L. Murren's answer is the simplest, and is a good rule of thumb. That said, when you retire, things change and you want to do different stuff that will likely caost you money.So, if you don't know where your money is going, find out. If there's something you'd like to do, ehow much it is in today's value, then project into the future for how long you intend to do it.If there is something you want/need to buy, get an efor that and project into the future. If you need a car, this can be very useful to eat what interval you wish to replace it. My estimates stopped at age 90.When you have that figured out (or most of it), contact a financial planner who does retirement planning as well as asset management. There's lots of them available, rates for services vary, and competencies vary. My wife and I are pleased with our financial planner, and what he has done, and we are enjoying our retirement. I wish I had found him 10+ years earlier.And, that is the key! Plan early, save and invest wisely, and ride out the roller coaster days of the markets.And always plan on living on less than what you bring home.