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Enter the units from your gas meter below and instantly see the kWh equivalent using the official UK supplier formula. Works for both metric (m³) and imperial (cu ft) meters.
Correction Factor
1.02264
Calorific Value
39.5 MJ/m³
MJ to kWh
÷ 3.6
cu ft to m³
× 2.83
Quick fill:
Important: Please rely on a professional, accredited Gas Safe engineer and accredited tools for all measuring. This calculator provides estimates only and accepts no liability for calculations.
All UK energy suppliers use the same official formula to convert the volume of gas measured at your meter into kilowatt hours (kWh) for billing. The formula accounts for temperature, pressure, and the energy content of the gas.
kWh = Units (m³)
× Volume Correction (1.02264)
× Calorific Value (39.5 MJ/m³)
÷ 3.6
kWh = Units (cu ft)
× 2.83 (convert to m³)
× Volume Correction (1.02264)
× Calorific Value (39.5 MJ/m³)
÷ 3.6
Convert 100 m³ of gas to kWh:
100 m³ × 1.02264 = 102.264 (corrected volume)
102.264 × 39.5 = 4,039.43 MJ (energy content)
4,039.43 ÷ 3.6 = 1,122.06 kWh
So 100 cubic metres of gas is approximately 1,122 kWh of energy, which at the current Ofgem rate of 6.24p/kWh would cost around £70.02.
The gas-to-kWh conversion uses four key constants. Here is what each one represents and why it is used in the formula.
Adjusts the measured gas volume to standard conditions of temperature (15°C) and pressure (1013.25 millibar). Gas expands when warm and contracts when cold, so this factor ensures you are billed for a consistent energy quantity regardless of the weather.
The energy content of natural gas, measured in megajoules per cubic metre. This value is set by Ofgem and published by your gas transporter. It typically ranges from 37.5 to 43.0 MJ/m³, with 39.5 being the standard average used for estimates.
Converts megajoules to kilowatt hours. One kilowatt hour equals exactly 3.6 megajoules. Dividing the energy content in MJ by 3.6 gives the equivalent in kWh, which is the standard billing unit on UK energy bills.
Converts cubic feet to cubic metres. This factor is only used for imperial gas meters. One cubic metre equals approximately 35.3147 cubic feet, so one cubic foot is approximately 0.0283 m³. The rounded multiplier of 2.83 is used by UK suppliers when converting 100 cu ft to m³.
Common gas unit amounts converted to kWh for both metric and imperial meters, using the standard formula (1.02264 × 39.5 ÷ 3.6).
| Units | Metric (m³) → kWh | Imperial (cu ft) → kWh |
|---|---|---|
| 1 | 11.22 kWh | 31.75 kWh |
| 5 | 56.10 kWh | 158.77 kWh |
| 10 | 112.21 kWh | 317.54 kWh |
| 25 | 280.52 kWh | 793.86 kWh |
| 50 | 561.03 kWh | 1,587.72 kWh |
| 100 | 1,122.06 kWh | 3,175.44 kWh |
| 250 | 2,805.16 kWh | 7,938.60 kWh |
| 500 | 5,610.32 kWh | 15,877.20 kWh |
| 1,000 | 11,220.63 kWh | 31,754.39 kWh |
Calculations use standard calorific value of 39.5 MJ/m³ and volume correction factor of 1.02264. Actual values may differ slightly based on your region's published calorific value.
You might wonder why your gas bill shows kilowatt hours rather than the cubic metres or cubic feet displayed on your meter. There are four key reasons:
Your gas meter is a mechanical or digital device that measures the volume of gas flowing through it. It counts cubic metres (metric) or cubic feet (imperial) but has no way of measuring the energy content of that gas directly.
The same amount of energy can occupy different volumes depending on temperature and atmospheric pressure. Gas expands in warm weather and contracts in cold weather. Without correction, customers in warmer conditions would appear to use more gas than those in cooler conditions for the same energy consumption.
The kilowatt hour (kWh) is the standard unit of energy used across the UK energy market. By converting gas volumes to kWh, both gas and electricity can be compared on the same basis. This makes it easier to compare tariffs, switch suppliers, and understand your total energy costs.
The conversion process — applying the volume correction factor and calorific value — ensures you are billed for the actual energy delivered to your home, not just the raw volume. This is regulated by Ofgem to protect consumers and ensure fair, transparent billing.
Not sure which type of gas meter you have? Here is how to tell the difference between metric and imperial meters, which affects how your gas units are converted to kWh.
If you are still unsure, check your latest gas bill — it will state whether your meter reads in m³ or cu ft. You can also contact your supplier or check the meter label. For help understanding your bill, visit Citizens Advice.