Social Security benefits can have a major effect on your retirement, particularly if your savings aren't as robust as you'd hoped they'd be by the time you retire. But in order to make the most of your benefits, it's important to understand how the Social Security program works.

These jaw-dropping statistics can shed some light on this essential retirement program, helping you go into your golden years with as much knowledge as possible.

1. Roughly 21% of married couples rely on their benefits for at least 90% of their retirement income.

That number is even higher for unmarried beneficiaries, with nearly half of those retirees depending on their monthly checks for 90% or more of their income. The problem with that is that Social Security benefits are only designed to replace around 40% of your pre-retirement income. So if you're heading into retirement expecting that money to cover the majority of your expenses, you may be in for a rude awakening.

This is why it's extra important to ensure you have some sort of nest egg in retirement. If you have next to nothing saved and choose to retire anyway thinking that Social Security will be enough to live on, you may need to make some significant financial sacrifices to make ends meet. So if you're able, try your best to stash as much cash as you can in your retirement fund so that your benefits won't need to do all the heavy lifting.

2. Approximately 91% of older workers don't know the factors that influence their benefit amount.

Many people may not realize that they have control over how much they receive in benefits. In fact, the vast majority of workers age 50 or older don't understand all the factors that go into calculating their benefit amount, according to a survey from Nationwide. But the more you know about how your benefits are calculated, the better the decisions you can make to increase the size of your monthly checks.

Two of the biggest factors that affect your benefit amount are the number of years you've worked and the amount you earn each year. Your basic benefit amount (or the amount you'll receive if you claim at your full retirement age) is based on your 35 highest-earning working years. In a nutshell, the Social Security Administration will take an average of your earnings over those 35 years, adjust it for inflation, and come up with your benefit amount. So the higher your average is, the higher your benefit amount will be.

If you don't work a full 35 years, you'll have zeros added to your equation, thus lowering your average. But if you work more than 35 years, because only your highest-earning years are used in the calculation, you can replace some of your lower-earning years (likely from early in your career) with more recent higher-earning years. And if you pick up a side hustle or find other ways to increase your income, that can further boost your average and result in bigger monthly checks.

3. More than two-thirds (68%) of workers don't know their full retirement age.

Your full retirement age (FRA) is a vital number to know because it affects how much you'll receive each month for the rest of your life. If you claim benefits at your FRA -- which is either age 66, 66 and a few months, or 67, depending on the year you were born -- you'll receive the full benefit amount you're entitled to. You can claim before or after that age, but it will affect the size of your checks. If you claim early (as early as age 62), your benefits will be reduced. And if you wait until after your FRA to claim (up to age 70), you'll receive a bonus each month in addition to your full amount.

A whopping 68% of workers age 50 or older don't know their FRA, a Nationwide survey found. Even more concerning is that among those people, 62% think their FRA is earlier than it actually is. In other words, a lot of workers might begin claiming benefits early thinking they're going to receive their full benefit amount, when in reality their benefits will be reduced. But when you know your FRA and understand how your benefits will be affected based on the age you claim, you can ensure you're making the best decision for your situation.

4. Around 57% of workers haven't checked their estimated future benefit amount.

You don't have to wait until you begin claiming to figure out what your future benefits may look like. In fact, it only takes a few minutes to check your Social Security statements and see what you're expected to receive. And yet according to the Social Security Administration, 57% of workers who have online accounts haven't logged in to check their statements.

Checking your statements is helpful for a variety of reasons. Primarily, it helps you go into retirement more prepared. It's tough to create a retirement budget and figure out how much you can spend when you don't know how much help you'll receive from Social Security, but when you have an estimate of how much you'll be receiving in benefits each month, you can create a more thorough retirement plan. Having an idea of what your future benefit amount looks like also helps you determine how much you need to save for retirement, since your benefits alone likely won't be enough to make ends meet.

5. Roughly 78% of workers are worried that Social Security will go bankrupt.

One of the biggest worries among soon-to-be retirees is that the Social Security program will run out of money, with 78% of workers saying they share this concern, according to a Nationwide survey. However, although the Social Security Administration is facing its fair share of problems, it's not on the verge of collapse.

The truth is that the Social Security program is facing a cash shortage. With baby boomers retiring in droves and retirees living longer lifespans, the Social Security Administration is paying out more in benefits than it's receiving in taxes from workers. To fill this gap, the program tapped its trust funds -- but those funds are expected to run dry by 2035. At that point, the Social Security Administration will only have enough money to cover around 75% of expected benefits.

So what does this mean for you? First, it means the program itself is not falling apart. As long as workers continue paying their taxes, there will always be at least some money to pay out in benefits. But if Congress doesn't come up with a solution before 2035, retirees could see their benefits reduced. That's not ideal, of course, but it's not as bad as some people may think.

Social Security can be a confusing topic, and you don't need to know all the nitty-gritty details about how the program works. However, when you understand the basics of how your benefits are calculated, you'll be able to better prepare for retirement.

This article originally appeared in the Motley Fool. The Motley Fool has a disclosure policy.

RELATED STORIES