Gas Cost Calculator
From two gas meter readings to kilowatt-hours and a cost, with the conversion figure your bill gives in m³ or cubic feet.
Runs entirely in your browser. Nothing is uploaded, logged or stored.
Cost of the gas
134.40
- Energy used
- 1,120.0 kWh
- Volume used
- 100.00 m³
- With the standing charge
- What each kilowatt-hour cost, standing charge included
A gas meter counts a volume, and the bill charges for energy. Give two readings and the conversion figure printed on your bill, and this gives the kilowatt-hours in between and what they cost at your price.
How it works
The volume is the difference between the two readings. A meter counting hundreds of cubic feet is converted at 2.8316846592 m³ for each hundred, which is exact: a foot is 0.3048 m by definition.
A conversion coefficient in kWh per m³, as French bills give it, multiplies the volume directly: it already includes the energy in a cubic metre of your gas and the correction for your altitude.
A calorific value in MJ per m³, as British bills give it, goes through the formula of the 1996 regulations: the volume times the correction factor 1.02264, times the calorific value, divided by 3.6 to turn megajoules into kilowatt-hours.
Examples
| Case | Input | Result |
|---|---|---|
| A French bill | 100 m³ at a coefficient of 11.2, 0.12 per kWh | 1,120.0 kWh — 134.40 |
| A British bill | 100 m³ at a calorific value of 39.5 MJ/m³ | 1,122.1 kWh |
| An imperial meter | 35 hundred cubic feet | 99.11 m³ |
Frequently asked questions
Where do I find the conversion figure?
On your bill, next to the readings: a coefficient in kWh per m³ on a French bill, a calorific value in MJ per m³ on a British one. It changes with where you live and with the month, because the gas itself does, so use the one printed for the period you are working out.
Why does it not use an average figure?
Because there is no single one to use. The energy in a cubic metre of gas depends on where the gas came from, and the coefficient also depends on your altitude. A figure that is right for one address and one month is wrong for others, and yours is on your bill.
My bill is in therms. Can I use it?
Not directly: this page starts from the meter. A therm is 105.505 MJ, about 29.31 kWh, so multiplying the therms on your bill by 29.31 gives the kilowatt-hours to price.
Good to know
- The figures the page opens on — the readings, the coefficient and the price — are an example, not anybody's bill.