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Gas meter readings: cubic metres, cubic feet and kWh

Gas meters measure volume, but you pay for energy in kWh. Your supplier converts one into the other using a set formula, and you can check it yourself from two readings.

Updated 2 October 2026 · energy.org.uk editorial team

Who this is useful for

  • Anyone checking a gas bill against their own meter readings.
  • Homes with an older imperial meter that measures in cubic feet.

Check

What to check first

  • The units on the meter. The meter face says M³ (cubic metres) or FT³ (cubic feet). Metric meters usually show five numbers before a decimal point; imperial meters usually show four.
  • Which numbers to record. Write down the numbers before the decimal point. Ignore any numbers after it or shown in red.
  • The date. Take a photo with the date showing, so you have a record if a bill is disputed.
  • The calorific value on your bill. It measures how much energy is in the gas, in megajoules per cubic metre (MJ/m³), and varies slightly from bill to bill.

How the conversion works

GOV.UK sets out the method suppliers use:

  1. Subtract the earlier reading from the later one to get the units used.
  2. For an imperial meter, multiply by 2.83 to convert hundreds of cubic feet into cubic metres.
  3. Multiply by 1.02264, a correction for temperature and pressure set in regulations.
  4. Multiply by the calorific value from your bill.
  5. Divide by 3.6 to convert to kWh.

Example (metric meter): 100 units × 1.02264 × 39.5 ÷ 3.6 ≈ 1,122 kWh. At 6.40p per kWh, that is about £71.81 of gas, before standing charges.

The meter reading calculator does this for you, shows the working, and splits the cost if the price cap changed in between.

Do

Practical next steps

  1. Take a reading now and note the date.
  2. Find the previous actual reading on your last bill (not an estimate).
  3. Enter both in the meter reading calculator, with the calorific value from your bill if you have it.
  4. If the kWh on your bill is very different, send your supplier the reading and ask it to explain.

Take care

Important limitations

  • The calorific value varies, so a calculation with a typical figure can differ slightly from your bill.
  • If your meter was replaced between readings, the two readings cannot be subtracted.
  • Smart meters send readings automatically, but check your bill says “smart” or “actual” rather than “estimated”.

Related tools and guides

Sources

Official sources checked 2 October 2026.