How to convert your gas meter reading to kWh

Metric gas meter

While your gas meter reading is by volume, you’re charged by kilowatt hours (kWh). Whether you have a metric or an imperial meter, find out how to convert the reading to kWh.

If you’re keen on tracking your gas usage, then you might be wondering how cubic metres (or cubic feet) of gas are converted into kilowatt hours (kWh) for the purpose of your bill.

This is often useful for those who want to keep tabs on their gas consumption, and therefore costs. It’s also useful for those who want to do an energy comparison to find the best deals, as you’ll get a handle on your usage.

Here we’ll look at how to convert cubic metres (m3) or cubic feet (ft3) of gas into kWh.

Why would I need to convert my gas meter reading?

You may not have to. Certainly if you have a smart meter, the sums and the associated cost is done for you. Likewise, the calculation will be made on your monthly bill.

However, if you want to keep track of what you’re spending and have a regular metric meter, or older imperial meter, then it’s worth taking readings, converting to kWh and working out the associated cost before waiting for your bill.

How to convert metric gas metre readings into kWh

The formula for converting cubic metres of gas to kWh is as follows:

Cubic metres (m3) x calorific value x correction factor (1.02264) ÷ kWh conversion factor (3.6) = kWh

This probably needs a little more explanation:

  • Cubic metres (m3): This is the amount of gas used. To find out how much you’ve used, take the current meter reading, and subtract the amount from your last bill.
  • Calorific value (CV): The calorific value is the amount of heat generated when a volume of gas is burned completely. Your bill should tell you your CV, which is measured in megajoules per cubic metre (MJ/m3). This will be between 37.5 and 43.0 MJ/m3.
  • Correction factor: Gas expands and contracts with changes in temperature and pressure. As such, a corrective number is factored into the calculations. The industry standard is 1.02264.
  • Conversion factor: This is the number which converts one unit to another. Here, the sum needs to be divided by 3.6 to convert it from megajoules (MJ) into kWh.

So to do this step by step, you need your meter reading, your last bill and – unless you’re a maths prodigy – a calculator.

Find out everything you need to know about meter readings.

Step 1: Subtract the previous meter reading from the new reading. This’ll give you the volume of gas used.

Step 2: Next, multiply by the volume correction factor of 1.02264.

Step 3: Now multiply by the calorific value found on your bill, which should be roughly around 40.

Step 4: Finally, divide by kWh conversion factor 3.6. This will give you your kWh used.

So let’s say your current reading is 2999.0, and the previous reading was 2880.0, meaning you’ve used 20 cubic metres.

20m3 x 40 x 1.02264 ÷ 3.6 = 227.3 kWh (to one decimal place)

How to convert imperial gas meter readings into kWh

If you have an older imperial gas meter, it’s measured in cubic feet (ft3). The process for converting this to kWh is the same as above, but you have to convert cubic feet into cubic metres first.

When you take your reading, it’s likely to be in 100 cubic feet (100ft3), where the decimal places represent cubic feet (ft3). So you can either:

  • Multiply the full number with no decimal places by 2.83; or
  • Multiply the number with decimal places by 0.0283

As such, the formula for converting imperial gas meter readings to kWh is as follows:

Hundreds of cubic feet (100ft3) x 2.83 x calorific value x correction factor (1.02264) ÷ kWh conversion factor (3.6) = kWh

So if your meter has gone up by exactly 10 since the last reading, meaning you’ve used 1,000 cubic feet:

10 x 2.83 x 40 x 1.02264 ÷ 3.6 = 321.6 kWh (to one decimal place)

Use a gas meter reading to kWh calculator

An even easier way to convert your gas meter reading to kWh is to use the Energylinx gas meter conversion calculator. Just enter your metric or imperial reading, tweak the calorific value to what it says on your bill, pop in your postcode, and you’re away.

The reason it asks for your postcode is because it also tells you how much this amount of gas should cost you, assuming you’re with your area’s cheapest gas supplier.

Want to know how much your gas appliances cost to run? Or electric appliances, for that matter? Check out our appliance cost calculator to see how long running various appliances impacts your bill.