How to Convert Gas M3 to kWh: Step-by-Step
Converting gas cubic metres to kilowatt hours isn't complicated once you know the formula. Every UK energy supplier — from British Gas to Octopus Energy — uses the same method mandated by Ofgem. Here's exactly how it works:
Read Your Gas Meter
Note your current reading in cubic metres. Metric meters (most installed post-1990) show a number followed by m³ or a superscript ³. Dial meters: read left to right, noting the lower number when the hand falls between two digits. Ignore red dials and digits after the decimal point. If you have an imperial meter (showing ft³ or CF), use our gas units to kWh calculator instead — it converts automatically.
Find Your Previous Reading
Locate your previous reading from your last gas bill or a note you took earlier. Subtract it from your current reading to get the volume of gas consumed in the period. Example: current 1,250 m³ − previous 1,230 m³ = 20 m³ used. If this is your first reading, your supplier will estimate based on previous occupant usage.
Find Your Calorific Value
The calorific value (CV) tells you how much energy is packed into each cubic metre of gas. Find it on your gas bill in the usage breakdown section — look for "CV", "calorific value" or "energy content". It may be shown in MJ/m³ — divide by 3.6 to convert to kWh/m³. If you can't find it, use the UK average of 39.5 kWh/m³. See the regional CV table below for typical values by area.
Apply the Ofgem Formula
Multiply the volume used by the calorific value, then multiply by 1.02264 (the volume correction factor — see below), then divide by 3.6. The division by 3.6 converts megajoules to kilowatt hours. Formula: kWh = m³ × CV × 1.02264 ÷ 3.6. Our calculator does all this instantly — just enter your readings above.
Verify Against Your Bill
Compare your calculated kWh with the figure on your gas bill. They should match closely. Minor differences come from rounding of the CV or billing period overlaps. Once you have the kWh figure, use our gas bill calculator to multiply by your unit rate (pence per kWh) and add standing charges to estimate the total cost in pounds.
The Official UK Gas M3 to kWh Formula
The formula below is the exact method set out by Ofgem in their energy billing guidelines and used universally across the UK gas industry:
Why is there a Volume Correction Factor?
Gas meters measure volume under the actual conditions at the meter — which vary with temperature and pressure. The volume correction factor (VCF) of 1.02264 adjusts the measured volume to what it would be at standard reference conditions (15°C and 1.01325 bar). This ensures consistent billing regardless of the ambient conditions at your meter. Ofgem sets this value as a national standard, so all suppliers use exactly 1.02264.
Why Do We Divide by 3.6?
The calorific value of gas is measured in megajoules per cubic metre (MJ/m³) in physics, but energy billing in the UK uses kilowatt hours. Since 1 kWh = 3.6 MJ, dividing by 3.6 converts the result from megajoules into the familiar kWh unit shown on your bill.
Worked Examples
Here are three real-world examples showing the formula in action across different usage levels:
= 807.28 ÷ 3.6 = 224.24 kWh
= 4,111.0 ÷ 3.6 = 1,141.9 kWh
= 10,271 ÷ 3.6 = 2,853.1 kWh
UK Regional Calorific Values
Your calorific value changes by region and season. The table below shows typical CV ranges across the UK. For the most accurate conversion, always use the exact CV printed on your gas bill — but this table helps you understand whether your bill's CV is normal for your area.
| Region | Typical CV Range (kWh/m³) | CV Band | 1 m³ in kWh (approx) |
|---|---|---|---|
| 🇬🇧 UK National Average | 38.5 – 40.5 | Average | 10.95 – 11.51 kWh |
| London & South East | 39.0 – 41.5 | Above Avg | 11.09 – 11.79 kWh |
| South West England | 38.8 – 41.0 | Average | 11.03 – 11.65 kWh |
| East Anglia & East Midlands | 39.0 – 40.8 | Average | 11.09 – 11.59 kWh |
| West Midlands | 38.5 – 40.5 | Average | 10.95 – 11.51 kWh |
| Yorkshire & Humber | 38.0 – 40.2 | Average | 10.80 – 11.42 kWh |
| North West England | 37.8 – 40.0 | Below Avg | 10.74 – 11.37 kWh |
| North East England | 37.5 – 39.8 | Below Avg | 10.66 – 11.31 kWh |
| Scotland (Central) | 37.5 – 40.0 | Below Avg | 10.66 – 11.37 kWh |
| Scotland (North) | 37.2 – 39.5 | Below Avg | 10.58 – 11.23 kWh |
| Wales | 38.0 – 40.2 | Average | 10.80 – 11.42 kWh |
| Northern Ireland | 38.0 – 40.0 | Average | 10.80 – 11.37 kWh |
Source: National Grid Gas Transmission · Values are approximate and change seasonally · Always use the CV from your gas bill for precise calculations
M3 to kWh Quick Reference Table
Bookmark this table for quick conversions. Based on UK standard calorific value of 39.5 kWh/m³ and VCF of 1.02264. For different CVs, use the calculator above or see our full M3 to kWh conversion guide.
