Last reviewed: June 2026 | Source: Ofgem / gov.uk / Gas (Meters) Regulations
TL;DR- Gas meters measure volume (cubic metres or cubic feet), not energy. Energy suppliers convert to kWh to calculate your bill.
- The standard UK conversion formula is: units used × calorific value × 1.02264 ÷ 3.6 = kWh.
- Calorific value varies by region and is published monthly by National Gas. The typical value is around 39.5 MJ/m³.
- For a quick estimate: multiply cubic metres by 11.2 to get approximate kWh.
- This conversion is regulated under the Gas (Meters) Regulations 1983 and Gas Act 1986 and must be applied consistently by all licensed gas suppliers.
Key Facts
●Formula (metric): units (m³) × CV × 1.02264 ÷ 3.6 = kWh
●Formula (imperial): units (ft³) × 2.83 × CV × 1.02264 ÷ 3.6 = kWh
●Typical calorific value: ~39.5 MJ/m³ (varies by region/season)
●Volume correction factor (VCF): 1.02264
●Quick estimate: 1 m³ gas ≈ 11.2 kWh
●Regulator: Ofgem / Gas Act 1986
Why Gas Is Measured in Cubic Metres but Billed in kWh
Gas meters measure the volume of gas that flows through them, expressed in either cubic metres (m³) on modern metric meters or cubic feet (ft³) on older imperial meters. However, energy is not a function of volume alone -- the energy content of a given volume of gas depends on the calorific value (CV) of the gas, which varies slightly depending on the composition of gas in the network, the temperature and the atmospheric pressure at the time of delivery.
Energy suppliers are required by the Gas Act 1986 and associated regulations to bill customers in kilowatt hours (kWh), which is a measure of energy rather than volume. To convert from the volume measured by the meter to the kWh shown on the bill, suppliers apply a conversion formula that accounts for the calorific value of the gas and two correction factors.
The Gas to kWh Conversion Formula
The standard formula used by UK energy suppliers to convert gas meter readings to kWh is:
kWh = Units used (m³) × Calorific Value (MJ/m³) × Volume Correction Factor ÷ 3.6
Breaking this down: the units used is simply the difference between the current and previous meter readings. The calorific value (CV) is the energy content of the gas, typically around 39.5 MJ/m³ in the UK but varying by region and published monthly by National Gas (formerly National Grid Gas Transmission). The volume correction factor (VCF) of 1.02264 adjusts the measured volume from the meter conditions (temperature and pressure at the meter) to standard conditions. Dividing by 3.6 converts megajoules to kilowatt hours (since 1 kWh = 3.6 MJ).
Worked Example: Converting Cubic Metres to kWh
If a gas meter reads 1,200 m³ at the start of a period and 1,250 m³ at the end, the units used are 50 m³. Using a calorific value of 39.5 MJ/m³ and the standard VCF of 1.02264:
50 × 39.5 × 1.02264 ÷ 3.6 = 560.6 kWh (approximately).
At the 2026/27 Ofgem price cap unit rate for gas of approximately 6.99p per kWh, this would cost around £39.20 in gas charges (plus the daily standing charge).
Converting Imperial (Cubic Feet) to kWh
Older imperial gas meters measure in cubic feet. To convert cubic feet to kWh, an additional step is needed to convert cubic feet to cubic metres (1 cubic foot = 0.0283168 m³, or approximately 1/35.315). The formula is:
kWh = Units used (ft³) × 2.83 × CV (MJ/m³) × 1.02264 ÷ 3.6
The factor 2.83 is a simplified conversion from cubic feet to cubic metres (100 ft³ = 2.83 m³). If a meter reads in hundreds of cubic feet, multiply the reading difference by 100 before applying the factor.
Where to Find the Calorific Value for Your Area
The calorific value used in your bill is the value applicable to your local gas distribution network zone at the time of supply. National Gas publishes monthly calorific values by local distribution zone on its website. The value used should appear on your energy bill or statement. If it does not, contact your supplier and ask which CV was applied to a specific billing period. Suppliers are required to use the correct CV for the relevant period and location.
Checking Your Gas Bill Conversion
Your gas bill should show the meter reading (in m³ or ft³), the units used, the calorific value applied, the kWh total, the unit rate in pence per kWh, and the standing charge. If any of these are missing or the conversion appears incorrect, contact your supplier. Ofgem requires licensed gas suppliers to display all conversion components on bills so customers can verify the calculation.
Frequently Asked Questions
How do I convert my gas meter reading to kWh?
Multiply the units used (in cubic metres) by the calorific value (approximately 39.5 MJ/m³), then multiply by the volume correction factor 1.02264, then divide by 3.6. For a quick estimate, multiply cubic metres by 11.2 to get approximate kWh.
How many kWh is 1 cubic metre of gas?
Approximately 11.2 kWh, based on a typical calorific value of around 39.5 MJ/m³ and the standard volume correction factor. The exact figure varies slightly depending on the calorific value applicable to your area and billing period.
Why does my gas bill show kWh when my meter shows cubic metres?
Gas meters measure volume, but energy suppliers are legally required to bill in kWh (a measure of energy) under the Gas Act 1986. The conversion from cubic metres to kWh uses the calorific value of the gas and a volume correction factor, both of which should be shown on your bill.
What is the volume correction factor for gas?
The standard volume correction factor (VCF) used in the UK is 1.02264. It adjusts the gas volume measured by the meter (at meter temperature and pressure conditions) to the standard reference conditions used for energy calculations.
