🇬🇧 UK

How do you convert a gas meter reading to kWh?

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GlobalPublished 6 October 2026 · Written by BuyMeWhiskey Editorial Team · How we check facts

For a UK gas bill, subtract the old meter reading from the new one, convert imperial units to cubic metres when needed, apply the bill’s calorific value and correction factor, then divide by 3.6. Your supplier bills gas in kWh, not raw meter units.

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Use your current and previous gas readings and the conversion details printed on your bill to check your supplier’s calculation.

Check gas meter calculations on GOV.UK

Why the meter does not simply show kWh

A gas meter measures volume, while domestic gas bills are normally charged in kilowatt hours. GOV.UK explains that the conversion is prescribed under the Gas (Calculation of Thermal Energy) Regulations 1996. That is why the number on the physical meter does not directly equal the number of kWh on the bill.

Step 1: find units used

Subtract the previous meter reading from the current reading. GOV.UK says the black digits are the readings supplied for these examples; red digits or decimal parts are generally ignored in the meter-reading process described for household meters.

For a metric meter, the units are cubic metres. For an imperial meter, the meter records hundreds of cubic feet or cubic feet depending on the display format. The conversion path is different, so first identify which meter you have.

Metric meter formula

For a metric meter, the core formula is:

kWh = units used × calorific value × volume-correction factor ÷ 3.6

GOV.UK states that the volume-correction factor is 1.02264 and that the calorific value printed on the bill represents the gas supplied to the property. The calorific value varies, so the figure on your own bill is the one to use.

Imperial meter formula

For an imperial meter, GOV.UK says the cubic-feet reading is first converted to cubic metres using the conversion factor 0.0283 cubic metres per cubic foot. It also gives the useful shortcut that 100 cubic feet equals 2.83 cubic metres.

After that, you apply the calorific value and the 1.02264 volume correction, then divide by 3.6 to reach kWh. An imperial reading should therefore never be treated as though it were already cubic metres.

Why the calorific value is not always the same

The calorific value measures the available heat energy in the gas. GOV.UK says the quoted figure on a bill is generally an average of the gas supplied to the property. It also explains that transporters are required to maintain the value within the regulated range used for domestic gas quality.

This is why a shortcut such as “one unit always equals exactly the same number of kWh” is only an approximation. For a precise bill check, use the exact calorific value printed by your supplier.

Then calculate the cost

Once you have kWh, multiply by the gas unit rate on your bill. You may also have a standing charge, which is separate from the consumption charge. Ofgem's current price-cap table for 1 October to 31 December 2026 shows an average gas unit price of 7.97 pence per kWh and an average daily standing charge of 29.68 pence for direct-debit customers. These are average cap figures, not necessarily your tariff.

Ofgem notes that the price cap is not a universal bill price. Your actual rate depends on your tariff, region and payment method. That is why your own bill should be used for a supplier-specific check.

What if you have a smart meter?

A smart meter may make the conversion less visible because the information sent to the supplier is already used to produce kWh billing. You can still compare the readings shown by the meter or in your supplier's app with the usage on the bill. If something does not reconcile, ask the supplier for the bill calculation rather than trying to infer a hidden rate.

When to challenge the calculation

GOV.UK says billing complaints should first go to the supplier. If the issue is not resolved, Citizens Advice can provide independent energy advice and the Energy Ombudsman may investigate eligible unresolved disputes. Keep photographs of meter readings and copies of bills when checking a disputed period.

Worked example

Illustrative calculation: suppose a metric gas meter moved from 500 m³ to 625 m³, so the consumption is 625 − 500 = 125 m³. Suppose the bill shows a calorific value of 39.5 MJ/m³. These inputs are illustrative.

Energy before the final conversion: 125 × 39.5 × 1.02264 = 5,049.285 MJ approximately.
Converted to kWh: 5,049.285 ÷ 3.6 = 1,402.58 kWh approximately.
Using Ofgem's average 7.97p/kWh gas cap figure for 1 October to 31 December 2026 as an illustrative benchmark: 1,402.58 × £0.0797 = £111.79 approximately.

A 30-day standing charge at 29.68p a day would be 30 × £0.2968 = £8.90, giving a consumption-plus-standing-charge illustration of about £120.69. Your supplier's actual rate and standing charge may differ.

The purpose of the example is to show the order of operations. For a real bill, use the meter type and calorific value printed or stated by the supplier, then use the unit rate that actually appears on your tariff. Ofgem’s cap figures are benchmarks, not a substitute for your bill.

How are gas meter units converted into kWh?#

For a metric meter, take the units used, multiply by the calorific value shown on your bill and by the prescribed volume-correction factor of 1.02264, then divide by 3.6. For an imperial meter, convert the cubic-feet units to cubic metres first. GOV.UK sets out the full calculation used for domestic gas billing.

How do I calculate gas usage from two meter readings?#

Subtract the previous reading from the current reading. The result is the number of meter units used over the billing period. You then convert those units into kWh using the appropriate metric or imperial formula and the calorific value shown on the bill. Keep the readings dated so you can compare them with the supplier’s billing period.

What is the 1.02264 gas conversion factor?#

It is the prescribed volume-correction factor used in the UK gas-billing calculation. GOV.UK explains that it corrects the gas volume for temperature and pressure. It is applied after converting the meter units to the relevant volume measure and before dividing the energy figure by 3.6 to produce kWh.

What calorific value should I use for my gas bill?#

Use the calorific value shown on the bill for the gas supplied to your property. The figure can vary because gas does not have one fixed energy content per cubic metre. Using a generic constant instead of the bill’s own figure may produce a result that is close but not identical to the supplier’s calculation.

How much does one kWh of gas cost in October 2026?#

Ofgem’s table gives an average price-cap gas unit rate of 7.97 pence per kWh for direct-debit customers from 1 October to 31 December 2026. That is an average cap figure, not a universal tariff. Your actual rate can differ by region, payment method and tariff.

Why does my gas bill show kWh when my meter shows cubic metres?#

The meter measures gas volume, while suppliers bill energy. Converting the volume into kWh makes different gas supplies comparable on an energy basis. The calculation uses the measured volume, the gas calorific value and regulated conversion factors rather than treating one cubic metre as a fixed amount of energy.

What should I do if my supplier’s gas bill calculation looks wrong?#

Take a dated meter reading and compare the current and previous readings with the billing period on the bill. Check the metric or imperial meter type and the calorific value. Ask the supplier for its calculation if it still does not match. Citizens Advice can provide independent support, and unresolved eligible disputes can be taken to the Energy Ombudsman.

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Next question →Are water meters cheaper, and how are they read?

Sources

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General information, not personal financial advice. Rules depend on your circumstances; check the official source or speak to a regulated adviser before acting.