It's not a secret that millions of older Americans today rely on Social Security to some degree to make ends meet. But for some people, those benefits are their primary or only source of retirement income. And that's a bit concerning.

You might assume that Social Security pays the typical senior thousands of dollars per month. But the average benefit today may be smaller than what you'd expect.

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Social Security's average benefit today

Social Security releases a monthly snapshot that includes key program data, including the average benefit. And as of February, the typical retired worker was getting $1,980.86 per month.

When do the math, we see that amounts to around $23,800 per year. And while that's perhaps a nice amount of supplemental retirement income, it's not a lot of retirement income by itself.

And there lies the problem with assuming you can retire mostly or solely on Social Security. If you earn an average wage, you can expect your monthly benefits to replace about 40% of your pre-retirement earnings. But most seniors need more like 70% to 80% of what they used to earn in order to live comfortably.

Granted, just because the average Social Security benefit today is around $1,981 doesn't mean that's what you'll be in line for. If you're a higher earner, your monthly benefit at full retirement age could be hundreds of dollars higher.

But if you earn an above-average wage, you might get even less replacement income out of Social Security. So it's important to make sure it's not the only income stream you have to fall back on later in life.

Save well for retirement so you don't end up struggling

Although $23,800 a year in benefits isn't exactly pocket change, it's probably not a sum you want to live on annually. So instead of forcing yourself to do that, try saving for retirement while you still have time left in the workforce.

If you're 47 with no savings and expect to retire at 67, start socking away $250 a month by cutting spending or, if needed, boosting your income with a side job. If you save that monthly sum over the next 20 years and your portfolio generates an annual 8% return, which is a bit below the stock market's average, you could be sitting on a $137,000 nest egg. That's not a ton of savings, but it's something to supplement your Social Security with.

And if it's too late to save meaningfully for retirement -- say, because you're right on the cusp -- try working a few extra years so you can delay your Social Security claim past full retirement age. For each year you do, until you turn 70, your monthly benefits get to grow 8%. And while it's not ideal to live on Social Security alone in general, it's easier when your benefits are boosted.

If the average Social Security benefit today surprises you, and not in a good way, consider it a wakeup call to save for retirement as best as you can. Even if you only manage to accumulate a modest amount of savings, it could go a long way once your career comes to an end.