The figures are in on retirement financial planning estimates, and it's not a good look for U.S. adults, most of whom are at the back of the class when it comes to estimating their long-term money needs.

That after a new report from The American College of Financial Services and its Retirement Income Literacy Survey. In it, the ACFS states that three out of four older Americans earn an F on a basic quiz on how to make their nest eggs last through retirement.

U.S. adults also grade poorly on proper Social Security planning and in underestimating how many Americans will need long-term care at some point in their lives.

Here's more from the ACFS study:

  • Only 33% understand that it is more effective to work two years longer or defer Social Security for two years than to increase retirement contributions by 3% for five years just prior to retirement.
  • Fewer than half (45%) recognize that a life annuity can protect against life expectancy risk.
  • Only 38% of participants in the survey know that 4% is the amount they can afford to "safely" withdraw per year from a retirement account.

Those are scary numbers, given the slow, steady march into retirement by the Baby Boomers, over 70 million strong.

"More and more Americans are retiring but so few understand basic facts and strategies when it comes to ensuring that their retirement is a comfortable one," says David Littell, retirement income program co-director at The American College of Financial Services. "The results of this survey are alarming and a stark reminder of the need to be prepared for the decades in retirement when you are not earning a steady stream of income."

"It's extremely hard to put a good retirement plan in place when consumers are not literate about the risks they face and how to solve for these risks," adds Jamie Hopkins, retirement income program co-director at The American College of Financial Services. "For instance, the misunderstandings about long-term care shown in the survey indicate that people don't understand the huge burden a long-term care event will have both on their finances and family."

One reason why Americans seem to fail "Retirement 101" so spectacularly is hubris - they have a misplaced sense of comfort about their own retirement savings prospects.

"Overconfidence is the main behavioral bias that impacts American's saving for retirement today," says Stephen Rischall, founding partner at 1080 Financial Group, in Sherman Oaks, Calif. "When it comes to retirement planning, overconfidence causes people to overestimate their level of preparedness and underestimate risks."

The failure of many Americans to save is the later-life equivalent of the 22-year-old who doesn't have health insurance, says Bryan Ellis, a retirement expert at

"To the 22-year-old, there's always been health, so it seems plausible that there will, somehow, always be good health for them in the future," Ellis explains. "Similarly, the unprepared retiree is a victim of the delusion that their ability to earn will never change. Unfortunately, all evidence suggests the opposite."

Additionally, U.S. adults may be either indifferent or downright anger to any direct advice on retirement savings specifics.

"I've actually experienced some initial hostility from clients when giving them my idea of a comfortable amount to retire with," says Michael Cirelli, a financial advisor at SAI Financial in Warrenville, Ill.

But that doesn't stop Cirelli from providing specific retirement savings advice - and specific savings numbers - to his clients, whether they like it or not.

"Special circumstances aside, I tell each client that they should aim to have 20 times their annual salary the year they retire," he says. "I then follow that up by saying, while 20 times is our goal, 15 times is acceptable as a minimum, but let's set the expectations high. I think it's very important to manage expectations with clients to make sure we're both on the same page and striving toward the same goals."

To slide toward an A grade on retirement savings and estimates, workers need a good old-fashioned dose of reality.

"It's time that retirement-minded American's face facts," notes Lou Cannataro, a partner at Cannataro Park Avenue Financial in New York. "They're only in control of a few of the variables that drive their financial planning and probability of success when looking to retire. The two biggest factors are how and when they plan to spend earned income during retirement."

Retirees can ease that process - and earn much-needed income - by taking a part-time job in retirement. "People realize that taking on a part-time job during retirement may provide a great pressure relief, especially in the early stages of retirement," he says. "This may deliver a strong tail wind for a successful retirement, as clients ease out of their working years lifestyle."

Getting a reality check may be the best way to up that retirement grade average, but even so, Americans have a lot of lesson work to do before passing Retirement 101 - a class that seems to be over the heads of way too many U.S. adults.

Editors' pick: Originally published May 5.