As you prepare to retire, there are dozens of expenses to account for. How much will you spend on hobbies and other activities? What about travel? How will your daily living expenses change?

Roughly three-quarters of soon-to-be retirees say they expect their living expenses to either decrease or stay the same in retirement, according to a survey from the Nationwide Retirement Institute. While it's true that some of your expenses will decrease or be completely eliminated (you'll no longer need to spend money dry-cleaning your work clothes or buying expensive office lunches, for instance), there are a few hidden costs that could throw your entire plan out of whack if you don't prepare for them.

Fall leaves with dollars hiding under them

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1. Long-term care

Seven in 10 retirees can expect to need long-term care at some point in their lives, according to the Department of Health and Human Services, and the average person who needs long-term care will require it for around three years.

And it isn't cheap. The average semiprivate room in a nursing home costs around $6,800 per month -- or roughly $81,600 per year, according to HHS. At that rate, three years of care will cost around $244,800.

Medicare typically doesn't cover long-term care. While it will usually cover short stints in a skilled nursing facility if the care is medically necessary, it doesn't pay for custodial care -- including assistance with basic activities such as getting dressed, bathing, and eating. That means if you need long-term care, those costs will probably need to be paid out of your own pocket.

The majority of retirees will need long-term care eventually, so you should be preparing for it. If you don't think you'll be able to afford hundreds of thousands of dollars out-of-pocket, consider long-term care insurance to help shoulder some of the financial burden. The coverage is pricey (the average 55-year-old couple pays around $2,000 per year in premiums, according to the American Association for Long-Term Care Insurance), but if you end up needing several years' worth of care, it can save you thousands of dollars.

2. Other healthcare costs

The average retiree pays around $4,300 per year in out-of-pocket healthcare expenses, according to a study by the Center for Retirement Research at Boston College

While most retirees are eligible to enroll in Medicare at age 65, you're not off the hook financially. Even with Medicare coverage, you're still responsible for all premiums, deductibles, co-insurance, and co-payments. Plus, Medicare doesn't cover everything, so you may still face some out-of-pocket costs.

Original Medicare, or Parts A and B, covers hospital care and doctor visits, but it doesn't cover routine care (such as dental or vision care) or prescription drugs. Also, while most people won't pay a premium for Part A coverage, the standard monthly premium for Part B is $135.50. In addition, you'll pay a deductible for Parts A and B. If you want Part D coverage for prescription drugs, that costs extra.

You may choose to enroll in a Medicare Advantage plan instead, which can offer greater coverage, but at a steeper price. Advantage plans are offered through private Medicare-approved insurance companies, so rates will vary based on factors such as your location and how much coverage you want.

No matter what type of healthcare plan you choose in retirement, it's important to prepare for these costs somehow -- you can't rely on Medicare to cover them all.

3. Taxes on retirement account withdrawals

When you're checking up on your retirement savings, it's easy to fall into the trap of assuming the amount you have in your account is the amount you have to spend. But depending on the type of retirement account you have, Uncle Sam may take a chunk of your earnings.

If your savings are stashed in a Roth IRA, you won't need to pay taxes on withdrawals because you were already taxed on your contributions upfront. But with a 401(k) or traditional IRA, you can expect to pay income taxes on the money you withdraw in retirement.

Similar to how you were taxed in your working years, your income taxes are based on the amount you're earning. In retirement, your earnings include the amount you withdraw from your retirement accounts each year. Before you retire, it's important to understand what tax bracket you're in:

Tax Rate For Unmarried Individuals, Taxable Income Over: For Married Couples Filing Jointly, Taxable Income Over:
10% $0 $0
12% $9,700 $19,400
22% $39,475 $78,950
24% $84,200 $168,400
32% $160,725 $321,450
35% $204,100 $408,200
37% $510,300 $612,350

Source: IRS.

Retirement is an exciting -- and expensive -- milestone. Prepare for the everyday costs, but keep the major expenses in mind, too. The more prepared you are, the fewer financial surprises you'll face.