Can you wait until your 70th birthday?

Timing is everything when it comes to Social Security, and the calculus behind it is so complex that even financial planners have trouble.

About two-thirds of Americans get more than half their retirement income from Social Security. "It's the single most important decision about your finances," advises Dave Littell, retirement income program director at the American College in Bryn Mawr. "And we don't make it very carefully."

But that decision tree has two stark branches: when to retire from working, versus when to elect taking Social Security. Retire too young, and you may have to dip into Social Security too early. Electing Social Security benefits at 62 means you'll receive on average $1,500 a month, whereas if you wait until 70, you'll receive an average of 75 percent more money, or $2,640 a month, Littell estimates.

For most older Americans, saving for retirement is the top financial worry, according to a May Gallup poll.

And no wonder: The Social Security Commission estimates the average life expectancy for those still alive at age 65 to be 84 years old for men and 86 for women. And one in four Americans will live past 90 years old, while one in 10 will live past 95.

So can we survive on Social Security? Yes, but time it perfectly: There's now software to help. One program is called Social Security Analyzer, built by William Meyer and William Reichenstein, authors of Social Security Strategies. Meyer and Reichenstein mainly sell the software to financial advisers. However, it's also for sale to the public.

For example, Meyer and Reichenstein found that Americans who saved at least $200,000 on their own can stretch that by deferring Social Security as long as possible and taking withdrawals out of their retirement savings. That typical portfolio lasted 30 years.

For retirees with less saved, however, that calculus doesn't always work. They can be hit with a "tax torpedo." Taking Social Security benefits early adds to your total retirement money pile, and may push you into a higher bracket.

The calculations are so complex that American College started a program two years ago to train professional financial advisers on how to calculate retirement income and when their clients should claim Social Security.

Things to consider:

Before electing Social Security, spend other assets.

Work as long as possible. It pays to defer Social Security no matter what. The only time it doesn't is if you are single and your life expectancy is quite short. If for some strong reason you expect to die before age 80, claim early. If, unfortunately, you're right, you'll get more total benefits.

Maximize Social Security benefits for spouses. AARP's Social Security Benefits calculator shows that if a husband waits until 70 to begin collecting he increases his wife's benefits by 60 percent. Over the course of her life without him, that can mean tens of thousands of dollars. AARP's calculator is available at