A Tricky Number: Your Own Life Expectancy

Saving for retirement is largely a matter of figuring out the slippery number of how many years you will live and accruing enough assets to live comfortably until that day arrives, plus any inheritance you want to leave behind. The National Center for Health Statistics puts the average American life expectancy at 77.8 years. But, of course, the elusive number varies by gender, race, health, genetics, lifestyle choices, and even socioeconomic status, the New York Times reports.

Many financial advisers will tell you to conservatively plan for 30 years in retirement. But Dean Foster, a professor of statistics as the University of Pennsylvania's Wharton School, contends he can predict your life expectancy using the information you enter and statistics about Americans, as does Thomas Perls, a geriatrician at the Boston University medical school who studies centenarians. Armed with the age at which you're expected to die, you can more accurately plan when to sign up for Social Security and how much you need to save.

You can also take a short Longevity Alliance online quiz that promises to tell you "your attitude toward longevity and money, along with tips and ideas to help you make sure your health and wealth match your longevity expectations." Although no numbers are involved, the seven-question survey will get you thinking about how long you might live and give you a little insight into your financial personality. But if you're looking for a retirement savings goal, you should try an online calculator.