Gas meters explained

All gas meters display a single four or five digit number indicating the number of gas units you've used.

You can work out how many units you've used by subtracting your previous reading from an up-to-date one. Your supplier converts the number of gas units you've used into kilowatt hours (kWh) and displays this on your gas bill. A kWh is a measurement of energy based on how much energy one kilowatt of gas produces in an hour.

Digital metric meter

Digital metric gas meters measure gas usage in cubic meters (m3) and usually show 'M' or 'M3'.

1. Write down all the numbers before the decimal point, left to right.

Digital metric gas meters measure gas usage in cubic meters

2. Ignore any numbers after the decimal point (which may be shown in red).

Digital imperial meter

This is an older style of gas meter that measures gas in cubic feet (ft3) - it will usually show the words 'cubic feet' or the letters 'Ft'.

1. Write down the four numbers from left to right.

2. Ignore any numbers shown in red.

Dial meter

This type of gas meter shows a series of clock-style dials with numbers from zero to nine.

This type of gas meter features clock-style dials numbered from 0 to 9

1. Start with the left dial and write down the number indicated by the pointer, moving towards the right. If the pointer is between two numbers, record the lower of the two. However, if the pointer is between nine and zero, record it as nine.

2. Ignore any red dials.

We've also got practical tips on reading your electricity meter.

Finding your gas supply number

If you're switching gas suppliers and we can't locate your exact meter - if you live in a new-build property, for example - we'll ask you for your meter point reference number (MPRN), also known as an 'M' number. This is a unique number that identifies the meter at your property.

You can find your MPRN on your gas bill, not on the meter itself. If you have just moved into your home and do not have a gas bill, you can call the National Grid's meter number helpline on 0870 608 1524.

Once you've found your MPRN, compare energy prices with us and start your switch today.

Calculating gas use

Most people use more energy in the winter months for heating and lighting

Although gas meters measure the amount of gas used in hundreds of cubic feet or cubic metres, gas bills display your use in kilowatt hours (kWh). The industry standard formula for converting cubic measurements to kWh is as follows.

• Subtract your current gas meter reading from your previous reading to work out how many cubic meters or feet you have used.
• If your measure is in cubic feet, multiply by 2.83 to convert to meters.
• Multiply by 1.02264.
• Multiply by the 'calorific value' (find this on your bill, or ask your gas supplier).
• Divide by 3.6 to work out your kWh figure
• Multiply the kWh figure by your pence per kWh rate (find this on your bill, or ask your gas supplier) to give the cost of gas used.

Cut your energy bills with Which? Switch

The average saving when switching gas and electricity is £191 - compare gas and electricity tariffs now to find the best deal for you.

This figure is the average estimated annual saving for customers who applied to switch suppliers through Which? Switch between 1 January 2014 and 30th June 2014.

More on energy...

• Find our how to read your electricity meter
• Top tips to help you manage your energy bills