Many who think they know are likely off in their projections. Asked to estimate how much they needed to retire at age 65 and live for 20 years, those earning $50,000 to $75,000 annually said $250,000, at the median. Assuming inflation and annual expenses of $50,000, that amount of savings likely would run out in less than 10 years.

Six in 10 Americans have changed their behavior to offset rising gas prices, according to the survey. And 48 percent have made adjustments to deal with higher food prices. More than half of Americans, 56 percent, say they cannot save, tamping down consumer sentiment. Only 16 percent say they're financially better off now than a year ago and 29 percent say they're worse off.

All told, 9 in 10 Americans currently have financial worries, but none ranks higher than retirement. It emerged as the top issue on a list of 16 possible financial concerns facing Americans, ahead of uninsured medical expenses, the price of gas and rising education costs.

"Here's the best advice I can give for retirement planning: Start!" Amin said. "Set aside a $1 a day for an IRA, or $100 a quarter for a 401(k). It's like losing weight. Small change adds up."

That message is especially salient for younger workers. They have the biggest gap between expectations for retirement and their knowledge about preparing for it, according to the survey. Sixty percent of those aged 18 to 24 say they'll be able to retire, yet 74 percent of those in that age group have no idea how much they need to save in order to make it happen.

The National CPA Financial Literacy Commission offers these tips to help get on track for retirement:

• Track your expenses now. Most people know what they spend on the big stuff – the mortgage payment, the car payment – but they don't have a good idea where the rest of the money goes. Track your expenses for three to six months. Then think critically about how those bills might change in retirement. Less dining out, perhaps. Or more air travel.
• Create projections. A financial planner can provide the most sophisticated analysis of how much you need to save, but online calculators can help you determine, based on anticipated expenses, how long savings will last. The retirement calculator on www.360financialliteracy.org in particular, can be helpful in calculating necessary savings. Don't forget to account for inflation.
• Develop a transition plan. These days, few people turn 65 and stop working the next day. More and more, they're transitioning out of the workforce—going part time at age 65, for example, or turning a side hobby into a business that can help supplement income in retirement. If you don't quite have enough savings to let you kick back on the beach, think about part-time or consulting work that could help you transition from full-time employment to retirement.