Roth Conversion Tax Calculator: Should You Convert Your IRA?

How a Roth Conversion Works: The Tax Mechanics

A Roth conversion is the act of moving money from a traditional IRA, SEP IRA, SIMPLE IRA, or 401(k) into a Roth IRA. The IRS treats the converted amount as ordinary income in the tax year of the conversion, reported on Form 1040 via Form 8606. You pay tax at your marginal rate, and in return the money enters the Roth permanently — growing tax-free and leaving the account tax-free when you take qualified distributions.

Unlike direct Roth contributions, there is no income ceiling on conversions. A surgeon earning $800,000 a year can still convert $100,000 from a traditional IRA to a Roth in the same year, paying tax at the 37% rate if that is where the income lands. The question is not whether you can convert — it is whether the math makes sense given your current and projected future tax rates.

The conversion is irreversible. Prior to 2018, taxpayers could "recharacterize" — undo a conversion if markets dropped after the conversion date. The Tax Cuts and Jobs Act permanently eliminated that option. Converting and watching the assets fall in value is a real risk, which is why timing conversions to market downturns can be advantageous: you pay tax on a lower value, and the recovery happens inside the tax-free Roth environment.

The 2026 Bracket-Filling Strategy: Step by Step

The core Roth conversion strategy for most taxpayers is bracket-filling: calculate how much room you have until the top of your current tax bracket, then convert exactly that amount. Here are the 2026 ordinary income tax brackets you are filling:

Example calculation: Maria files jointly. Her combined Social Security, pension, and investment income produces $140,000 in taxable income after the $32,200 standard deduction. She is in the 22% bracket. The top of the 22% bracket for MFJ filers is $211,400. That means she has $211,400 - $140,000 = $71,400 of room before hitting the 24% bracket. Converting $71,400 costs her $71,400 x 22% = $15,708 in federal income tax, paid from outside funds if possible to maximize the Roth balance. She moves $71,400 permanently into the tax-free Roth environment.

Crucially, she does not convert $100,000 and spill $28,600 into the 24% bracket unless she has a specific reason to accept the higher rate. The strategy is surgical: fill the bracket, stop at the ceiling. Use our Income Tax Calculator to find your current taxable income before running the conversion math.

When Does a Roth Conversion Make Financial Sense?

The decision reduces to a single question: will you pay a higher tax rate on this money now, or later? If your current rate is lower than your expected future rate, conversion wins. The tricky part is that "future rate" is not just your future marginal bracket — it includes Social Security taxation, RMD-forced income, and the death of a spouse.

The most common planning window is the gap between retirement and RMD age. During those years, earned income may drop while required distributions have not yet begun, creating a temporary low-income trough where conversions can be taxed at 10%, 12%, or 22% instead of later RMD-driven rates.

Scenarios Where Conversion Is Clearly Favorable

• You are in the 12% bracket now and expect to be in the 22% or higher bracket in retirement due to large RMDs from a growing IRA.
• Your IRA is substantial. Per IRS actuarial tables, a $1 million IRA at age 73 requires an RMD of roughly $36,900 in year one — stacked on top of Social Security and any pension, this easily pushes couples into the 22-24% bracket.
• You have a surviving spouse concern. A married couple may be in the 22% bracket together, but when one spouse dies, the survivor files single at much higher rates. Conversions while both spouses are alive at lower joint rates are a well-established planning strategy.
• You inherited a traditional IRA. Non-spouse beneficiaries must empty the account within 10 years under the SECURE Act. Converting to a Roth during low-income years within that window reduces the tax hit.
• You want to reduce future RMDs. Roth IRAs have no required minimum distributions during the original owner's lifetime. Converting reduces the size of your traditional IRA and therefore reduces future mandatory taxable distributions.

Scenarios Where Conversion Is Questionable

• You are currently in the 37% bracket and expect a lower rate in retirement — deferral wins.
• You would need to liquidate the converted funds to pay the tax bill, shrinking the Roth balance significantly.
• You are in a high-tax state now but plan to retire in a no-income-tax state — conversion today means paying state tax on income you would otherwise avoid entirely.
• You are close to a Medicare IRMAA threshold and a conversion would trigger Part B and Part D surcharges that outweigh the bracket arbitrage.

IRMAA: The Hidden Conversion Trap for Medicare Recipients

IRMAA — the Income-Related Monthly Adjustment Amount — is an additional Medicare Part B and Part D premium imposed on high-income beneficiaries. The surcharge is based on your Modified Adjusted Gross Income from two years prior. A large Roth conversion in 2026 affects your Medicare premiums in 2028.

For 2026 Medicare, IRMAA surcharges begin when MAGI exceeds $109,000 for individual returns and $218,000 for joint returns. The first 2026 tier adds $81.20 per month for Part B and $14.50 per month for Part D per person. For a couple where both spouses have Part B and Part D, crossing that first cliff can add about $2,297 per year, before considering higher tiers.

The solution is to convert up to — but not across — the IRMAA threshold if Medicare premiums are part of your objective. If you are single with $90,000 in MAGI and the first 2026 cliff is above $109,000, you can convert about $19,000 without triggering that first surcharge, assuming no other income spikes.

The 5-Year Rule: What You Must Know Before Converting

Roth IRAs are governed by two separate 5-year clocks, and confusing them is one of the most common planning mistakes. The first clock applies to the account itself: you must have had any Roth IRA open for at least 5 years before qualified withdrawals of earnings are tax-free. The second clock applies to each conversion separately.

