Converting Gas Meter Units to kWh

Gas meters do not measure energy. They count volume, in cubic metres on newer meters or cubic feet on older ones, and the supplier then converts that volume into kilowatt hours before applying the unit rate¹. The bill that lands on the doormat is therefore the end result of a small, standard piece of arithmetic, and every number that goes into it is either printed on the bill or fixed across the industry. Both gas and electricity usage are ultimately measured in kWh, which is why the two fuels can sit side by side on one bill and be compared like for like².

The conversion itself is short. Take the volume of gas used since the last reading, multiply it by 1.02264 to correct for temperature and pressure, multiply again by the calorific value printed on the bill, and divide by 3.6³. That final figure is the kilowatt hours the supplier charges for. A householder with a calculator and a recent bill can reproduce the whole calculation in a couple of minutes, which is the point of this page: it shows how to check a supplier's arithmetic rather than take it on trust.

Why gas is billed in kilowatt hours rather than volume

A gas meter is a volume counter. Older meters measure in cubic feet and newer ones in cubic metres, while electricity meters measure directly in kWh, a distinction worth remembering whenever the two readings sit side by side¹. The reason gas cannot be metered the same way is that gas is a physical fuel whose energy content varies with its composition, its temperature and its pressure. A cubic metre of gas on a cold day does not contain exactly the same energy as a cubic metre on a warm one, and gas drawn from different sources differs slightly in quality.

So the industry bills for energy. One unit, one kilowatt hour, means the use of 1,000 watts over one hour, and that definition applies to gas and electricity alike⁶. The unit rate on a tariff is calculated in kilowatt hours, which lets a household compare a gas price with an electricity price directly, and lets the two fuels appear on one bill in the same currency². It also means the volume on the meter face has to be translated before it means anything in money.

This is why a gas bill carries more than a reading and a price. Somewhere on it, usually in small print near the calculation, are the correction factor, the calorific value and the divisor that turned the meter's numbers into billable units. Those figures are the subject of the rest of this page.

Working out whether your meter is metric or imperial

The first practical question is which kind of meter is on the wall, because the two types need different treatment. The quickest test is to count the digits. Older gas meters are measured in cubic feet and have four numbers before the decimal point; newer models have five numbers and are usually measured in cubic metres¹. Imperial meters, which include dial meters and some analogue types, show readings in cubic feet and have four numbers to read, while most gas meters are now metric, showing cubic metres with five numbers to read⁷.

Digital meters often label themselves. Digital metric gas meters measure usage in cubic metres and usually show "m" or "m3" on the display, whereas the older digital imperial style measures in cubic feet³. If the meter is a dial type, it is imperial, and reading it is its own small skill, covered in the guide to how to read a gas meter.

The meter type matters because the conversion starts from a different place. A metric reading goes straight into the formula. An imperial reading needs one extra step, converting cubic feet to cubic metres, before the standard calculation can begin³. Mixing the two up produces a figure wrong by a factor of about 35, which is far and away the most common error in a household calculation.

The four step sum, from meter reading to kWh

The industry standard formula has four steps, and each input is either fixed or printed on the bill. First, establish the volume of gas used: the current reading minus the previous one. Second, multiply by 1.02264, the volume correction factor. Third, multiply by the calorific value, which the supplier shows on the bill. Fourth, divide by 3.6 to arrive at kilowatt hours³.

Written out:

1. Volume used = current reading − previous reading
2. Corrected volume = volume used × 1.02264
3. Energy content = corrected volume × calorific value
4. kWh = energy content ÷ 3.6

The calorific value is the only input a householder cannot work out alone, and it does not need to be, because it is shown on the gas bill⁴. The correction factor and the divisor are constants of the trade: the same 1.02264 and the same 3.6 appear in every supplier's calculation³. That consistency is what makes the check possible. If a bill's arithmetic cannot be reproduced with these four steps, the question to the supplier is why not.

One point of order before starting: the volume must be the gas used in the billing period, not the cumulative total on the meter. The meter never resets, so the previous reading, usually on the last bill, has to be subtracted first. Only the difference goes through the formula.

Working through a metric meter example

For a metric meter, the reading is already in cubic metres, so the formula can be applied directly. Suppose a household's previous bill was based on a reading of 04000 and the new reading is 04100. The volume used is 100 cubic metres. The next step is to multiply that volume by the correction factor of 1.02264³. The step after that needs the calorific value from the bill, and this is where the household's own figure and the supplier's must be the same number: multiply the corrected volume by that calorific value, then divide by 3.6⁴.

