Deciding how much to convert to a Roth IRA in 2026 comes down to one number: the dollar amount that fills your current tax bracket without spilling into the next one. There is no IRS cap on the size of a conversion, so the practical limit is the tax the converted income creates. For a married couple filing jointly, one widely used target is the top of the 12% bracket, which sits at $100,800 of taxable income for 2026 (Source: IRS Rev. Proc. 2025-32).
There is no IRS limit on how much you can convert to a Roth IRA in a year. The amount to convert is set by tax, not by a rule. A common 2026 method sizes the conversion by bracket: a married-filing-jointly couple can convert up to the top of the 12% bracket, $100,800 of taxable income, minus income already expected, before the 22% rate reaches the next dollar (Source: IRS Rev. Proc. 2025-32).
How much can you convert to a Roth in a year?
There is no annual dollar cap and no income limit on Roth conversions. You can convert any amount, any number of times per year, from a traditional IRA to a Roth IRA. Income phase-outs apply only to direct Roth contributions, not to conversions (Source: IRS Publication 590-A, 2025).
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Because the converted amount is added to your ordinary income, the size of the conversion drives your tax bill, your Medicare premiums two years later, and how much of your Social Security becomes taxable. The real question is not “can I” but “how large should the number be this year.”
The income limits that stop higher earners from making direct Roth contributions ($242,000 to $252,000 of MAGI for joint filers in 2026) do not apply to conversions (Source: IRS Notice 2025-67). That is one reason higher earners often use conversions rather than direct contributions.
How the Roth conversion tax is calculated
A Roth conversion is taxed as ordinary income in the year you convert. The cost equals the amount converted multiplied by the marginal or effective rate that applies to those dollars (Source: IRS Publication 590-A, 2025). Because the converted income stacks on top of your other income, the federal tax depends on which brackets those dollars fall into rather than on a single flat rate.
The stacking is the point: the first converted dollars may be taxed at your current marginal rate, and later dollars can be taxed at a higher rate if the conversion pushes you into the next bracket. That behavior is exactly what the bracket-filling method below is built to control. For a dedicated cost breakdown with effective-rate examples, see our sibling guide on how much tax you will pay on a Roth conversion.
One structural point matters here: conversions completed in 2018 or later cannot be reversed. Recharacterization of a conversion was eliminated, so the tax you trigger is final for that year, and the conversion must be completed by December 31 to count for that tax year (Source: IRS Publication 590-A, 2025). Our note on the 2026 Roth conversion deadline covers the year-end timing.
The 2026 brackets and standard deduction that set the ceiling
The “fill the bracket” figure depends on two 2026 numbers: your target bracket ceiling and your standard deduction. The 2026 standard deduction is $32,200 for married filing jointly, $16,100 for single filers, and $24,150 for head of household (Source: IRS Rev. Proc. 2025-32). These figures reflect the One Big Beautiful Bill (P.L. 119-21) adjustments and apply to returns filed in 2027.
| 2026 rate | Married filing jointly (taxable income) | Single (taxable income) |
|---|---|---|
| 10% | $0 to $24,800 | $0 to $12,400 |
| 12% | $24,800 to $100,800 | $12,400 to $50,400 |
| 22% | $100,800 to $211,400 | $50,400 to $105,700 |
| 24% | $211,400 to $403,550 | $105,700 to $201,775 |
| 32% | $403,550 to $512,450 | $201,775 to $256,225 |
| 35% | $512,450 to $768,700 | $256,225 to $640,600 |
| 37% | $768,700+ | $640,600+ |
Source: IRS Rev. Proc. 2025-32 (tax year 2026). Taxpayers age 65 and older add $1,650 per spouse (MFJ) or $2,050 (single) to the standard deduction.
The bracket-filling worksheet: how to size the conversion
The reproducible way to answer how much to convert to a Roth IRA is to start with your projected taxable income, subtract it from your target bracket ceiling, and treat the gap as your conversion room. You then cross-check that figure against the IRMAA, NIIT, and Social Security thresholds before you convert. The steps below use 2026 figures.
