Roth IRA Conversion Calculator: When Converting Makes Sense

A Roth conversion is one of the most powerful tax planning moves available — and one of the most commonly botched. The concept is simple: move money from a traditional IRA or 401(k) (where you received a tax deduction going in and will pay taxes coming out) to a Roth IRA (where you pay taxes going in and pay nothing coming out). You are prepaying taxes now to eliminate them permanently in retirement.

The question is whether that trade makes financial sense. It depends entirely on two numbers: your tax rate today and your expected tax rate in retirement. If you pay 22% now to avoid paying 32% later, the conversion is a clear win. If you pay 24% now to avoid paying 12% later, you have destroyed value. The spreadsheet models this trade-off precisely, using your specific income, tax bracket, conversion amount, and retirement projections.

The editorial position is straightforward: Roth conversions are a powerful tool for the right situations, but they are not universally beneficial. The financial industry has an incentive to recommend conversions broadly (advisors managing Roth assets earn fees on a growing tax-free account), and many online calculators are built to make conversions look favourable by ignoring the time value of paying taxes early. This calculator is designed to show you the honest maths — including the scenarios where converting is the wrong move.

Disclaimer: This calculator is provided for informational and educational purposes only. It does not constitute tax or financial advice. Roth conversions have complex tax implications that vary by individual circumstance. Consult a qualified tax professional or financial advisor before executing a conversion. SpreadsheetTemplates.info is not responsible for decisions made based on the information provided.

How a Roth Conversion Works#

When you convert traditional retirement funds to a Roth IRA, the converted amount is added to your taxable income for the year. If you convert $50,000 and your marginal federal tax rate is 22%, you owe approximately $11,000 in additional federal income tax (plus applicable state tax). That $50,000 then grows tax-free in the Roth IRA, and qualified withdrawals in retirement are entirely tax-free — no federal income tax, no state income tax (in most states), and no Required Minimum Distributions (RMDs).

The break-even question is: how long must the Roth funds grow before the tax-free withdrawals recoup the upfront tax cost? If your tax rate is the same now and in retirement, the break-even is essentially immediate — you are tax-indifferent. If your tax rate will be lower in retirement, conversion costs you money. If your tax rate will be higher in retirement, conversion saves you money. The further apart the two rates, the larger the benefit or cost.

The 2026 Tax Context#

The One Big Beautiful Bill Act (OBBBA), signed in July 2025, made the Tax Cuts and Jobs Act’s individual tax rates permanent. The 2026 federal brackets are 10%, 12%, 22%, 24%, 32%, 35%, and 37%, with the top rate applying to single filers above $640,600 and joint filers above $768,600. The standard deduction is $16,100 for singles and $32,200 for joint filers.

This permanence actually affects the Roth conversion calculus. Under the pre-OBBBA assumption that TCJA rates would expire after 2025 and revert to higher pre-2018 rates, Roth conversions at current lower rates were widely recommended as a time-limited opportunity. Now that rates are permanent, the urgency has diminished — but the strategy remains valuable for anyone who expects their retirement income to push them into a higher bracket than their current one.

What the Spreadsheet Calculates#

Inputs#

You enter your current filing status, current taxable income (before conversion), the conversion amount you are considering, your current marginal federal and state tax rates, your projected marginal federal and state tax rates in retirement, the expected annual investment return (default 7%), and the number of years until you begin withdrawing from the Roth.

Outputs#

The spreadsheet produces the tax cost of conversion (the additional federal and state taxes owed this year), the future value of the converted amount at retirement (growing tax-free in the Roth), the future value of the same amount if left in the traditional account (growing tax-deferred, then taxed at withdrawal), the break-even year (the year when the Roth’s tax-free growth overtakes the traditional account’s after-tax value), and the net lifetime benefit or cost (total Roth withdrawals minus total traditional withdrawals, after all taxes).

Three-Strategy Comparison#

The most useful output is the comparison of three approaches:

Convert everything now. The entire traditional balance is converted in one year. The tax bill is large (and may push you into a higher bracket for the conversion year), but the maximum amount begins compounding tax-free immediately.

Convert gradually over several years. Spread the conversion across 3–7 years to keep each year’s converted amount within your current bracket, avoiding the bracket bump that a large one-time conversion triggers. This is the most commonly recommended strategy and often produces the best after-tax outcome.

Do not convert. Leave funds in the traditional account and pay taxes at withdrawal in retirement. This is the correct choice if your retirement tax rate will be meaningfully lower than your current rate.

Roth Conversion Strategy Comparison#

Factor	Convert All Now	Convert Gradually (3–7 Years)	Don’t Convert
Upfront Tax Cost	Highest (may trigger bracket bump)	Moderate (stays within current bracket)	None
Tax-Free Growth Period	Longest (begins immediately for full amount)	Shorter per tranche (staggered start)	None (growth is tax-deferred, not tax-free)
RMD Obligation	Eliminated entirely	Eliminated for converted amounts	Traditional RMDs begin at age 73+
Best When	Current tax rate is much lower than expected retirement rate; large one-time income drop (job loss, sabbatical)	Current rate is moderately lower than expected retirement rate; steady income	Expected retirement rate is lower than current rate
Risk	Overpaying taxes if retirement rate turns out lower	Moderate; some years may be suboptimal	RMDs may push into higher brackets; tax rate uncertainty
Complexity	Low (one transaction)	Moderate (annual planning)	Low (do nothing)

When Roth Conversions Make the Most Sense#

Low-Income Years#

The single best time to convert is during a year when your income is temporarily low: a gap year between jobs, early retirement before Social Security and RMDs begin, a business loss year, or a sabbatical. Converting during a year when your taxable income is in the 10% or 12% bracket means you are prepaying taxes at the lowest possible rate. If your retirement income will put you in the 22% or 24% bracket, the conversion is a clear win.

