The long, explained answer;

Since your meter appears to measure in **m�** (metres cubed), we don�t have to worry about converting to metric, however, we do need to convert it to a * standardised volume*. (

*Volume varies with pressure so before any calculations are done, the actual volume you have used is converted to the gas company's standardised volume unit.)*This is the

**Volume Conversion Factor**shown on your bill.

We now need to work out how much

**energy**was in the gas you have used. This energy is released when you burn it and is known as the

**calorific value**. The SI unit of energy is the

**Joule**, and the calorific value given on your bill is measured in Mega Joules per metre cubed of gas. (1 Mega Joule (MJ) = 1 000 000 Joules.

The gas company works out the average calorific value over the period you have used it, (

*since it can, and does vary*).

They will give you a figure for the average calorific value on your bill. This figure will probably be around

**38 � 40 MJ per m�**.

So, now multiply your

*converted*volume of gas used (in m�) by the

*calorific value*given on your bill to get the absolute amount of energy contained in the gas you have used (in MJ).

[cont...]