Whether you’re in your 30s, 40s or 50s, it’s time to create a written retirement plan. And if you’re just five or 10 years out from retirement, it’s crucial that you do so.

At its most basic, such a plan entails estimating what your retirement expenses will be, and figuring out where the money will come from to pay those bills.

Creating a plan “can be an eye-opening experience for some people,” said Jeff Gorton, a CPA and certified financial planner, of Gorton Financial Group in Oklahoma City. “It can show people that, ‘Yes, I do have enough money for retirement,’ or, ‘No, I have to make sacrifices now.’ It helps them to make the hard choices.”

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If you don’t have a plan, you’re not alone. Just 29% of middle-income people in a recent survey said they have a written plan.

But having a plan ties in with feeling a lot more confident about the future: 70% of those with a written plan said they are confident in their future retirement, compared with 44% of those who do not have a plan, according to the telephone survey of 1,000 people with household incomes of $50,000 to $100,000, conducted for Wells Fargo by Harris Interactive.

And it’s not simply a case of wealthier people being more likely to have both money and a plan for how to spend it.

“Regardless of income, those with a plan had saved three times more toward their goal than those who didn’t have a plan,” said Laurie Nordquist, head of Wells Fargo Institutional Retirement and Trust.

Age isn’t necessarily a factor, either. Fully 34% of people in their 30s said they had a written plan. Read more about the survey: Youth beats middle age in retirement planning.

Do it yourself

You don’t have to pay a financial planner (though there’s a good argument to be made for going in for a retirement consultation if you’re 10 years or less away from retirement). “People can do this on their own and I would encourage them to,” Gorton said, though he noted that meeting with a planner provides accountability and “helps to make sure it gets done.”

A written plan may help you be a better saver; plus, it can have a big impact on how you feel in retirement. “A lot of people retire and they’re afraid of spending their money, so they hoard it,” Gorton said.

Without a written plan, you’re likely to have “a lot of anxiety about what can happen,” he added. “The written plan helps take away that anxiety. If you don’t have that written plan you can blow through your savings. Or you can spend too little, and have a retirement that’s really below what you deserve and what you worked all your life for.”

Start simple

Your first go at a plan doesn’t have to be complicated. Eventually, you’ll need to consider how you plan to invest in retirement, and you’ll have to get more detailed on precisely how much income to withdraw from which account, and when.

But, first things first: If you don’t have a written plan, start with the basics of income and expenses. The form that Gorton asks his clients to fill out is just one page, with entries for items such as rent or mortgage, car insurance and maintenance, TV service and gifts.

First record your current expenses. “Try to be very realistic and detailed in looking at your current expenses, down to pet care, yard maintenance, salons or spas, anything like that,” he said. “Americans aren't good at budgeting, but this is the first portion and it’s a critical portion of the written income plan.”

Then, make some guesses about how your current expenses will change in retirement. Don’t be surprised if your retirement expenses total about the same as what you spend now, rather than decreasing.

And keep in mind that more time on your hands can lead to higher spending. “The idea that your expenses may go up in retirement is kind of foreign to a lot of conventional planning, but that may be the case,” Gorton said.

How long do you need the income?

The income side of your written retirement plan is trickier for one reason: You have to guess when you’re going to die. You don’t want outlive your money, and it’s a lot harder to go back to work at 85 than it is at 65. Various free websites, including DeathForecast.com and Livingto100.com, can help you take a stab, so to speak, at your personal life expectancy.

“They really have to learn how to live off the income from their retirement accounts. That’s really where a plan comes into effect,” Gorton said. Don’t forget inflation, he added. “More income is going to be needed later, just to keep pace with inflation.”

While the initial document doesn’t have to be that complicated, it does require some serious thinking about your retirement goals. You have to think about what you’re going to be doing to know how much money you’ll need. And if you’re married or partnered, it’s crucial that this discussion involves both of you. Read more: Don’t leave your spouse in the money lurch.

“It is really digging into what they want their retirement to be,” Gorton said. “Do they want to travel, to spend time with the grandchildren? What are their hopes, goals, dreams, aspirations in retirement? Is leaving a legacy important or are the retirement funds solely for their needs? Some clients say, ‘I want the last check I write to bounce.’ But some want to leave a legacy.”

Read Robert Powell’s column: How to know if you have enough to retire.

Don’t forget, too, that your written plan is a “living document,” Gorton said. Review it at least once a year. Read Robert Powell: Grill your adviser about retirement income.

“It’s not rocket science,” said Roger Wohlner, a fee-only financial adviser with Asset Strategy Consultants in Arlington Heights, Ill.

Consider your annual spending needs, how much income you’ll get from Social Security (go the Social Security website to see), any pensions or annuities if you have them, and then how much you’ll need to pull from any tax-deferred and taxable investment accounts, Wohlner said.

That last piece is “the part that we plan around,” Wohlner said, including figuring out from which account to pull first. That decision, it’s true, is complicated, and beyond the scope of this story, so you’ll need to do your research.

When it comes to investment planning, consider this scenario: Say you need $100,000 and you’ll be collecting $50,000 from Social Security and other guaranteed income sources.

“We want to make sure there’s enough left to fund that $50,000 in pretty liquid accounts for whatever amount of time is comfortable for the client,” Wohlner said. “Then we build an asset allocation around that which combines their risk tolerance and need for growth.”

Keep in mind, even in retirement you’ll want three to six months’ worth of expenses in cash, for emergencies.

Wohlner said he asks his clients every time they meet: “Is your spending on track? Do you anticipate any major expenditures in the next three to 12 months? I ask a lot of questions and we make adjustments if needed,” he said.

“There are a lot of very bright, capable people out there,” Wohlner added. “A lot of my clients could do this on their own. But it depends on, ‘do you have the discipline to keep up on it and the ability to detach yourself from your own situation?’ and say, ‘Hey, I need to keep things in check and this is where I’m not doing as well I could.’”