Under the ordering rules of IRS Publication 590-B, converted amounts are withdrawn before Roth earnings. Each conversion dollar is subject to a 10% early withdrawal penalty if you access it within 5 years of the conversion — unless you are age 59½ or older at the time of withdrawal. This means a 56-year-old who converts $50,000 in 2026 cannot access those specific dollars penalty-free until 2031.

For retirees over 59½, this rule is irrelevant — the 10% penalty no longer applies. But for pre-retirement conversions, particularly those using the "Roth conversion ladder" strategy to fund early retirement withdrawals, the 5-year rule must be tracked separately for every conversion year. Pair your conversion strategy with our complete Roth IRA tax guide to understand both clocks in detail.

2026 Changes: Mandatory Roth Catch-Up Contributions

Beginning January 1, 2026, SECURE 2.0 Act Section 603 takes effect: employees who are age 50 or older and earned more than the applicable Roth catch-up wage threshold from the same employer in the prior calendar year must make any 401(k), 403(b), or governmental 457(b) catch-up contributions as Roth catch-up contributions — not pre-tax. IRS Notice 2025-67 sets the threshold used for 2026 catch-up treatment at $150,000 of 2025 wages.

In practical terms, if you exceeded the 2025 wage threshold and want to make the age-50+ catch-up contribution to your employer plan in 2026, that catch-up must go into a designated Roth account within the plan if the rule applies to your plan type. You lose the immediate pre-tax deduction on the catch-up dollars, but they can grow and distribute tax-free when Roth distribution rules are satisfied. The mandatory Roth catch-up effectively forces higher-earning employees into a conversion-like decision each year.

Full Conversion Example: Maria's Optimal 2026 Strategy

Let us finish Maria's full calculation. Here is her 2026 income picture:

Maria has $171,500 of room in her 22% bracket. But she needs to check IRMAA. Her MAGI before conversion is approximately $72,100. Adding a $100,000 conversion brings her MAGI to $172,100, still below the $218,000 MFJ IRMAA threshold. If her goal is to protect the first IRMAA tier, the IRMAA cliff, not the tax bracket, caps the practical conversion near $145,900.

Decision: Maria converts $100,000 this year and plans to convert additional amounts over the next 4-5 years before RMDs begin at age 73. Her projected 12-year RMD from the $680,000 IRA (assuming 6% annual growth) would be approximately $65,000 per year — stacked on Social Security and the pension, this would put her firmly in the 32% bracket. Each dollar converted now at 22% instead saves 10 cents in future marginal tax. Over $100,000, that is $10,000 in lifetime tax savings on that tranche alone.

Paying the Tax: Inside vs Outside the IRA

One of the most consequential decisions in a Roth conversion is where the tax money comes from. If you convert $60,000 and pay the resulting $13,200 tax bill (at 22%) by withholding from the conversion itself, only $46,800 enters the Roth. If you pay the $13,200 from a taxable brokerage account or savings, the full $60,000 goes into the Roth.

The math strongly favors paying from outside funds. The $13,200 paid from savings is effectively a post-tax contribution to the Roth — it funds the tax shield on $60,000 of future tax-free growth. Paying from the IRA itself reduces the converted balance and defeats much of the long-term benefit. Never withhold federal tax from the conversion if you have outside funds available to cover the bill.

If you convert in the latter part of the year and the conversion is large, consider making a fourth-quarter estimated tax payment to the IRS to avoid underpayment penalties. Use our estimated tax payment guide to calculate the safe harbor amount.

How Roth Conversions Reduce Required Minimum Distributions

Required minimum distributions (RMDs) begin at age 73 (age 75 for those born in 1960 or later, under SECURE 2.0). The RMD amount is calculated by dividing your prior December 31 IRA balance by an IRS life expectancy factor. A $1,500,000 IRA at age 73 requires an RMD of approximately $56,000 using the Uniform Lifetime Table factor of 26.5. By age 78, the same balance (assuming 6% growth) generates an RMD exceeding $80,000.

Converting $100,000 per year for 5 years before age 73 reduces the IRA by $500,000 — cutting the first-year RMD by roughly $18,900. That reduction is permanent and compounds: every future RMD is smaller because the denominator (the IRA balance) is smaller. For married couples, reducing RMDs also reduces the Social Security taxation cliff, potentially keeping a larger share of benefits tax-free.

Roth IRAs are exempt from RMDs during the original owner's lifetime. That exemption means your heirs inherit a larger, unconstrained account — a significant estate planning benefit. See our RMD Calculator guide to model the RMD impact of different conversion amounts on your specific balance.

Roth Conversion vs Backdoor Roth: What Is the Difference?

These are often confused but they serve different purposes. A Roth conversion moves existing pre-tax IRA money into a Roth — it applies to any taxpayer at any income level. A backdoor Roth is a workaround for high earners who cannot contribute directly to a Roth IRA because they are inside or above the annual IRS income phase-out range for their filing status. The backdoor strategy involves making a nondeductible traditional IRA contribution and then immediately converting it.

The pro-rata rule complicates backdoor conversions if you have other traditional IRA balances. If you have $90,000 in a pre-tax IRA and make a nondeductible IRA contribution before converting, the IRS taxes the conversion proportionally instead of letting you isolate only the after-tax dollars. Our Backdoor Roth IRA guide explains the pro-rata rule with worked calculations, and our 2026 Roth IRA contribution limits guide keeps the annual direct-contribution limits and phase-outs separate from conversion math.

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