What is the calorific value of gas?

The calorific value (CV) measures the heat content of gas. In the UK, the typical calorific value for natural gas is 39.2 megajoules per cubic metre (MJ/m³), though it varies slightly by region and season, typically between 37.5 and 43.0 MJ/m³. Your gas supplier uses the CV as measured at your local network distribution point and prints it on your bill.

What is the correction factor used in gas calculations?

The correction factor (1.02264) adjusts for the difference between the temperature and pressure at which the gas is measured by your meter (ambient conditions) and the standard reference conditions (15°C, 1.01325 bar). This is an Ofgem-standard value used consistently across UK gas bills.

How much does gas cost per kWh in the UK?

Under the Ofgem price cap (October 2025 quarter), the gas unit rate is approximately 6.24p per kWh for a typical household on a direct debit tariff (the "typical" rate, your actual rate may vary by region, supplier, and tariff). There is also a standing charge of approximately 31p/day. Check your bill for your exact rate.

How do I read my gas meter?

For a metric meter, read the black digits (ignoring the red digits). For an imperial meter, read the first four digits. Note the reading and the date. Your usage is the difference between two readings in m³ (metric) or ft³ (imperial). This calculator converts either unit to kWh using the Ofgem standard formula.

Why does my gas bill show different kWh from my meter?

Your meter measures volume (m³ or ft³), not energy. The kWh figure on your bill is calculated by your supplier using the volume, calorific value, and correction factor formula. Small differences can occur if your supplier uses a slightly different CV from the one in this calculator, always refer to your bill for the exact CV used.

Updated 1 May 2026

Gas Rate Calculator · Free UK kWh Converter 2026

Convert your gas meter reading (m³ or ft³) to kWh and calculate the cost, using the Ofgem standard formula with calorific value and correction factor.

✓ Free to use✓ Metric & imperial meters✓ Ofgem methodology✓ Instant calculation

Gas Rate Calculator

Enter your meter reading and unit rate. KWh and cost appears instantly

Gas used (m³)

m³

Calorific value (MJ/m³)

Unit rate (p/kWh)

Gas usage

1113.5 kWh

Cost: £69.48 at 6.24p/kWh

Volume (m³)

100 m³

Calorific value

39.2 MJ/m³

Correction factor

1.02264

kWh conversion

÷ 3.6 (MJ → kWh)

Total kWh

1113.54 kWh

Unit rate

6.24p/kWh

Cost (excl. standing charge)

£69.48

Uses Ofgem standard conversion formula. Calorific value varies by region and season, use the value on your gas bill for precise calculations. Standing charges are excluded.

How to Calculate Gas Usage in kWh

Quick Answer: Gas meters measure volume, not energy. To convert m³ to kWh: multiply by the calorific value (39.2 MJ/m³) × correction factor (1.02264) ÷ 3.6. For imperial ft³: multiply by 0.0283168 first to convert to m³, then apply the same formula.

The Ofgem Conversion Formula

Ofgem prescribes a standard methodology for converting gas volume to energy (kWh). This is used by all UK gas suppliers on bills. The formula uses the calorific value of gas (measuring the heat content per m³) and a correction factor for temperature and pressure.

Formula

kWh = m³ × calorific value (39.2) × correction factor (1.02264) ÷ 3.6

e.g. 100 m³ × 39.2 × 1.02264 ÷ 3.6 = 1,113 kWh

Worked Example: 100 m³ used at 6.24p/kWh

Volume used100 m³

× Calorific value (39.2 MJ/m³)3,920

× Correction factor (1.02264)4,008.75

÷ 3.6 (to convert MJ to kWh)1,113.5 kWh

× Unit rate (6.24p/kWh)£69.48

Plus standing chargeSeparate

Your bill's calorific value may differ slightly from 39.2, use the CV on your bill for precise calculations.

Frequently Asked Questions

To convert a metric gas meter reading (m³) to kWh, use the Ofgem formula: kWh = m³ × calorific value (typically 39.2 MJ/m³) × correction factor (1.02264) ÷ 3.6. For an imperial meter (ft³), first convert to m³ by multiplying by 0.0283168, then apply the same formula. Your energy bill should show the calorific value used by your supplier.