When you're planning for retirement, it can be a challenge to figure out exactly how much you'll need to have saved in order to live a comfortable lifestyle during your golden years. In some areas, your expenses will likely decrease -- for example, you may no longer need to have your work clothes dry-cleaned or pay for commuting costs. In other areas, though -- such as hobbies and travel -- you may be spending more.

While you can't plan with 100% accuracy how much you'll need during retirement, many workers who are planning on retiring soon underestimate how much their ideal retirement lifestyle will cost, according to a survey from The Wall Street Journal (subscription required).

Man and woman sitting on the beach in lounge chairs.

Image source: Getty Images.

Researchers asked participants to estimate what percentage of their pre-retirement salary they would need during retirement, and the answer most of them gave was roughly 70%. That's a perfectly reasonable number, but there's one problem: How much you're expecting to spend during retirement has to align with what your desired lifestyle will actually cost.

Participants were asked about the types of activities they expected to do during retirement, and then the researchers attached price tags to those activities to estimate how much people would actually be spending during retirement. When they compared those costs to the participants' income, they found that rather than spending just 70% of their pre-retirement income levels, the participants would be spending closer to 130% of their pre-retirement income if they did all the activities they said they wanted to do.

It's easy to understand how costs can get out of control once you leave the workforce. After all, retirement is essentially just a decades-long weekend. When you want to take a trip, you're not limited by the number of vacation days you have available. And you all of a sudden have all this free time during the week to pick up new (and expensive) hobbies or go out to brunch with friends every day.

When you're in the early years of retirement, it's also easy to forget that you have a limited amount of money that has to last you the rest of your life. While there's nothing wrong with splurging during retirement, it's important to make sure you're saving enough to make that a reality.

Balancing expectations and reality during retirement

When it comes to how much people actually spend during retirement compared to pre-retirement levels, it varies based on the household. While median household spending tends to drop by about 5% during the first two years of retirement, according to the Employee Benefit Research Institute, around 46% of households spent more during the first two years of retirement than they did before they left the workforce -- and 28% of households spent more than 120% of their pre-retirement spending amount during the first two years of retirement.

Also, although many families end up spending less during retirement than they did before, it could be in part due to the fact that they just don't have as much money. Among Social Security recipients, 21% of married couples and 44% of single beneficiaries depend on their benefits for at least 90% of their income, according to the Social Security Administration. And when you're trying to make ends meet with Social Security alone, you may not have a choice but to spend less than you did before you retired.

That being said, you still want to be able to enjoy retirement and do the activities you've always wanted to do. To make sure your expectations are in line with reality and that you're saving enough to live the retirement lifestyle you want, there are a few things you can do:

1. Create a retirement budget

A retirement budget is very similar to a typical household budget you may have already, except it's intended to determine how much you'll be spending once you retire. Many of these expenses will be the same or similar to what you're paying now (mortgage, utilities, car loans, etc.), but you'll also likely have new categories for travel, hobbies, or other fun things like dining out or going to the movies.

As you're creating this budget, be honest with yourself about how much you plan to spend. Don't assume that you'll only travel to visit the grandkids once a year, for example, if you know it's more likely that you'll be there every couple of months. The more accurate you are with your budget, the better idea you will have about how much you'll be spending during retirement.

Once you have your budget, add up all your expenses for the year to see exactly how much you'll likely need to live the lifestyle you're expecting. Then compare that number to what you're earning now to see what percentage of your income you'll need during retirement.

2. Determine whether your savings align with your budget

First, figure out roughly how much you'll have saved by the time you're ready to retire based on your current saving levels. You can do this by plugging your numbers into a compound interest calculator to see what your total savings will look like over time depending on how much you have saved now, the rate of return you're earning on your investments, and how much you contribute each month or year.

Then use the 4% rule to see how much you can comfortably withdraw each year. Basically, the 4% rule states that you can withdraw 4% of your savings during the first year of retirement; then for each subsequent year, you'll adjust that amount to account for inflation.

So, for example, say you're 45 years old with $50,000 saved for retirement, and you're also contributing $200 per month toward your retirement fund. Assuming you're earning a 7% annual rate of return on your investments, you'll have almost $300,000 by the time you turn 65. Using the 4% rule, that means you can safely withdraw nearly $12,000 during the first year of retirement.

3. Adjust your savings accordingly

If $12,000 per year isn't enough to cover the costs you'd outlined in your budget, you'll either need to cut back parts of your budget or increase the amount you're saving. Keep in mind, too, that you may also be entitled to Social Security benefits or a pension, so you may have more than just your personal savings to live on. However, the average Social Security beneficiary receives only around $1,300 per month, so consider whether that will be enough to meet all your needs during retirement.

There's no surefire way to ensure you'll have enough money saved to cover all the activities you want to do in retirement. Even if you plan every last detail, life happens, and you could be hit with unexpected costs that throw your entire budget out of whack. However, you're far more likely to succeed if you do have a plan in place, and the more prepared you are, the greater the chance that you'll be able to enjoy the retirement of your dreams.