How to Identify Your Gas Meter Type
Before converting gas units to kWh, you need to know whether your meter measures in cubic metres (metric) or cubic feet (imperial). Using the wrong meter type in your calculation will give a result that's off by a factor of 35 — a very costly mistake on a bill dispute.
Still unsure? Check your gas bill — it will either label your meter type or show a conversion factor (0.0283168 for imperial meters). You can also call your gas supplier and they'll confirm your meter type from your account. If your meter readings on bills seem to jump by thousands between months, you almost certainly have an imperial meter.
How to Convert Gas Units to kWh: Step by Step
The process is identical for both meter types — the only difference is an extra step for imperial meters to convert cubic feet into cubic metres before the Ofgem formula can be applied.
Take Your Meter Reading
Write down your current reading from the gas meter display. For dial meters (common on older imperial meters), read each dial from left to right, noting the lower number when the pointer falls between two digits. Ignore any red dials entirely — these are tenths of a unit and not used in billing. The result is your current reading in either m³ or ft³ depending on meter type.
Calculate Units Used
Subtract your previous reading from your current reading. The result is the number of gas units consumed in the billing period. Example: current 1,250 − previous 1,230 = 20 units used. If your meter has rolled over from 9,999 back to 0, add 9,999 to the current reading before subtracting. Smart meters calculate this automatically.
Find Your Calorific Value
The calorific value (CV) is the amount of energy in each cubic metre of your gas supply. Find it in the usage breakdown section of your gas bill — look for "CV", "calorific value", or "energy content". It may be shown as MJ/m³: divide by 3.6 to get kWh/m³. 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 Correct Formula
Metric meters: kWh = m³ × CV × 1.02264 ÷ 3.6
Imperial meters: kWh = ft³ × 0.0283168 × CV × 1.02264 ÷ 3.6
The 0.0283168 converts cubic feet to cubic metres. The 1.02264 is the volume correction factor set by Ofgem. The ÷ 3.6 converts megajoules to kWh. Our calculator handles all of this automatically — just enter your readings and select your meter type above.
Check Against Your Bill and Calculate Cost
Your calculated kWh should match your bill's kWh figure closely. To work out the actual cost in pounds, multiply kWh by your unit rate (pence per kWh) and add standing charges and 5% VAT. Use our gas bill calculator to do this automatically — it accepts your kWh result directly and produces a full cost breakdown.
The Two Formulas Explained
Both formulas produce the same kWh result for the same volume of gas — the imperial formula simply adds a conversion step at the start. The 0.0283168 factor converts cubic feet to cubic metres (since 1 ft³ = 0.0283168 m³), then the standard Ofgem formula takes over. This is why a metric reading of 20 m³ and an imperial reading of 706 ft³ both equal approximately 224 kWh.
Worked Examples: Metric & Imperial
These examples show the full calculation step by step. Verify these against the calculator above to check your understanding.
= 807.28 ÷ 3.6 = 224.24 kWh
Cost at 7.42p ≈ £16.63
= 806.44 ÷ 3.6 = 224.01 kWh
Cost at 7.42p ≈ £16.62
= 3,535 ÷ 3.6 = 981.9 kWh
Cost at 7.42p ≈ £72.85
= 3,534 ÷ 3.6 = 981.6 kWh
Cost at 7.42p ≈ £72.83
Gas Units to kWh: Quick Reference Table
Use this table for quick conversions without the calculator. Based on UK average CV of 39.5 kWh/m³ and VCF of 1.02264. Green rows = metric, orange rows = imperial equivalents. For other CV values, use the calculator above.
| Units Used | Meter Type | kWh | Cost (7.42p) | Typical Usage Period |
|---|---|---|---|---|
| 1 m³ | Metric | 11.18 kWh | £0.83 | ~2 hrs heating |
| 35 ft³ | Imperial | 11.13 kWh | £0.83 | ≈ 1 m³ |
| 5 m³ | Metric | 55.92 kWh | £4.15 | ~1 day winter |
| 177 ft³ | Imperial | 56.15 kWh | £4.17 | ≈ 5 m³ |
| 20 m³ | Metric | 223.68 kWh | £16.60 | ~1 week winter |
| 706 ft³ | Imperial | 224.01 kWh | £16.62 | ≈ 20 m³ |
| 50 m³ | Metric | 559.20 kWh | £41.49 | Monthly summer |
| 1,766 ft³ | Imperial | 560.03 kWh | £41.55 | ≈ 50 m³ |
| 86 m³ | Metric | 961.83 kWh | £71.37 | UK avg monthly |
| 3,037 ft³ | Imperial | 961.6 kWh | £71.35 | UK avg monthly |
| 100 m³ | Metric | 1,118.39 kWh | £82.98 | Monthly winter |
| 3,531 ft³ | Imperial | 1,118.1 kWh | £82.96 | ≈ 100 m³ |
| 200 m³ | Metric | 2,236.79 kWh | £165.97 | ~2 winter months |
| 1,030 m³ | Metric | 11,519 kWh | £854.71 | UK avg annual |
All calculations use CV 39.5 kWh/m³, VCF 1.02264, unit rate 7.42p/kWh. Costs exclude standing charge and VAT. Use the gas bill calculator for a full cost breakdown.
