Imagine saving to buy a new car without having any knowledge as to what the vehicle you want costs. Maybe you'd set aside $5,000 and head to the dealership, only to discover that you're short of what you need. Or perhaps -- though this is much less likely -- you'd save too much, and miss out on other ways you could have been using that money.

That's essentially how the majority of us are approaching retirement: More than 6 in 10 Americans (61%) say they don't know how much money they'll need to save in order to enjoy the retirement lifestyle they want, according to a new study from Bankrate.com.  

It's hard to hit a goal when you don't know what that goal is. Those who haven't calculated how much they'll need run a high risk of discovering late in the game that they need to either work longer than they expected, or settle for a lower standard of living in retirement.

An older couple walks on the beach

Achieving your retirement dreams takes planning. Image source: Getty Images.

What do people believe?

Millennials were the demographic least likely to know how much they would need in retirement, with 69% of those surveyed responding that they were unsure. Older Americans, however, weren't in much better shape: 56% of Generation Xers (ages 38-53), 58% of baby boomers (54-72), and 59% of those over 73 could not offer an estimate of how much they would need to have in their nest eggs.

Among the respondents who did have a number in mind, the median estimate was $650,000. Generation Xers were twice as likely as others to say they would need over $1 million.

"The key to retirement savings is to actually save for retirement. Put away at least 10% of your pay, including any employer contributions, into your retirement account and do it yesterday," said Bankrate analyst Taylor Tepper in a press release. "There are pretty sophisticated online calculators and tools that can help you estimate how much you're going to need, and you can always hire a fee-only certified financial planner if you want a little more hand holding."

You need to take action

How big a nest egg you'll need on the day you retire will depend on a host of factors. Are you planning on maintaining your current lifestyle? Or perhaps you intend to downsize, move someplace cheaper, and simplify your life. Do you plan to travel a lot? What is your health situation? And does your family have a history of exceptional longevity?

These are all things you need to consider, even though some key questions can't fully be answered. For example, you can't accurately predict how long you'll live, nor know with any certainty when and if a major medical calamity will strike.

You can, however, make some educated guesses, and, just as important, you can get help in doing your calculations. That's something more than half of Americans have done, according to Bankrate. Over a quarter (26%) have consulted a personal financial advisor about how much the should be setting aside for retirement; 21% have asked a family member or friend; 11% have used an online retirement calculator; 10% have reached out to a bank or financial institution; 8% relied on expert commentary or articles; and less than 1% used a roboadvisor.

While the Bankrate study revealed Americans to have disturbing degree of vagueness about our retirement finances, in at least one area, our cluelessness has a silver lining. When asked what proportion of their retirement needs they expect to be funded by Social Security, fully 61% said little to none. That’s way off, given that Social Security actually keeps 22.1 million Americans above the federal poverty line, with 68% of those being retired workers.

In fact, the average retired worker benefit was $1,409.91 a month as of March, according to Social Security Administration figures. That's certainly not enough to live on in most cases, but in 2014, Social Security provided more than half of the retirement income for 61% of retirees. That's far from "little to none."

Figuring out a reasonable target for your retirement savings is, of course, far easier than what comes next -- actually taking steps to save enough to get there. That can be daunting, but it's a lot less scary than getting to retirement age and realizing you've come up short.

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