When you're decades away from retirement, saving may not be your biggest priority. With a laundry list of bills and other financial responsibilities, it may be tempting to focus more on those than retirement planning.

However, the longer you put it off, the harder it will be to catch up. Eventually, it may even become unrealistic to assume you'll be able to retire on time with as much as you're hoping to save.

Approximately 62% of workers admit that they're behind on saving for retirement, a survey from TD Ameritrade found. Yet according to the same survey, 64% of workers are also confident they'll be able to retire by age 65 or even earlier. On the surface, that may seem like a good thing that workers are so confident in their financial futures. But in reality, it may also signal that they're unaware of how much retirement actually costs.

Man sitting at a table with coins and dollar bills in front of him

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How much should you save for retirement?

Everyone will have different retirement goals, so there's no one-size-fits-all approach to how much you should save. However, retirement may be more expensive than you think.

The average person age 65 and older spends almost $46,000 per year, according to the Bureau of Labor Statistics. If you spend 20 years in retirement, that comes out to around $920,000 (not accounting for inflation costs). It's also not unrealistic to assume you'll spend longer than 20 years in retirement. Roughly a third of today's retirees will live into their 90s or beyond, the Social Security Administration found, and a longer life expectancy could potentially result in spending upward of $1 million in retirement.

Also, you may not receive as much help from Social Security as you might expect. The program is currently facing a cash shortage, and there could be benefit cuts in the next few decades if Congress doesn't figure out a solution soon. Even if benefits aren't reduced, Social Security checks are only designed to replace approximately 40% of your pre-retirement income. In other words, you'll still need a significant amount in personal savings to pay all your bills in retirement.

If you currently have little to nothing socked away for retirement, it's time to get a jump-start on saving. Every day you wait, the harder you'll have to work to catch up.

Saving for retirement when you're crunched for cash

Depending on how long you have until retirement age and how much you already have saved, you may have to save a couple hundred or a couple thousand dollars per month to reach your goal.

For example, say you're 40 years old with nothing saved for retirement, and you'd like to save $1 million by the time you turn 65. You'd need to save roughly $1,400 per month for 25 years, assuming you're earning a 7% annual rate of return on your investments. But if you had started saving at age 30, all other factors remaining the same, you'd only need to save around $600 per month.

Of course, even $600 per month is still a lot of money when you may not have much cash to spare. But you might have more than you think that you can reallocate to your retirement fund, and the best way to find out is to create a thorough budget with all of your monthly expenses. When all of your costs are mapped out in front of you, it's easier to see areas where you may unknowingly be overspending. Cut back where you can, and put the savings into your retirement fund.

If you've cut back on nonessential costs and are still struggling to come up with enough cash to meet your savings goal, see if you can reduce any of your essential expenses. For example, sealing any air leaks in windows and doors can potentially save you 10% to 20% on your heating and cooling bills, according to the Department of Energy. Or start carpooling to work a couple of times a week to save on fuel costs.

Those who are seriously behind on their savings will need to take more drastic measures to catch up. For instance, you might choose to downsize to a smaller, less expensive home, or you might move to a more affordable neighborhood. You may also cut your budget down to the bare bones, leaving nothing but the most essential costs so you can save more for retirement.

No matter how much time you have left to prepare for retirement, it's important to start saving now. Retirement may be more expensive than you think, and the longer you have to save, the easier it will be to accumulate a significant amount in savings.