As you think ahead to retirement, you most likely envision Social Security as an important support source. And, indeed, many retirees do end up relying on these government benefits to provide a large part of their take-home earnings. 

But while you can count on Social Security to be there for you throughout your retirement, you shouldn't expect to be able to live on these benefits alone. There are three important reasons why. 

Adult reviewing financial paperwork.

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1. Benefits are only designed to replace 40% of preretirement income

The single biggest reason you can't live on Social Security alone is that you aren't meant to.

See, there's a Social Security benefits formula that determines the amount of money you'll receive. It's based on average earnings in your 35 highest-earning years. You get benefits equal to a percentage of those earnings. Based on the way the formula is designed, you're supposed to get around 40% of what you were earning before retirement.

Of course, this means that if you tried to rely solely on Social Security, you'd end up taking a 60% pay cut upon leaving the workforce. The simple fact is, even in retirement, most people can't survive on just 40% of what they're used to bringing home because the necessities cost more than that amount. 

2. Cost of living adjustments aren't keeping pace with inflation

Another big problem with trying to live on Social Security alone is that you'll end up really struggling in late retirement.

That's because the value of benefits is eroding each year. This is happening because cost of living adjustments (COLAs) aren't doing their jobs. COLAs are meant to ensure benefits keep pace with inflation, but they haven't done that. Benefits have lost about 30% of their buying power since 2000.

In 2022, retirees are on track for the largest COLA in four decades. Seniors will be getting a 5.9% benefits bump. But, even this may be below the actual rate of inflation they experience, so retirees may fall further behind even after getting the most generous raise in years. 

If you're counting solely on your benefits and their buying power erodes year after year, by the time you get to the end of your retirement, your quality of life is going to be much lower than when you started. 

3. You may need to retire before you want to claim benefits 

Finally, the last big issue is that you may end up having to retire earlier than you want to claim benefits. 

While Social Security checks become available at 62, there's a chance you could be forced out of the workforce before then due to a lack of work opportunities available to older Americans or because of health or family issues. If you have to retire before you become eligible for Social Security, you're going to need some money to survive. 

Even if you can make it to 62 to retire, you may still not want to claim benefits immediately upon leaving the workforce. That's because benefits increase for each year you wait to start them up until you turn 70. And a small majority of seniors end up with more lifetime Social Security income by waiting until 70 to get their first check.

Very few people can delay leaving the workforce until age 70 or later. So if you want to max out your benefits, you may need money to live on after you stop getting paychecks while you wait to claim Social Security. 

For all of these reasons, it's important you have plenty of money saved so you can have a comfortable retirement and make decisions about Social Security benefits that best set you up for long-term financial success.