How much do I need to retire?

The big question for all early retirement aspirants is, "How much do I need to retire?".  I know this is a critical and difficult question to answer, since there are several discussions around this very thought in blogs and personal finance websites.  I realise that the final amount that one comes up with is very dependent on your personal situation, monthly spending assumptions, risk taking ability etc.  However, I am sure there is a common thread that you can find in the following thought process no matter where you are from. 

I am going to start with the assumption that I will require ERU1000 to be able to retire early (with some adjustments and frugality in my lifetsyle)  I will also set myself a stretch goal of ERU2000, which is twice my basic target.  This is to ensure that I am focusing on a larger goal, which should help me reach my basic target with more certainity, and hopefully earlier as well. 

To provide some perspective, my wife's and my current combined take home income is ERU7.34.  This means that my baseline target for overall retirement savings/investments is ~11.3 times my annual take home pay.  My stretch goal would amount to ~22.6 times my annual take home pay.  I will try to add some detail on how I arrived at these numbers the next time, but as of now, I think the stretch goal is practically impossible to achieve!  The baseline target sounds more realistic, but I will have to come up with a detailed plan on how to reach this goal. 

Let me know what your thoughts are regarding a safe retirement corpus?  What multiple of your annual take home pay do you need to have saved up, to be ready to retire?