This is particularly relevant for FIRE practitioners who leave traditional employment in their 30s or 40s and have a decade or more of low income before Social Security claiming age. The “Roth conversion ladder” — converting a portion of traditional IRA funds each year during this low-income window — is one of the most powerful tools in the early retirement toolkit. For more on this strategy, see our retirement savings tracker and FIRE planner.

Large Traditional Balances Facing RMDs#

If your traditional IRA and 401(k) balances are large enough that Required Minimum Distributions (starting at age 73, or 75 for those born after 1960) will push you into a higher bracket, partial Roth conversions in the years before RMDs begin can smooth your lifetime tax liability. Converting enough each year to “fill up” your current bracket without spilling into the next one is a disciplined, effective approach that the spreadsheet models explicitly.

Expected Tax Rate Increases#

If you believe tax rates will rise in the future — due to fiscal pressures, policy changes, or your own income growth — converting at today’s known rates locks in certainty. The OBBBA made current rates permanent, but “permanent” in tax law is always subject to future legislation. Converting now eliminates the risk of future rate increases on the converted funds.

Estate Planning#

Roth IRAs have no RMDs for the original owner, which means the account can grow tax-free for the owner’s entire lifetime and then be passed to beneficiaries (who do have RMD obligations, but withdrawals remain tax-free). For those who do not need the Roth funds during their own lifetime, this is one of the most effective wealth transfer tools in the tax code.

When Roth Conversions Do Not Make Sense#

Your current tax rate is higher than your expected retirement rate. If you are in the 32% bracket now and expect to be in the 22% bracket in retirement (because your income will decrease), converting at 32% to avoid paying 22% later costs you 10 percentage points per dollar converted. The spreadsheet shows this clearly as a negative lifetime benefit.

You must pay the conversion taxes from the converted funds. If you convert $50,000 and withdraw $11,000 from the same account to pay the taxes, you have only $39,000 growing in the Roth. This dramatically reduces the benefit. Ideally, conversion taxes should be paid from a separate taxable account, preserving the full converted amount in the Roth.

The conversion pushes you into a significantly higher bracket. Converting $100,000 when your income is already near the top of the 24% bracket means a large portion of the conversion is taxed at 32%. Gradual conversion across multiple years avoids this bracket bump and produces a better net outcome.

You are near retirement with a modest traditional balance. If your traditional accounts are small enough that RMDs will stay in the 12% or lower bracket, there is limited benefit to paying taxes now to avoid paying the same or lower rate later.

For modelling the tax impact of conversions within a broader tax picture, use our tax estimator spreadsheet to see how a conversion changes your overall tax liability for the year.

Download: Roth Conversion Calculator — Excel (.xlsx)

Frequently Asked Questions#

Is there a limit on how much I can convert to a Roth IRA?

No. Unlike Roth IRA contributions (limited to $7,000/$8,000 in 2026), there is no annual limit on Roth conversions. You can convert any amount from a traditional IRA or 401(k), subject only to the tax consequences. However, converting more than you can comfortably pay taxes on is unwise.

Can I undo a Roth conversion if I change my mind?

No. Since 2018, Roth conversion recharacterisations (reversals) are no longer permitted. Once you convert, the tax liability is locked in. This makes careful pre-conversion modelling essential — which is exactly what this spreadsheet provides.

How do I pay the taxes on a Roth conversion?

Ideally, from a non-retirement account (savings, taxable brokerage, or current-year income). Paying conversion taxes from the converted funds themselves reduces the amount that grows tax-free in the Roth, significantly diminishing the benefit. If you cannot pay the taxes from outside funds, convert a smaller amount.

Does a Roth conversion affect my Medicare premiums?

Potentially, yes. The income from a large Roth conversion can trigger Income-Related Monthly Adjustment Amounts (IRMAA), which increase Medicare Part B and Part D premiums for individuals earning above $106,000 (single) or $212,000 (joint). IRMAA surcharges are based on tax returns from two years prior, so a 2026 conversion would affect 2028 Medicare premiums. This is relevant for those converting during early retirement between ages 63 and 65.

Should I convert my entire traditional IRA at once?

Almost never. A large one-time conversion typically pushes a significant portion of the converted amount into a higher bracket, increasing the effective tax rate. Gradual conversion — spreading the amount over 3–7 years, filling up your current bracket each year without overflowing — almost always produces a better after-tax outcome. The spreadsheet models both approaches so you can see the difference.

What is the Roth conversion ladder for early retirees?

The Roth conversion ladder is a strategy for accessing traditional retirement funds before age 59½ without penalty. You convert a portion of your traditional IRA to a Roth IRA each year. After a 5-year seasoning period, the converted amount (not the earnings) can be withdrawn from the Roth tax-free and penalty-free at any age. By converting annually, you create a “ladder” of accessible funds that matures on a rolling 5-year cycle.

How do state taxes affect the conversion decision?

State income taxes can significantly alter the calculus. If you live in a high-tax state now but plan to retire in a no-income-tax state (Florida, Texas, Nevada, etc.), converting before you move means paying state tax on the conversion that you would avoid entirely if you waited. Conversely, if you are in a no-income-tax state now and might move to a higher-tax state, converting now locks in the state tax savings.

At what age should I start considering Roth conversions?

The optimal window for most people is between retirement (when earned income drops) and age 73 (when RMDs begin). This window — often a decade or more — provides the lowest-tax-rate years for conversion. However, younger workers in temporarily low-income years (career transitions, sabbaticals, startup years) can also benefit significantly from opportunistic conversions.