It's hard enough to decide what to wear Friday night, let alone make plans for 20, 30, or 60 years hence. But thanks to sunscreen, multi-vitamins with soy extracts, and elliptical training machines, there's a good chance you'll spend almost as many years as a "retiree" as you will dressing up as a 9-to-5er.

Exactly how do you pack for this particular trip to the future? Answer: Layers and lots of matching black clothing. But if we're talking metaphorically, when faced with a future expanse of expenses, the only way to prepare is to take your best guess about what your future finances will be like.

It doesn't take much to remove the guesswork from your future -- it's right there in your checkbook register. Today's expenses hint strongly at tomorrow's bills. To find out the tab for this half of your life, group your expenses in logical categories (job-related, kid-related, insurance-related, housing-related, retirement plan-related). The more specific you are, the fewer surprises will rear their ugly head in the future.

Next consider the future costs of being you. Some expenses will go away -- commuting costs, putting the kids through college, retirement contributions -- and others (medical, travel, toys for the grandkids) will replace them.

With a rough idea of what the future will cost, you can do some back-of-the-envelope accounting to see how far your current savings will take you. Three things can have a huge impact on your final figure: (1) how much you invest, (2) the rate of return you earn on your investments, and (3) the number of years those investments have to grow.

On the American Savings Education Council's website you can future-cast your retirement tab on a single page. The Ballpark Estimator worksheet will help you answer the big questions about your future costs, and figure out how much your retirement tab will really set you back.

When it comes to the second half of your life, you can hope that you're dressed appropriately or you can make sure you brought everything you'll need to enjoy the climate.