Gas Unit Converter
HM3, cubic metres, cubic feet and MMBTU, converted in both directions. Volume conversions are exact; anything involving MMBTU depends on the heating value, which you can set to the figure printed on your own bill.
Convert
Fixed relationships
- 1 HM3
- 100 m³
- 1 m³
- 35.3147 cft
- 1 HM3
- 3,531.5 cft
- 1 HM3Depends on heating value
- 3.53 MMBTU
1 HM3 equals
3.53 MMBTU
The energy unit your gas charge is priced in.
The same amount in every unit
- Hundred cubic metresThe unit printed on your SSGC bill. 1 HM3 = 100 cubic metres.
- 1 HM3
- Cubic metresWhat your gas meter dial actually counts.
- 100 M3
- Cubic feetUsed by older meters and most appliance ratings.
- 3,531.47 CFT
- Million British Thermal UnitsThe energy unit your gas charge is priced in.
- 3.53 MMBTU
HM3, cubic metres and cubic feet are pure volume, so those conversions are exact. MMBTU is energy, so it depends on the heating value of the gas supplied to your area — currently set to 3.53 MMBTU per HM3.
Why your meter and your bill disagree
Your meter counts volume — cubic metres, grouped into HM3. The tariff is priced per MMBTU, which is energy. The heating value is the bridge between the two, which is why the same number of units can cost slightly different amounts in different months.
Quick reference for a domestic home
A small household on a stove and geyser typically uses somewhere between half an HM3 and three HM3 a month, rising sharply in winter. That range crosses several slab boundaries — which is exactly why winter bills feel disproportionate.
What each unit measures, and when you meet it
Gas billing mixes volume and energy in the same document, which is the source of most of the confusion.
Cubic metres (m³)
What the dials on your meter physically count. If you want to check your own consumption between two dates, this is the number you write down.
Hundred cubic metres (HM3)
One hundred cubic metres. SSGC bills in this unit, so your monthly consumption reads as a small number like 1.4 rather than 140.
Cubic feet (CFT)
The imperial equivalent — 35.3147 cft to the cubic metre. Older meters and most appliance ratings use it.
Million BTU (MMBTU)
An energy unit. Your gas charge is priced per MMBTU, so the bill converts your volume into energy using the month’s heating value before applying the slab rate.
The heating value is the only variable
Volume-to-volume conversions never change: 1 HM3 is always 100 m³ and always 3,531.5 cft. But volume-to-energy depends on what is actually in the gas, which varies by field and by month. That is the heating value, and SSGC prints the one it applied on your bill. Using your own figure instead of our default makes the MMBTU conversion exact for your account.
Common conversions at a glance
Volume rows are exact. MMBTU rows use a heating value of 3.53 MMBTU per HM3.
| HM3 | Cubic metres | Cubic feet | MMBTU (approx.) |
|---|---|---|---|
| 0.25 | 25 | 883 | 0.88 |
| 0.50 | 50 | 1,766 | 1.77 |
| 0.60 | 60 | 2,119 | 2.12 |
| 0.90 | 90 | 3,178 | 3.18 |
| 1.00 | 100 | 3,531 | 3.53 |
| 1.50 | 150 | 5,297 | 5.30 |
| 2.00 | 200 | 7,063 | 7.06 |
| 3.00 | 300 | 10,594 | 10.59 |
| 4.00 | 400 | 14,126 | 14.12 |
| 5.00 | 500 | 17,657 | 17.65 |
Unit conversion questions
What does HM3 mean on an SSGC bill?
HM3 is hundred cubic metres. Your meter counts cubic metres, and SSGC groups them in hundreds for billing — so 1 HM3 is 100 cubic metres. It is a volume unit, not an energy unit, which is why the bill converts it again before pricing it.
How many MMBTU is one HM3?
Around 3.53 MMBTU, but it is not a fixed constant. MMBTU measures energy, and the energy in a given volume of gas depends on its composition — expressed as the heating value for your area that month. SSGC prints the figure it used on your bill; type that into the converter for an exact answer.
How many cubic feet is one cubic metre?
35.3147 cubic feet, exactly. This one really is a constant: it is a pure unit conversion with no gas properties involved. So 1 HM3 works out to 3,531.5 cubic feet.
Why does my bill quote both HM3 and MMBTU?
Because two different things are being measured. The HM3 figure is what your meter physically recorded. The MMBTU figure is that volume converted into energy, and the tariff rate is priced per MMBTU. Both belong on the bill so you can follow the arithmetic — see the tariff guide for the full worked example.
My old meter reads in cubic feet. How do I compare?
Convert your cubic feet to HM3 in the converter above, then feed that into the bill calculator. Older CFT meters are still in service in some areas, and SSGC converts the reading before billing — so working in HM3 is the way to compare against your bill.