograms per cubic metre are all plausible. Anyone quoting an LNG conversion to four significant figures is overstating what the number can carry.
What this site does
We store terminal capacity in both Mtpa and bcm/y and show both, converting at 1 Mtpa = 1.36 bcm/y when a release gives only one. That is Global Energy Monitor’s own convention, and using theirs means our totals reconcile with theirs rather than drifting by a few per cent.
Pipeline capacity is stored in bcm/y, converted from billion cubic feet per day at 1 bcf = 0.0283 bcm where that is the reported unit. Vessel capacity is stored in cubic metres of liquid and never converted into mass on a listing page, because the density assumption belongs with the reader rather than buried in a table.
Where a page does convert, it says so and states the factor. Where a source reports nothing, the field reads “Not reported” rather than being filled in by inference. Our methodology page sets out each rule.