About 21% of married couples and 45% of unmarried seniors rely on Social Security for 90% or more of their monthly income, according to the Social Security Administration (SSA). Living exclusively off a government paycheck might sound like a dream, but it usually doesn't work out that way when you do the math.

Here's a closer look at how much the average retiree can expect to get from Social Security and how that compares to the average retiree's expenses.

Social Security card and statement with calculator

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How far will your Social Security benefits go?

The SSA claims that Social Security was designed to replace about 40% of pre-retirement income for average earners, though it doesn't provide any information about what average earnings look like. In practice, it doesn't always cover 40% of average expenditures for most retirees.

The typical household headed by an adult 65 or older spends roughly $50,220 per year, according to the latest data from the Bureau of Labor Statistics. By comparison, the average Social Security benefit for retired workers as of October 2020 is just $1,521.59 per month, or $18,259 per year. That means it'll only cover about 36.3% of the average retiree household's expenses if only one person is claiming Social Security. 

If two individuals both claimed the average benefit, then Social Security would give them $36,518 per year, covering roughly 72.6% of their expenses, which is much better. But even in this scenario, Social Security alone wouldn't be enough.

Moreover, the above example is based on averages. If you spend more than the estimate above or your benefit is below the average listed here, it might not cover as much. And if you experience a health crisis in retirement, your costs could rise significantly and your Social Security benefits will have to stretch a lot further.

Making sure you have enough for retirement

You need to have personal savings in addition to your Social Security benefits. If your company offers a 401(k), this is a good place to start, especially if it matches some of your contributions. You may contribute up to $19,500 to a 401(k) in 2020, or $26,000 if you're 50 or older. When your company doesn't offer a 401(k), you can open an IRA and contribute up to $6,000 in 2020 or $7,000 if you're 50 or older. These contribution limits will remain the same for 2021.

Building a nest egg might require reworking your budget to free up some cash. Start with small changes like cutting back on unnecessary purchases and reducing your expenses, such as refinancing your mortgage. 

Increasing your income helps your retirement in two ways. First, it'll give you more cash now, which you can put toward retirement. And second, it'll increase your Social Security checks. Your benefits are based on your average monthly earnings over your 35 highest-earning years, with adjustments for inflation. So anything you can do to raise your income now will give you bigger checks when you do begin claiming Social Security. Try starting an extra job or negotiating a raise, though the latter might be difficult in the current economic climate. You might also consider switching fields or employers if you can find another opportunity that appeals to you.

The age you start Social Security also affects your benefits. The formula calculates your benefit at your full retirement age (FRA), which is 66 or 67 for today's workers. If you start early, you'll get less money per check. Those with an FRA of 67 who begin benefits at 62 only get 70% of their scheduled benefit, while those with an FRA of 66 who start at 62 only get 75%.

But if you delay your retirement benefits, your checks keep increasing until 70, when you get 124% of your scheduled benefit for an FRA of 67, or 132% for an FRA of 66. By waiting, however, you'll have to cover all your retirement expenses on your own until you're ready to claim Social Security.

Social Security is an important part of most people's retirement plans. By knowing how much it'll cover for you, you can calculate how much to save on your own. You can create a my Social Security account to estimate how much you might get from the program.