Roth conversions have become one of the most talked-about strategies in retirement planning. The idea is simple: pay income taxes on your pre-tax retirement money now, move it into a Roth account, and never pay taxes on it again — including all the growth. But despite the enthusiasm, conversions are not a universal win. Understanding exactly when they make sense, and when they do not, can save you from a costly mistake.
Why You Might Want to Consider a Roth Conversion
The core logic behind a Roth conversion is tax arbitrage: you pay taxes at today's rate so you avoid paying taxes at a potentially higher rate later. There are several scenarios where this math genuinely works in your favor.
The first is the bracket gap window — the years between retirement and when Social Security and Required Minimum Distributions (RMDs) begin in full. If you retire at 62 and delay Social Security until 70, you may have eight years where your taxable income is artificially low. Converting in that window lets you fill up lower brackets (12% or 22%) before RMDs force you into 24% or higher.
The second driver is RMD risk. The IRS requires you to start withdrawing from traditional IRAs and 401(k)s at age 73. On a $2 million pre-tax balance growing at 7% annually, your RMD at age 73 could easily exceed $90,000 — on top of Social Security. That combination can push you deep into the 22–24% bracket even if your actual spending needs are modest. Converting a portion of that balance before RMDs begin permanently reduces the account subject to those forced withdrawals.
Third, Roth accounts have no RMDs during your lifetime, meaning the money can compound tax-free for decades and pass to heirs who then enjoy ten years of continued tax-free growth. If leaving a tax-efficient legacy matters to you, Roth accounts are hard to beat.
When the Numbers Actually Make a Case for Converting
Let's look at two concrete examples where a conversion strategy makes real sense.
Example 1 — The Early Retiree with $6 Million Pre-Tax
Imagine someone who retires at 55 with $6 million in a traditional 401(k) and an additional $400,000 in a taxable brokerage account they can use to pay taxes. At 7% annual growth, that $6 million becomes roughly $11.5 million by age 73 — and the first-year RMD on that balance would be approximately $430,000. Added to even a modest Social Security benefit, nearly all of that withdrawal would be taxed in the 32–35% federal bracket, plus state taxes where applicable.
If instead this person converts $200,000 per year from ages 55 to 72, paying the taxes from their brokerage account at a blended rate of roughly 24%, they spend about $48,000 in taxes per year — $816,000 total over 17 years. In exchange, they convert $3.4 million of future RMD-subject money into tax-free Roth dollars. The tax-free compounding on that money, combined with dramatically lower RMDs, easily justifies the upfront cost. For this person, converting is not just a good idea — it is one of the most impactful financial moves available.
Example 2 — The Still-Working High Earner with $2 Million Pre-Tax
Now consider someone who is 50, still working, earning $180,000 per year, and has $2 million in pre-tax accounts. They are already in the 24% bracket from their salary alone. Any dollar they convert today is taxed at 24% on top of their existing income — potentially at 32% once you account for the additional conversion income. Meanwhile, their $2 million balance, while meaningful, is unlikely to generate crippling RMDs. At 7% growth to age 73, that balance might reach $8.5 million — a large RMD problem — but the issue is that converting now at 32% to avoid paying 24–28% in retirement is the wrong direction.
For this person, a small Roth contribution through their workplace plan makes sense, but aggressive conversions on top of a working income do not. The better move is to keep contributing pre-tax, reduce taxable income today, and revisit the conversion question the year they retire — when income drops and the bracket gap opens up.
The Part Nobody Talks About: What That Tax Money Could Earn Instead
Here is the honest question every Roth conversion analysis has to answer: what if you just kept the tax money and invested it?
Suppose your conversion would cost you $50,000 in federal income taxes this year — a realistic number if you're converting $200,000 and you're in the 24% bracket. If you instead keep that $50,000 in a taxable brokerage account and invest it at 7% annually for 20 years, it grows to approximately $193,000. Even after paying long-term capital gains taxes on the growth, you are left with around $160,000 — real money that could have offset higher-bracket RMDs for two to three years.
This does not mean conversions are bad. It means they are only better than the alternative when the tax rate you avoid in the future is meaningfully higher than the rate you pay today. If you're converting at 24% to avoid paying 24% later, the math is roughly a wash, and paying the taxes now means you gave up $50,000 in invested capital for a decade or two before breaking even.
The break-even math shifts decisively in favor of converting when:
- Your future bracket is materially higher (e.g., converting at 12–22% to avoid 32%+)
- Your balance is large enough that RMDs will push you into top brackets regardless of other income
- You are using brokerage funds — not IRA money — to pay the conversion taxes, so the IRA itself grows undiminished
- You have a long time horizon for the Roth to compound before you or your heirs need it
The Bottom Line: Not for Everyone
Roth conversions are a genuinely powerful tool in the right hands. The early retiree with millions in pre-tax accounts and a funded brokerage to cover taxes is a near-perfect candidate. The high earner still working who would layer conversion income on top of a full salary is usually not.
Before committing to a conversion strategy, run the actual numbers for your situation. Look at what your RMDs will be at 73 based on your current balance and expected growth. Estimate your total taxable income in retirement including Social Security. Then compare the tax rate you would pay today against the rate you are likely to pay on those forced withdrawals. If there is a genuine gap — and especially if you have outside money to pay the taxes — converting makes sense. If there isn't a gap, investing that tax money and letting it compound alongside your pre-tax accounts may leave you with more after-tax wealth in the long run.
A tax professional or fee-only financial planner can help you model this with your exact numbers. The IfISaved Roth Conversion Analyzer can also run Monte Carlo projections across multiple strategies to help you see the projected outcome before making a decision.