Your gas meter measures volume, but the tariff is in MMBTU, a unit of heat. The bill converts one to the other with the GCV (gross calorific value) printed on it. 1 hm3 is 100 cubic metres. At a GCV of 990 BTU per cubic foot, 1 hm3 is 3.514 MMBTU; at 950 it is 3.372 MMBTU.
Choose the unit you have, enter the amount and the GCV from your bill. The converter shows every other unit and the steps the gas company uses.
How the bill converts hm3 to MMBTU
SSGC's billing FAQ gives the formula, and the SNGPL and SSGC bill calculators on this site use the same steps.
- Gas used in hm3 = current reading minus previous reading. 1 hm3 = 100 standard cubic metres.
- Thousand cubic feet (MCF) = cubic metres ÷ 28.17385.
- MMBTU = MCF × GCV ÷ 1,000.
Example: 1 hm3 at GCV 990
- 1 hm3 = 100 cubic metres.
- 100 ÷ 28.17385 = 3.5494 MCF.
- 3.5494 × 990 ÷ 1,000 = 3.5139 MMBTU.
Going the other way, 10 MMBTU at GCV 990 is 10 ÷ 3.5139 = 2.846 hm3. The tariff rate per MMBTU is then applied to the MMBTU figure, slab by slab.
hm3 to MMBTU at different GCVs
GCV moves a little every month with the gas mix, so the same meter reading can give slightly different MMBTU.
| hm3 | GCV 900 | GCV 950 | GCV 990 | GCV 1,000 | GCV 1,050 |
|---|---|---|---|---|---|
| 0.5 | 1.597 | 1.686 | 1.757 | 1.775 | 1.863 |
| 1 | 3.194 | 3.372 | 3.514 | 3.549 | 3.727 |
| 1.5 | 4.792 | 5.058 | 5.271 | 5.324 | 5.590 |
| 2 | 6.389 | 6.744 | 7.028 | 7.099 | 7.454 |
| 3 | 9.583 | 10.116 | 10.542 | 10.648 | 11.181 |
| 4 | 12.778 | 13.488 | 14.056 | 14.198 | 14.907 |
A higher GCV means more heat in each cubic metre, so more MMBTU for the same volume. You pay for heat, not for volume.
Cubic feet: why the factor is 28.17385
A plain conversion gives 35.315 cubic feet in a cubic metre, or 28.317 cubic metres in 1,000 cubic feet. The gas companies' billing formula uses 28.17385 cubic metres per MCF instead, for gas measured in standard cubic metres. On a bill, use the company factor: 1 hm3 is 3,549 standard cubic feet, not 3,531.
Pressure factor
SSGC describes the pressure correction factor as the figure that converts the volume measured by the meter to standard volume. Where a bill shows one, usually for commercial and industrial connections, the meter volume is multiplied by it before the MMBTU step. If your bill shows no pressure factor, leave it at 1.
Reading your bill
Look for these lines on an SNGPL or SSGC bill:
- Previous and present readings, and the gas used in hm3.
- GCV, in BTU per standard cubic foot.
- Gas used in MMBTU, which should match hm3 × 100 ÷ 28.17385 × GCV ÷ 1,000.
If the MMBTU on the bill does not match, check whether a pressure factor has been applied or whether the reading was estimated. To price the gas, use the SNGPL bill calculator or the SSGC bill calculator, which apply the domestic slabs to the hm3 you used.
Use the GCV printed on your own bill; the default here is only a starting point from SSGC's worked rates. This converter is not affiliated with SNGPL, SSGC or OGRA.
Gas unit questions
How do I convert hm3 to MMBTU?
Multiply hm3 by 100 to get cubic metres, divide by 28.17385 to get MCF, then multiply by the GCV on your bill and divide by 1,000. At GCV 990, 1 hm3 is 3.514 MMBTU; at 950 it is 3.372 MMBTU.
What is hm3 on a gas bill?
Hundred cubic metres. One hm3 is 100 cubic metres of gas. A home using 1.5 hm3 in a month has burned 150 cubic metres, which the bill turns into MMBTU with the month's GCV.
What is GCV on a Sui gas bill?
Gross calorific value: the heat released by burning one standard cubic foot of gas, in BTU. SSGC says the GCV used for the bill is printed on each customer's bill. It changes slightly each month with the gas supplied.
How many cubic feet are in 1 hm3?
On the gas companies' billing basis, about 3,549 standard cubic feet, because they use 28.17385 cubic metres per thousand cubic feet. A plain metric conversion gives 3,531 cubic feet.
Why is my gas billed in MMBTU and not cubic metres?
OGRA fixes gas prices per MMBTU, a unit of heat. Charging for heat means you pay for the energy in the gas, whatever its quality in a given month. The meter still measures volume, so the bill converts it with the GCV.
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Last reviewed 30 September 2026. Results are estimates; official notices always take precedence.