| Gas Used (m³) | Energy (kWh) | Bill Cost (7.42p/kWh) | Typical Usage Period |
|---|---|---|---|
| 1 m³ | 11.18 kWh | £0.83 | ~2 hrs central heating |
| 2 m³ | 22.37 kWh | £1.66 | — |
| 5 m³ | 55.92 kWh | £4.15 | ~1 day winter usage |
| 10 m³ | 111.84 kWh | £8.30 | ~2 days winter usage |
| 20 m³ | 223.68 kWh | £16.60 | ~1 week winter heating |
| 30 m³ | 335.52 kWh | £24.89 | — |
| 50 m³ | 559.20 kWh | £41.49 | ~Monthly summer usage |
| 86 m³ | 961.83 kWh | £71.37 | UK avg monthly usage |
| 100 m³ | 1,118.39 kWh | £82.98 | ~Monthly winter usage |
| 150 m³ | 1,677.59 kWh | £124.48 | — |
| 200 m³ | 2,236.79 kWh | £165.97 | ~2 months winter |
| 300 m³ | 3,355.18 kWh | £248.95 | — |
| 500 m³ | 5,591.97 kWh | £414.92 | ~6 months usage |
| 1,030 m³ | 11,519 kWh | £854.71 | UK avg annual usage |
Based on CV 39.5, VCF 1.02264, unit rate 7.42p/kWh (Ofgem Q1 2025 price cap). Actual bill also includes standing charge (~29p/day) and 5% VAT. Use the gas bill calculator for a full breakdown.
Gas M3 to kWh: A Complete UK Guide
Why Does Your Gas Meter Read M3 but Your Bill Show kWh?
This question confuses almost every UK household seeing it for the first time. Your gas meter physically measures the volume of gas flowing through it — in cubic metres for modern metric meters or cubic feet for older imperial ones. But energy companies can't sell you volume, because the same cubic metre of gas contains different amounts of heat depending on its source, composition, temperature, and pressure.
Instead, gas is bought and sold by its energy content — kilowatt hours. The calorific value is the bridge between volume and energy: it tells you how many kWh of heat you get from burning one cubic metre of your local gas supply. Ofgem requires all UK suppliers to use the same conversion method so that no supplier can shortchange customers by using a different formula. Our complete M3 to kWh conversion guide goes deeper into this if you want the full picture.
Does British Gas Use the Same Formula?
Yes — every regulated gas supplier in Great Britain uses exactly the same Ofgem formula. British Gas, Octopus Energy, EDF, Scottish Power, E.ON, Shell Energy, Bulb (now Octopus) — they all calculate your kWh the same way: m³ × CV × 1.02264 ÷ 3.6. The only variable that differs between suppliers (and between billing periods for the same supplier) is the calorific value, which reflects the actual energy content of gas delivered in your area during that period. Your bill must, by law, state the CV used.
How to Check if Your Gas Meter is Metric or Imperial
Most gas meters installed in the UK since around 1990 are metric — they measure in cubic metres and usually have "m³" or "metric" printed on them. Imperial meters (measuring in cubic feet) are still found in some older properties and show "ft³", "CF" or "cubic feet" on the display or casing. If you're unsure, look at the numbers: metric readings tend to be in the hundreds or low thousands (e.g. 1,250 m³), while imperial readings run much higher (e.g. 48,000 ft³). For imperial meters, use our cubic feet to kWh calculator — it applies an additional conversion (1 ft³ = 0.0283168 m³) before the standard Ofgem formula.
How to Get the Most Accurate Reading
For maximum accuracy: (1) take your meter reading yourself rather than relying on supplier estimates, (2) use the exact calorific value printed on your latest gas bill — not the 39.5 average, (3) check whether your bill uses MJ/m³ or kWh/m³ for the CV, and convert if needed (divide MJ/m³ by 3.6 to get kWh/m³). If your calculated kWh still doesn't match your bill exactly, check whether your supplier used a different CV for part of the billing period — this happens when CV values are updated mid-quarter.
Related Conversions and Tools
Once you have your kWh figure, you might also need to: calculate your gas bill in pounds, check your monthly and annual gas consumption, convert between therms and kWh (useful if comparing UK with US energy costs), or convert MMBTU to m³ for commercial or industrial applications. All tools are free and use the same verified formula standards.