You might be thinking that there is a wierd and wonderful secret way that IELTS examiners calculate your score for the reading and listening section of the tests.  Well, you'd be happy to know that it is really simple and you can roughly calculate your IELTS score for listening and reading yourself. 

Below is a chart for the conversion of marks out of 40 into an IELTS score.  This chart is a guide only, because sometimes the scores change slightly depending on how difficult the exam is.  Generally speaking the conversion is as follows:

Remember, these scores can change if the exam is more difficult or easier than normal, but it is a good guide to help you mark yourself.  Later I will be giveing more information on how the writing and speaking sections are marked.  Hope this helps.