Gas m³ to kWh converter
Turn cubic metres off the gas meter into kilowatt hours, megajoules and gigajoules, using the calorific value your own distributor published.
Energy
1,051.0467 kWh
A cubic metre of gas is not a fixed amount of energy. The calorific value moves with what is in the pipe, your distributor measures and publishes it for every gas day, and your bill prints the one it billed you on. The 37 MJ/m³ here is only the ceiling British law falls back on when the measuring gear fails.
Cost of that gas
105.10467
Kilowatt hours per m³
10.510467
This is the number a gas bill calls the conversion factor. It follows from the calorific value above, so it moves whenever that does.
Same in megajoules
3,783.768 MJ
Same in gigajoules
3.783768 GJ
Corrected volume
102.264 m³
kWh = m³ × correction × calorific value ÷ 3.6
A gas meter counts volume and a gas bill charges energy, and the step between them is the one thing nobody can write into a calculator: the calorific value of the gas that actually flowed through your pipe. It is not a constant. What comes out of a North Sea field, an LNG tanker and a biomethane plant carries different amounts of energy per cubic metre, the mix in the network changes from day to day, and so British law makes the gas transporter measure the calorific value for every gas day and publish it. Your bill prints the figure it billed you on. Put that in here with the reading off the meter and you get kilowatt hours, megajoules and gigajoules — and the kWh-per-cubic-metre factor that the bill quotes but rarely explains.
How it is calculated
kWh = m³ × correction × calorific value ÷ 3.6
Two corrections stand between a dial and a bill. The first is volume: a domestic meter measures gas at whatever temperature and pressure it happens to be at, so the reading is scaled to standard conditions. British regulations set that factor at 1.02264 for supplies under 732 000 kWh a year. The second is energy content: multiply the corrected cubic metres by the calorific value in megajoules per cubic metre and you have megajoules. Divide by 3.6 to get kilowatt hours, because NIST puts one kilowatt hour at exactly 3.6 megajoules, and by a thousand instead for gigajoules, the unit district heating is usually billed in.
Questions people ask
- Where do I find my calorific value?
- On the gas bill, usually in the small print beside the meter readings, quoted in megajoules per cubic metre or sometimes as a ready-made kWh-per-m³ factor. In Britain the transporter determines it for each gas day and the supplier averages it across your billing period; other countries do the same thing under their own rules, and some print only the finished conversion factor. If your bill gives the factor rather than the calorific value, you can put 3.6 times that factor into this page and leave the correction at 1.
- Why is the default 37 and not a typical value?
- Because 37 is a figure with a source and a "typical value" would be a figure with an author. The Gas (Calculation of Thermal Energy) Regulations 1996 name 37 megajoules per cubic metre as the cap on the value a transporter may use when its measuring apparatus has failed — a deliberately conservative floor rather than a description of the gas in your pipe. Real published values sit above it, which means leaving the default alone understates your energy. Replace it with the one on your bill.
- What is the 1.02264 for?
- It converts the volume a domestic meter registers into the volume that gas would occupy at 15 °C and 1013.25 millibars. British regulations fix it at 1.02264 for any supply expected to stay under 25 000 therms or 732 000 kilowatt hours a year; larger supplies get a calculated factor combining temperature, pressure and compressibility instead. Outside Britain the arrangement differs, and some meters correct the volume themselves — in that case set this field to 1.
- Can I compare gas and electricity with this?
- Once both are in kilowatt hours, yes, but compare prices per kWh rather than per unit, and remember that a kilowatt hour of gas burnt in a boiler is not a kilowatt hour of heat. Ecodesign has required at least 86 % seasonal efficiency from new fuel boilers since 2015, so the heat always costs more per kilowatt hour than the gas does. The heat pump page does that arithmetic on both sides if you want the comparison in full.
- What about gigajoules?
- District heating is commonly billed in gigajoules, and a cubic metre of gas is a convenient bridge between the two worlds: this page gives megajoules and gigajoules alongside the kilowatt hours, so a heating bill in GJ and a gas bill in m³ can be put side by side. One gigajoule is 277.78 kilowatt hours, which follows from the same 3.6 megajoules per kilowatt hour.
Sources
The documents this page reads its numbers out of, linked so you can check them yourself.
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Found a problem, or want more?
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