Gas units to kWh
Turn the gas you used, from two meter readings or a number of units, into kilowatt-hours and pounds, the way suppliers do on your bill.
The formula on your gas bill
Gas meters measure volume, but you pay for energy. Suppliers convert one to the other with a standard formula:
kWh = cubic metres × 1.02264 × calorific value ÷ 3.6
- 1.02264 is the volume correction factor, which adjusts for temperature and pressure.
- The calorific value (about 38–40 MJ/m³) is how much energy each cubic metre of gas holds. Your bill shows the figure used.
- ÷ 3.6 turns megajoules into kilowatt-hours, because 1 kWh is 3.6 MJ.
Imperial meters count hundreds of cubic feet. Multiply the units by 2.83 to get cubic metres first.
Quick conversion table
At a calorific value of 39.5 MJ/m³ and the current price cap rate of 7.97p per kWh:
| Gas used | kWh | Cost |
|---|---|---|
| 10 m³ | 112 | £8.94 |
| 50 m³ | 561 | £44.71 |
| 100 m³ | 1,122 | £89.43 |
| 250 m³ | 2,805 | £223.57 |
| 500 m³ | 5,610 | £447.14 |
| 1000 m³ | 11,221 | £894.28 |
| 10 units (×100 ft³) | 318 | £25.31 |
| 50 units (×100 ft³) | 1,588 | £126.54 |
| 100 units (×100 ft³) | 3,175 | £253.08 |
| 1 therm | 29.3 | £2.34 |
| 10 therms | 293.1 | £23.36 |
| 100 therms | 2,930.7 | £233.58 |
Ofgem's typical household uses 9,500 kWh of gas a year (see our kilowatt-hour explainer). Gas prices and the standing charge are set by the energy price cap; the default rate here is 7.97p per kWh including 5% VAT, for 1 October to 31 December 2026.
Frequently asked questions
How do I convert gas units to kWh?
For a metric meter (reading in m³): units used × 1.02264 × calorific value ÷ 3.6. With a calorific value of 39.5, 100 m³ is about 1,122 kWh. For an imperial meter (reading in hundreds of cubic feet), first multiply the units by 2.83 to get cubic metres.
What is the calorific value of gas?
It is the energy in a cubic metre of gas, in megajoules (MJ/m³). It changes slightly with the gas mix, usually somewhere around 38 to 40 MJ/m³, and your supplier prints the figure used on your bill. We use 39.5 unless you enter your own.
What is the volume correction factor?
A fixed 1.02264 that adjusts the measured gas volume for standard temperature and pressure. Suppliers use the same figure on every bill.
Is my gas meter metric or imperial?
A metric meter shows "m³" or "M3" next to the reading and usually has five digits before a red decimal section. An imperial meter shows "ft³" or "cubic feet" and usually four digits. Imperial meters count in hundreds of cubic feet.
How many kWh are in a therm?
One therm is 29.3071 kWh. Therms are still used in some business and US gas pricing.
What does 100 kWh of gas cost?
At the current price cap rate of 7.97p per kWh (including VAT), 100 kWh costs £7.97, plus the daily standing charge of 29.68p.
General information, not financial advice. Your supplier's bill is the final word on what you owe.