The arithmetic cannot be finished here because the calorific value genuinely varies between bills and regions, and quoting a single figure as if it were universal would be misleading. What can be said is the shape of the answer: for 100 cubic metres, the kWh figure will be in the low thousands, and the supplier's bill should show exactly the same chain of multiplication. If the bill instead shows a wildly different volume, the likely explanation is that the reading was taken in the wrong units, or that an estimate rather than an actual reading was used.

For a sense of scale, Ofgem's price cap documentation works on the basis of 11,500 kWh of gas a year for a typical medium consumer, alongside 2,700 kWh of electricity⁵. A household whose own annual conversion lands near that figure is in ordinary territory; one that lands far above or below it either uses much more or less gas than typical, or has made an error in the units.

The extra step for a meter that counts cubic feet

Imperial meters need one extra step at the front of the calculation. The reading is in cubic feet, and the standard formula expects cubic metres. The conversion is a single multiplication: if the measure is in cubic feet, multiply by 2.83 to convert to metres³. The same instruction appears in independent guidance on estimating energy use, which tells householders that if an annual meter reading is in cubic feet, they should multiply by 2.83 to convert to metres before doing anything else⁴.

So the full imperial sequence is:

1. Subtract the previous reading from the current one to get cubic feet used
2. Multiply by 2.83 to get cubic metres
3. Multiply by 1.02264
4. Multiply by the calorific value from the bill
5. Divide by 3.6

One wrinkle worth knowing is that imperial gas meters often count in hundreds of cubic feet, even though gas meters are commonly described as measuring in either hundreds of cubic feet or cubic metres³. The number of digits before the decimal point is the reliable guide: four digits means cubic feet, five means cubic metres¹. A householder unsure of the units should check the bill, which states what the readings were taken in, or the meter face itself, where a metric digital meter displays "m" or "m3"³.

The 2.83 step is where most household calculations go wrong, in both directions. Applying it to a metric reading understates the gas used; omitting it on an imperial reading overstates the gas used by a factor of nearly three. Either mistake is large enough to spot immediately when the result is compared with the bill.

What the 1.02264 figure actually does

The correction factor of 1.02264 appears in every supplier's calculation, and independent guidance is consistent about it: multiply by 1.02264⁴. The same figure is given in the industry standard formula described in consumer guidance on meters³. It is not a number the supplier chooses, and it is not tailored to an individual property.

What it does is adjust the measured volume to standard conditions. Gas expands and contracts with temperature and pressure, so the volume that passes through the meter depends partly on the weather and the local network. The correction factor converts the metered volume to what the gas would occupy under standard reference conditions, so that a household is charged for the energy in the gas rather than for the happenstance of a cold month. Because it reflects average conditions across the network rather than any single home, it is the same figure for every household³.

That uniformity answers a question householders often ask: whether their correction factor might differ from a neighbour's. It does not. The part of the calculation that genuinely varies, both between homes and between billing periods, is the calorific value, which is the subject of the next section. When checking a bill, the correction factor can be taken as read: 1.02264, applied to the volume, before the calorific value is brought in⁴.

Calorific value: the one number you must read off the bill

The calorific value is the measure of how much energy a given volume of gas contains, and it is the one input in the formula that a householder must take from the bill, because it is shown there⁴. It varies because the gas in the network is not uniform: gas from different sources and blends differs slightly in energy content, and suppliers adjust the figure they use as the composition of gas in their network changes. That is why the calorific value on one bill may not match the one on the next, and why two households on different networks can see different figures for the same period.

There is also a deeper distinction in how energy content is expressed. UK practice has traditionally used gross calorific values, while most European standards use net values, and for gas appliances it is now the norm to express the rating as a net value, written kW (net)⁸. The gross figure counts the energy recoverable including the heat in the water vapour produced by combustion; the net figure excludes it. This does not change a household's bill, because the supplier's calculation uses one consistent basis, but it explains why appliance ratings and calorific values quoted in different places may not look comparable.

The calorific value also connects gas use to its carbon footprint. Official guidance puts the carbon intensity of gas at 0.185 kgCO2/kWh on a gross calorific value basis⁹, while independent statistics that include the full lifecycle give a figure of 0.213 kgCO2e/kWh for gas¹⁰. Both figures are per kWh, which is precisely why the conversion on this page matters beyond the bill: it turns meter readings into the units in which carbon, as well as money, is counted.

Checking the result against what you were charged

Once the kWh figure is calculated, the check against the bill is straightforward multiplication. Guidance on estimating energy use suggests multiplying the kWh figure by the pence per kWh rate, noting that for many people this will be around 7p per kWh⁴. The actual rate depends on the tariff and the period. Under the price cap that ran from 1 October to 31 December 2025, a typical customer on a standard variable tariff paying for gas by Direct Debit paid on average 6.29 pence per kWh, including VAT, across England, Scotland and Wales¹¹. The Welsh Government's explanation of the cap gives a gas unit rate of 5.93p per kWh for the period 1 January to 31 March 2026, alongside a standing charge of 35.09p¹².

