Gas Unit Converter

Gas meters don't measure kilowatt hours - they measure the volume of gas you've burned, in cubic metres (m³) or, on older imperial meters, hundreds of cubic feet. Your supplier then converts that volume into kWh to price your bill.

This converter uses exactly the same formula that's printed on your gas bill, and shows the working at every step - so you can check your bill's conversion, or turn two meter readings into an energy figure yourself.

The gas conversion formula explained

Every gas bill in the UK converts units to kWh the same way:

• Imperial meters only: multiply the units by 2.83 to convert hundreds of cubic feet into cubic metres.

• Volume correction (x 1.02264): gas expands and contracts with temperature and pressure, so the industry applies a standard correction factor to put every meter reading on a level playing field.

• Calorific value (x 37.5 to 43): the energy content of the gas itself, in megajoules per cubic metre. It varies slightly by region and from day to day depending on the gas mix in the network.

• Divide by 3.6: converts megajoules into kilowatt hours (1 kWh = 3.6 MJ).

Metric or imperial - which meter do I have?

Look at the meter's display. Metric meters show m³ (cubic metres) and usually have a digital or five-digit display; imperial meters show ft³ (cubic feet) and are typically the older dial or four-digit models. If your meter says "cubic feet" anywhere, use the imperial setting - each unit recorded is one hundred cubic feet, which is why the conversion multiplies by 2.83 rather than 0.0283.

What is the calorific value?

The calorific value (CV) is how much energy a cubic metre of gas releases when burned. National Gas measures it daily across the network, and your supplier prints the value used for your billing period on your bill - it's almost always between 37.5 and 43 MJ/m³, with 39-40 being typical. A higher CV means each unit of gas contains more energy, so the same meter reading produces more kWh.

Why check the conversion yourself?

Two reasons. First, estimated bills: if your supplier hasn't had a real meter reading for a while, the units on your bill are a guess - converting your actual meter readings tells you what you really used. Second, comparing tariffs: gas is priced per kWh, so knowing how your units translate is the first step to knowing whether you're paying too much per unit of energy.

Frequently asked questions

Why does the correction factor never change?

1.02264 is an industry-standard figure set out in the Gas (Calculation of Thermal Energy) Regulations. It assumes average temperature and pressure conditions; unless your meter is at unusual altitude, it's the same on every bill in the country.

What calorific value should I use?

Use the one on your latest bill for the closest match. If you don't have a bill to hand, 39.5 is a reasonable typical value - across the realistic range of CVs the difference is only a few percent.

My bill says "E" next to the reading - what does that mean?

E marks an estimated reading. Submit an actual reading (or let a smart meter do it) and your next bill will be corrected - this converter will tell you what the corrected kWh figure should look like.

Does the same formula apply to business gas?

Yes - the conversion is identical. The differences for businesses are commercial: business gas is quoted per kWh at rates agreed per contract, and larger sites may be billed from half-hourly data rather than periodic readings.