UK Regional Calorific Values
Your calorific value varies by region and changes seasonally. Always use the exact CV from your gas bill for the most accurate conversion. This table shows typical ranges by area so you can verify whether your bill's CV is normal for your region.
| UK Region | CV Range (kWh/m³) | Band | 1 m³ in kWh |
|---|---|---|---|
| 🇬🇧 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 vary seasonally. Always use your bill's specific CV for exact calculations.
Gas Units to kWh: Complete UK Guide
What Is a "Gas Unit" in the UK?
A gas unit simply means one increment on your gas meter display — but what that increment represents depends on your meter type. For the approximately 80% of UK homes with a metric meter, one unit = one cubic metre (m³) of gas. For the remaining 20% (mostly older properties) with an imperial meter, one unit = one cubic foot (ft³) of gas.
Since 1 cubic metre = 35.315 cubic feet, a metric meter reading of 1,000 m³ is exactly the same volume of gas as an imperial meter reading of 35,315 ft³. Both convert to the same kWh figure when the correct formula is applied — the unit on your bill is always kWh regardless of which meter type you have. This is explained in detail in our complete guide to converting gas units.
Why Don't Gas Suppliers Just Put kWh on the Meter?
Gas meters measure volume because that's what physically passes through the pipe — it's mechanically simpler and more reliable than measuring energy directly. Converting volume to energy requires knowing the calorific value of the gas, which changes daily depending on gas source and composition. It's impractical to build this into every domestic meter. Instead, Ofgem requires suppliers to do the conversion calculation on your bill using the actual CV from your local gas distribution network for that billing period.
How Much Does 1 Gas Unit Cost in the UK?
Under Ofgem's Q1 2025 price cap, the unit rate is approximately 7.42p per kWh. Since 1 metric gas unit (1 m³) equals approximately 11.18 kWh, the cost of 1 metric unit is roughly 83p. For imperial meters, 1 unit (1 ft³) equals approximately 0.317 kWh, costing just 2.4p. Use our gas bill calculator to enter your exact unit rate from your bill and calculate your actual cost including standing charges and VAT.
Gas Units for Different UK Energy Suppliers
All UK regulated gas suppliers — British Gas, Octopus Energy, EDF, Scottish Power, E.ON, and others — use exactly the same Ofgem formula to convert your meter reading to kWh. The only thing that varies between suppliers and billing periods is the calorific value, which they must display on your bill. If you're comparing quotes between suppliers, make sure you're comparing like-for-like kWh figures rather than unit readings.
Smart Meters and Gas Units
Smart meters send automatic readings to your supplier and typically display both your raw meter reading (m³ or ft³) and a calculated kWh figure. If your smart meter shows kWh directly, there's nothing to calculate — that's already the final figure for billing. If it shows m³ or ft³, use our calculator above to convert. Note that smart meter displays refresh every 30 minutes, so readings taken at different times of day will show slightly different consumption figures.
Related Gas Conversion Tools
Once you have your kWh figure, explore these related calculators: gas m3 to kWh calculator (dedicated metric converter with regional CV table), cubic feet to kWh calculator (dedicated imperial converter), gas bill calculator UK (converts kWh to pounds including VAT), gas usage calculator (daily/monthly/annual projections), and our complete M3 to kWh conversion guide.
Frequently Asked Questions
How do I convert gas units to kWh?
Imperial meters (ft³): kWh = units × 0.0283168 × Calorific Value × 1.02264 ÷ 3.6
Or use the calculator above — select your meter type, enter current and previous readings, and get your kWh instantly. The UK average calorific value is 39.5 kWh/m³ if you don't have your bill to hand.
What is 1 unit of gas in kWh?
For imperial meters: 1 unit = 1 ft³ ≈ 0.317 kWh (at UK average CV 39.5 kWh/m³)
The exact value depends on your calorific value — see your gas bill or the regional CV table above.
Do I have an imperial or metric gas meter?
Imperial meters (older properties): display shows "ft³", "CF" or "cubic feet". Readings are typically in the tens of thousands.
If still unsure, check your gas bill — it should state your meter type, or show a conversion factor of 0.0283168 applied (confirming imperial). Your gas supplier can also confirm from your account.
How many kWh is 100 gas units?
Imperial (100 ft³): 100 × 0.0283168 × 39.5 × 1.02264 ÷ 3.6 = 31.68 kWh ≈ £2.35 at 7.42p/kWh
The vast difference is why identifying your meter type correctly is essential before calculating your bill.
Why are imperial and metric readings so different?
How do I convert gas units to kWh for British Gas?
What is the Ofgem formula for converting gas units?
Imperial: kWh = ft³ × 0.0283168 × CV × 1.02264 ÷ 3.6
Where: CV = Calorific Value (kWh/m³, typically 39.5) · 1.02264 = Volume Correction Factor (adjusts for temperature/pressure) · ÷ 3.6 = converts MJ to kWh. This formula is mandated by Ofgem for all UK gas billing.