A bill check therefore has three parts:

• Volume: does the bill use the same reading difference you calculated?
• Conversion: does the bill show a correction factor of 1.02264, a calorific value and a divisor of 3.6?³
• Rate: does the pence per kWh match your tariff, and is the standing charge applied once per day rather than per unit?

Households with a smart meter do not have to wait for a bill to see the result. The in-home display shows how much gas and electricity is being used in kilowatt hours and its cost in as near to real time as possible¹³. That display is showing the conversion already done, which makes it a useful cross-check: if the display's cumulative gas figure and a manual conversion from the meter readings are far apart, one of the two is being read in the wrong units.

Why your figure will not match the bill to the penny

Even done correctly, a household conversion will usually land close to, but not exactly on, the supplier's figure. The calorific value is the main reason: it changes over time as the gas blend changes, and the supplier applies the figure for the network area and period in question, while a householder checking later may use a rounded or superseded number⁴. Rounding at different points in the chain also produces small differences, and estimated readings in place of actual ones shift the volume itself.

The scale of typical consumption gives context for what a result should look like. Ofgem's price cap work uses 11,500 kWh of gas a year for a medium consumer⁵. The official Typical Domestic Consumption Values have been revised over the years: in 2017 the high category for gas was revised down from 18,000 to 17,000 kWh a year¹⁴, and in 2019 the 5th percentile figure was revised up from 2,500 to 3,000 kWh, with the 95th percentile at 29,000 kWh¹⁵. Ofgem has also set a threshold for what counts as a material change to these values: at least 500 kWh for gas when rounded¹⁶. Older official bill tables used different assumptions again, with 2011 bills calculated on 18,000 kWh a year¹⁷ and 2014 bills on 15,000 kWh¹⁸.

What the kWh number tells you about your home

Once meter readings are in kWh, a household can place its own use against the benchmarks above and see whether it sits nearer the 3,000 kWh end of the distribution or the 29,000 kWh end¹⁵. That single number is the foundation of almost every comparison worth making: how much a tariff change would cost, whether a grant scheme's consumption assumptions fit the home, and how the household stacks up against the 11,500 kWh medium figure the price cap documentation works from⁵.

Converted figures also let gas and electricity be compared in the same units, and the price gap between the two fuels is large. Official Scottish Government strategy documents note that one kWh of electricity is currently more expensive than one kWh of gas by a factor of about 4 to 5¹⁹. That ratio is the reason fuel choice, not just quantity, drives heating bills, and it is only visible once both fuels are measured in kWh.

The same unit underpins how buildings are assessed. Energy use intensity, the measure used in energy performance policy, is expressed in kWh per square metre, and when energy use is measured in those units it is known as energy use intensity or EUI²⁰. Industry guidance likewise measures building energy performance as kilowatt hours per hour per metre squared per year, written kWh/m2/pa²¹. A household that knows its annual gas kWh and its floor area can produce the same figure for its own home.

Verifying your own bill as a step toward independence

Understanding the conversion is a small piece of household sovereignty over its own energy data. A householder who can reproduce the bill's arithmetic is not dependent on the supplier's say-so for what was used and what it cost, and can query a bill that does not add up rather than pay it. The same skill transfers to any metered energy: official guidance on metering for payment schemes notes that heat and electricity meters should be in kilowatt hours or megawatt hours, while gas and oil meters record in cubic metres or litres²², so volume-to-energy conversions recur wherever a home generates or stores heat.

The conversion also makes the dependence itself visible. Gas arriving by pipe is a continuous dependence on a supplier, a network and a unit rate the household does not set, and the kWh figure quantifies exactly how much of that dependence is being consumed each quarter. The carbon figures attached to each kWh, 0.185 kgCO2/kWh on a gross basis in official guidance⁹ and 0.213 kgCO2e/kWh in independent statistics¹⁰, give the same visibility on emissions. A home that cuts its gas kWh, by insulation, better controls or a move to electric heating, is cutting both its bill and its exposure to a fuel whose price it cannot influence; analysis by the Energy Systems Catapult has pointed to shifts in bill charges that could favour low carbon heating²³.

What the conversion cannot do is remove the dependence. The meter belongs to the network, the calorific value is set by the supplier, and the unit rate is set by the market and the cap. What a household gains is the ability to verify, to compare and to decide with its own numbers, which is the starting point for every larger step toward taking more control of your home's energy.