My wife and I are about 10 years from retirement. We want to begin converting money in our individual retirement accounts to a Roth IRA, but the tax bite looks like a problem. We’re already in a higher tax bracket than we like. Any advice? When, or how, should we start converting?

Actually, starting today could make more sense than you think. As for “how,” the answer is: slowly but surely.

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My wife and I are about 10 years from retirement. We want to begin converting money in our individual retirement accounts to a Roth IRA, but the tax bite looks like a problem. We’re already in a higher tax bracket than we like. Any advice? When, or how, should we start converting?

Actually, starting today could make more sense than you think. As for “how,” the answer is: slowly but surely.

This question gives me the chance to address a common failing in retirement planning: waiting too long to begin converting a traditional IRA to a Roth IRA. (Assuming, of course, that such a move makes sense financially. More in a moment.) Yes, most IRA holders are aware that such conversions are possible. But many drag their feet. They recognize, as your question indicates, that the conversion itself is taxed; accordingly, they frequently wait—and wait—until they are in a low or lower tax bracket to begin the process.

In reality, though, and I can’t emphasize this strongly enough, “converting”—or, at the least, thinking about converting—should be part of one’s financial planning long before retirement. Certainly when you’re in your 40s or 50s.

“It is never too soon to be doing Roth conversions, depending on the long-term price tag: the taxes now versus taxes in the future,” says Ed Slott, an IRA expert in Rockville Centre, N.Y.

A few basics: A traditional IRA or 401(k) typically is built with pretax dollars; when you begin tapping that account in retirement, you pay tax on the withdrawals. A Roth, by contrast, is built with after-tax money, and withdrawals generally are tax-free. Deciding whether to convert the former to the latter depends on your particular tax outlook. If you estimate that you’ll pay less tax on the money you’re converting today than you would on withdrawals from your retirement savings in later life, converting probably makes sense.

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For many people, that moment arrives in the years immediately after they retire from their full-time job and before required minimum distributions from tax-deferred retirement accounts kick in at age 72. In this period, your taxable income could well be lower than when you were working; much or most of the money you need to meet expenses might come from nonretirement savings and/or Social Security. All of which could put you in a low tax bracket—and, as such, put you in place for Roth conversions.

And all that makes sense; it’s a fine strategy. But—and this is key—it isn’t the only way, and shouldn’t be the only time, to think about Roth conversions. Consider:

Small can be good

You state that you’re currently in a high tax bracket and worry about the tax bill from a conversion. That’s understandable: A large Roth conversion could push you into an even higher tax bracket.

But therein lies the problem. People tend to think about converting big chunks of money, when small amounts, converted over many years, can be equally effective. And small conversions might not push you into a higher tax bracket.

Indeed, “for those in their 40s and 50s, Roth conversions have a double benefit,” Mr. Slott says. First, tax rates today are low, by historical standards, which makes it a good time to convert. And second, you can watch your Roth dollars grow tax-free for decades.

In short, don’t think about Roth conversions as something you need to pack into an abbreviated time span. “Moderation over several years is the best approach for most,” Mr. Slott says.

Worst-case scenario, Part One

. Let’s say a Roth conversion does, in fact, push you into a higher tax bracket. It won’t be the end of the world. Again, think long term.

“If a person in their 40s or 50s is already being taxed at the top rates, it’s likely they’ll stay that way,” Mr. Slott says, “and their tax rates in retirement will be even higher, costing them more in later life.” Which could argue for a steady series of Roth conversions starting now.

“Again, it’s all about the tax rates and not so much about your age,” Mr. Slott says.

Worst-case scenario, Part Two

. Let’s say you take your time and convert gradually to a Roth, betting that tax rates will increase in the future. And let’s say you lose the bet: Tax rates, as it turns out, don’t rise—or even go lower. As such, you kick yourself for paying and wasting (in all probability) thousands of dollars in taxes on conversions that, in hindsight, you shouldn’t have made.

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But…that’s only half the story, Mr. Slott says. Let’s say you don’t convert. Sure, you look smart because you aren’t paying all of those conversion taxes in, say, your 40s or 50s. But that doesn’t mean the taxes have gone away. The tax bill is merely deferred; you begin paying it (again, if you don’t convert) at age 72, when required minimum distributions from traditional retirement accounts begin.

In short, don’t be too quick to kick yourself. Says Mr. Slott: “It’s not a question of if you’ll pay taxes, but when.”

Diversity in taxes

Most people understand the importance of diversifying their investments, but it’s equally important to diversify your tax risks.

“You don’t want to have all your retirement funds in one taxable basket,” Mr. Slott says. “Having at least some funds—consistently, over time—going into Roth accounts is an effective and simple hedge against possible future tax-rate increases.”

A final note: Again, Roth conversions aren’t for everyone. For instance, you should be able to pay the tax on the conversion with money from outside your traditional IRA. If not, you’re shortchanging yourself; you’re taking money that could have been converted and, instead, handing it to the Internal Revenue Service. Not good.

That said, if we’re focusing on taxes, many of us, I think, will see higher taxes in the years ahead. (Fixing the shaky finances at Social Security and Medicare alone will come with a sizable price tag.) And if that’s the case, making “Roth planning” a part of your finances, as early as possible, would be a wise step.

Mr. Ruffenach is a former reporter and editor for The Wall Street Journal. Ask Encore looks at financial issues for those thinking about, planning and living their retirement. Send questions and comments to askencore@wsj.com.