We’ve written before about the number, which is the amount you’ll need for retirement and the title of a book on the subject. There is a new advertising campaign from ING on the subject, with a web site to assist in determining the number: www.ingyournumber.com. It’s an interesting calculation process, but there are others, at www.bloomberg.com and www.moneycentral.msn.com. I tried all three (and there are many others), and they produced about the same number for me. I wouldn’t rely entirely on them, but they are a good starting point for planning. Your own number is probably a moving target, and it takes into account specifics of your financial situation, such as pensions you or your spouse might receive, plans to work part-time after initial retirement, etc.