Retirement is not something any of us should leave to chance. Few of us are guaranteed ample income on which to live comfortably for decades in retirement, so it's up to us to make sure we're saving enough and investing it effectively.

Here's a look at some numbers that can deliver a wake-up call in case you need it. See how much of the following information surprises you.

An older man looks shocked as he takes off his glasses for a closer look.

Image source: Getty Images.

No. 1: Your retirement could last 30 years!

While many people plan for their retirement, lots of them don't appreciate just how long it could be. A man or a woman who is 65 this year can expect to live to an average age of 84 or 86.5, respectively, says the Social Security Administration (SSA). But those are just averages. The SSA also notes that "About one out of every three 65-year-olds today will live past age 90, and about one out of seven will live past age 95."

If you retire at age 65 and live until age 95, that's 30 years -- a period of time that's probably not far off from your entire working life. Many people retire around 62 these days, and some of them will live to age 100 -- those folks are looking at 38 years of retirement!

No. 2: Healthcare could cost you a whopping sum in retirement

It's not a secret that healthcare is very costly these days, even if you have Medicare. The folks at Fidelity scare us each year with their estimates of what a 65-year-old couple will spend out of pocket, on average, for healthcare in retirement. Their latest estimate: $285,000. (That excludes Medicare and long-term-care costs.) Here's a scarier estimate from HealthView Services: "The average healthy 65-year-old couple retiring this year can expect to pay $363,946 ($537,334 future value) in lifetime Medicare and supplemental insurance premiums and out-of-pocket costs." (Note that that's for a healthy couple.)

No. 3: 47% have saved less than $25,000

Most people are underprepared for retirement -- really underprepared. Fully 50% of those aged 35 to 44 have less than $25,000 saved for retirement, according to the 2019 Retirement Confidence Survey. That isn't good, but at least they have a lot of time in which to turn things around. How do those 55 and older fare? Well, check out the table below:

Amount Saved for Retirement

Ages 55 and Older

Less than $1,000

10%

$1,000 to $9,999

6%

$10,000 to $24,999

7%

$25,000 to $49,999

6%

$50,000 to $99,999

6%

$100,000 to $249,999

26%

$250,000 or more

40%

Source: 2019 Retirement Confidence Survey.

Yes, 40% of them have $250,000 or more, but $250,000 really won't go that far for many of us over 20 to 30 years of retirement. Here's hoping many of those folks have a lot more than $250,000 saved. Meanwhile, though, 23% of those 55 and up have less than $25,000 saved. Yikes!

No. 4: You may be able to accumulate $741,344

Fortunately, all is not lost. With some discipline and perhaps a little sacrifice (such as the curtailment of $5 fancy coffees each morning), you can amass a lot of money over time. That will likely involve investing in stocks -- perhaps with a focus on dividend-paying stocks.

As the table below shows, by socking away $15,000 each year and averaging an 8% annual growth rate, you can build a nest egg worth about three-quarters of a million dollars. That's much more likely to serve you well in retirement than just, say, $250,000.

Growing at 8% for

$10,000 Invested Annually

$15,000 Invested Annually

$20,000 Invested Annually

5 years

$63,359

$95,039

$126,719

10 years

$156,455

$234,682

$312,910

15 years

$293,243

$439,864

$586,486

20 years

$494,229

$741,344

$988,458

25 years

$789,544

$1.2 million

$1.6 million

30 years

$1.2 million

$1.8 million

$2.4 million

No. 5: Millions get 90% of their retirement income from Social Security

Twenty-one percent of married older Social Security beneficiaries get 90% (or more!) of their retirement income from the program, while about 45% of single ones do so. Overall, retirees report that Social Security provides about a third of retirement income.

Don't assume that that's enough, because the average monthly Social Security retirement benefit was recently just $1,475 -- about $17,700 annually. Of course, if your earnings were above average, you'll get more than that -- but still not a princely sum. For 2020, those retiring at their full retirement age can collect a maximum monthly benefit of $3,011.

If you want a shot at the best retirement possible, take time to do some retirement planning, and then save aggressively while investing effectively. Don't leave much up to chance.