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MasterMath

Gas Usage Calculator

From the cubic metres on the meter to the kilowatt hours the supplier bills, and what they cost.

Currency and number format for

Energy used

—

Energy used—
Cost of that energy—
Per day—
Cubic metres per day—
Equivalent in heating oil—
Or in butane—

How this was worked out

    Indicative result. The conversion factor is not universal: it depends on the calorific value of the gas supplied and on a correction for pressure and temperature, and it is printed on your bill. The default here is a reference, not a claim.

    The formula

    kWh = cubic metres × conversion factor

    Where it comes from

    A gas meter measures volume and the bill charges energy, so somewhere there is a conversion. The bridge is the conversion factor, which combines the calorific value of the gas supplied with a correction for pressure and temperature, and it is printed on the bill itself: it usually runs around 11.7 kWh per cubic metre, but it varies between areas and between months. That is why it is a field here and not a constant: using another region’s figure can throw the sum out by five per cent.

    How to work it out by hand

    1. Note the meter reading in cubic metres
    2. Find the conversion factor on your bill
    3. Multiply: those are the kilowatt hours
    4. Multiply by the price per kWh for the cost

    What is worth knowing

    The equivalences are there for making an informed comparison with another fuel. A litre of heating oil holds about 10 kWh and a kilo of butane about 12.7, so a hundred cubic metres of natural gas is roughly 117 litres of oil. But comparing energy alone is incomplete: boiler efficiency and the fixed cost of each supply change the answer. And a word on the meter: if the supplier estimates the reading rather than taking it, the following period reconciles the difference and can produce a shock that has nothing to do with that month’s actual usage.

    Frequently asked questions

    How do I convert gas m³ to kWh?

    Multiply by the conversion factor on your bill, which usually runs around 11.7 kWh per cubic metre.

    Why is the conversion factor not fixed?

    Because it depends on the calorific value of the gas supplied and on a correction for pressure and temperature, which vary by area and period.

    How many kWh is 100 m³ of gas?

    Around 1,170 at a factor of 11.7. At a factor of 10.5 it would be 1,050: the difference is not trivial.

    What is a cubic metre of natural gas worth in energy?

    About 11.7 kWh, roughly 1.2 litres of heating oil or a little under a kilo of butane.

    Why did I suddenly get a very large bill?

    It may be a reconciliation: if the previous period was estimated rather than read, the difference is charged afterwards.