What is the calorific value of gas?

The calorific value (CV) is a measure of the energy content of gas. In the UK it typically ranges from 37.5 to 43.0 MJ/m³, with 39.5 used as a National Grid default. Your exact CV is shown on your gas bill.

Why is my gas meter in m³ but my bill in kWh?

Gas meters measure the volume of gas used, but energy is billed in kWh because the energy content of gas varies. Suppliers convert the volume to kWh using the calorific value and correction factor to ensure you are billed for actual energy delivered.

What is the correction factor for gas conversion?

The correction factor (1.02264) accounts for the effect of temperature and pressure on gas volume. It is a standard industry figure used across all UK gas bills. Your bill will confirm the exact factor used.

Gas to Electricity Unit Converter

Q: How do I convert gas m³ to kWh?

Multiply your gas usage in cubic metres by the calorific value (typically 39.5), then multiply by the correction factor (1.02264), then divide by 3.6. The result is your usage in kWh. This tool does the calculation for you.

Q: How do I convert gas ft³ to kWh?

First convert cubic feet to cubic metres by multiplying by 0.0283. Then multiply by the calorific value (typically 39.5), multiply by the correction factor (1.02264), and divide by 3.6 to get kWh.

Convert your gas meter readings from cubic metres (m³) or cubic feet (ft³) into kilowatt-hours (kWh) — the unit your bill is charged in. Enter your readings below and adjust the calorific value if your bill shows a different figure.

Tip! — To find units used, subtract your previous meter reading from your current reading. Your calorific value and correction factor are shown in the small print of your gas bill. The National Grid default of 39.5 is pre-filled.

Meter Type
Gas Used (m³)
Calorific Value (MJ/m³)
Correction Factor

Converted Result

Conversion Breakdown

Step	Calculation	Result
Run conversion to see breakdown

GUIDE

What Is a Unit of Gas and Electricity?

Understand why gas meters show m³ but bills show kWh — and what the calorific value and correction factor actually mean.

Read Guide →

How to Use the Gas Unit Converter

Step-by-Step

Select your meter type — metric (m³) for newer meters, imperial (ft³) for older ones. Check your meter face — metric meters show M or M³, imperial meters show ft or ft³.
Enter your gas used — subtract your previous meter reading from your current reading to get units consumed.
Check the calorific value — 39.5 is the National Grid default and suitable for most calculations. Your exact CV is shown in the small print of your gas bill.
Check the correction factor — 1.02264 is the standard UK industry figure. Only change this if your bill shows a different value.
Click Convert — see your result in kWh with a full step-by-step breakdown of the calculation.

Why Gas Is Measured in m³ but Billed in kWh

Your gas meter measures the volume of gas passing through it in cubic metres or cubic feet. However volume alone does not tell you how much energy was delivered — the energy content of gas varies slightly depending on its composition and the atmospheric conditions at your property. To standardise billing, suppliers convert the volume reading into kilowatt-hours using two adjustment factors: the calorific value and the correction factor.

What the Calorific Value Means

The calorific value (CV) represents the amount of heat energy released when one cubic metre of gas is burned. In the UK national grid it typically ranges from 37.5 to 43.0 MJ/m³ and is measured continuously at over 100 locations across the network. The National Grid default of 39.5 is a good working average, but your exact CV is shown on your gas bill and may differ slightly by region.

What the Correction Factor Means

The correction factor (1.02264) adjusts for the difference between the volume of gas measured at your meter under local atmospheric conditions and the volume at standard reference conditions. It is a fixed industry standard used across all UK gas meters. Your bill will confirm this figure — it very rarely differs from 1.02264 unless your property has unusual atmospheric conditions.

The Full Conversion Formula

For a metric meter: m³ × CV × 1.02264 ÷ 3.6 = kWh

For an imperial meter: ft³ × 0.0283 × CV × 1.02264 ÷ 3.6 = kWh

Using the default CV of 39.5, one cubic metre of gas equals approximately 11.19 kWh. At the April 2026 gas unit rate of 5.74p/kWh that makes each cubic metre of gas worth approximately 64p in energy cost.

Frequently Asked Questions

How do I convert gas m³ to kWh?

Multiply your m³ figure by the calorific value (typically 39.5), then by 1.02264, then divide by 3.6. Using the default CV, one m³ equals approximately 11.19 kWh. This tool does the full calculation instantly.

How do I convert gas ft³ to kWh?

First multiply your ft³ reading by 0.0283 to convert to m³, then apply the same formula: × CV × 1.02264 ÷ 3.6. This tool handles imperial meters automatically when you select ft³ from the meter type dropdown.

What calorific value should I use?

Use 39.5 as a default — it is the National Grid suggested average. For the most accurate result use the exact CV shown on your gas bill, which is typically found in the small print alongside the correction factor.

Why is my converted kWh different from my bill?

Small differences are normal and usually come down to the exact calorific value used — your supplier uses the precise daily CV for your distribution zone rather than an average. If the difference is significant check that your CV and correction factor match those shown on your bill.

Does this converter work for both gas and electricity comparison?

Yes — once you have your gas reading in kWh you can compare it directly against your electricity usage in kWh since both are now in the same unit. Use the Unit Cost Calculator to then calculate the cost of each.