We all know that to have a reasonably comfortable retirement, we'll need to save and invest for it. And if you ask folks what they think it will take, many may reply with a simple round number: $1 million. But just how much money anyone will need to have set aside by the time their career is complete will be personal to their individual circumstances. 

Financial experts generally say that to maintain your lifestyle after you stop working full time, you should aim to have enough income to replace about 80% of your pre-retirement income. For example, if you earn $100,000 a year, you should target a retirement income of $80,000.

Here's where that gets tricky: If you plan to annually withdraw 5% of your nest egg's initial level (adjusting upward a bit each year to compensate for inflation), you'll need $1.6 million in your account to get $80,000. Even if you factor in a monthly Social Security check of $2,000 -- which is about average benefit for retirees today -- you'd need a nest egg of $1.1 million to sustainably provide the remaining $56,000 at that withdrawal rate.

To be clear, very few Americans have anywhere close to that much in their retirement accounts.

Image source: Getty Images.

How many have $1 million or more put away for retirement

According to a Federal Reserve survey from a few years ago, only 3.2% of retirees had $1 million or more in their retirement accounts. 

As you look at the average and median balances of 401(k) by age, you'll see that most of us come up short of that dream goal of having $1 million saved by the time we retire. And it's well worth emphasizing that the wide differences between the median balances and the averages are the result of a relatively small number of people with enormous nest eggs skewing the averages higher. The median numbers represent the real middle -- half of people's account balances are lower, half are higher. 

Data source: Empower.

Socioeconomic factors

For those who haven't put away as much as they'd like for retirement, it often comes down to the circumstances in which they find themselves. As much as many of us would like to build a large nest egg, how much people actually save often relies on a host of factors:

• Education: The average college grad has three times as much in retirement savings as the average person with only a high school diploma.
• Income: Unsurprisingly, the higher a household's income, the more that household, on average, saves for retirement.
• Race: White households have higher retirement savings than households of other racial groups.
• Age: Up until people begin drawing down on their balances in their 60s to support themselves in retirement, those accounts tend to grow as we age, and those gains tend to accelerate over time due in part to the power of compound growth.
• Homeownership: Despite the costs of maintaining a home, homeowners generally have significantly more saved for retirement than renters.

While these factors can play roles in how much any given person is able to save for retirement, they don't tell the entire story. Plenty of high school graduates start successful businesses or earn excellent livings in other ways, and plenty of middle-class people put a focus on their futures and grow robust nest eggs over the years. These stats only offer a broad snapshot of who typically is able to build a larger-than-average retirement account.

All that said, if it doesn't look like you're going to hit the $1 million mark, it may be that you don't need to. If you enter retirement with little or no debt, live in a relatively low-cost-of-living area, and are good at living with a budget, the amount you'll require to retire comfortably and avoid outliving your savings may be much lower.