- Project this year’s taxable income before any conversion. Start with expected gross income and subtract deductions, including the 2026 standard deduction of $32,200 for married filing jointly (Source: IRS Rev. Proc. 2025-32).
- Choose a target bracket ceiling. Many frameworks use the top of the 12% bracket, $100,800 of taxable income for married filing jointly in 2026, or the top of the 22% or 24% bracket for larger balances.
- Subtract step 1 from step 2. The difference is your conversion headroom inside that bracket.
- Cross-check MAGI against the next IRMAA tier, which begins above $218,000 for married couples in 2026, and the 3.8% NIIT threshold of $250,000 (Source: CMS 2026 Part B fact sheet; IRC section 1411).
- Check Social Security combined-income thresholds of $32,000 and $44,000 for married filing jointly if either spouse is collecting benefits (Source: IRS Publication 915, 2025).
- Check your state income tax, since many states tax conversion income and a few do not.
- The resulting dollar figure is the bracket-limited conversion amount for the year; repeat the exercise annually.
Here is the worksheet applied to a married couple with modest 2026 income, turning the headroom into a specific conversion target.
| Worksheet line (MFJ, 2026) | Amount |
|---|---|
| Projected taxable income before conversion | $24,000 |
| Top of the 12% bracket (target ceiling) | $100,800 |
| Conversion headroom inside the 12% bracket | $76,800 |
| Estimated federal tax on the conversion (about 12%) | about $9,216 |
Illustration using 2026 brackets (Source: IRS Rev. Proc. 2025-32). Actual tax depends on total income and deductions.
The roughly $77,000 result is the answer to “how much” for that specific household in that specific year. The same seven steps work for a single filer: someone with $80,000 of gross income minus the $16,100 standard deduction has $63,900 of taxable income, leaving about $41,800 of headroom before the top of the 22% single bracket at $105,700. The method is identical; only the inputs change.
The second-order cost cliffs the bracket math can miss
Staying inside a target income tax bracket does not guarantee the conversion is efficient. A conversion raises MAGI, which can trip separate thresholds for Medicare premiums, the 3.8% net investment income tax, Social Security taxation, and Affordable Care Act subsidies. Several of these are cliffs, where crossing by one dollar triggers a full-tier cost (Source: CMS 2026 Part B fact sheet; IRC section 1411).
| Guardrail (2026, MFJ) | Threshold | How it behaves |
|---|---|---|
| First IRMAA Medicare tier | MAGI above $218,000 | Cliff; 2-year lookback (2026 uses the 2024 return) |
| 3.8% net investment income tax | MAGI above $250,000 | Applies to investment income above the line; not indexed since 2013 |
| Social Security: up to 85% taxable | Combined income above $44,000 | Phase-in; not indexed |
| Social Security: up to 50% taxable | Combined income above $32,000 | Phase-in; not indexed |
Sources: CMS 2026 Medicare Part B fact sheet; IRC section 1411 / IRS NIIT Q&A; IRS Publication 915, 2025.
Medicare IRMAA is a two-year cliff
The Income-Related Monthly Adjustment Amount adds a surcharge to Medicare Part B and Part D premiums once MAGI exceeds a tier. For 2026 the first tier begins above $218,000 for married couples filing jointly and $109,000 for individuals, using MAGI from the 2024 return (Source: CMS 2026 Part B fact sheet). The standard 2026 Part B premium is $202.90 per month before any surcharge.
Because it is a step function, a conversion that crosses a tier by a small amount can raise premiums for the full year. The two-year lookback also means the last conversion year that does not affect a Part B premium is the year you turn 62, since premiums first apply at 65.
The 3.8% NIIT and the Social Security tax torpedo
A Roth conversion is not itself net investment income, but it raises MAGI, which can push interest, dividends, and capital gains above the 3.8% NIIT threshold of $250,000 for joint filers and $200,000 for single filers (Source: IRC section 1411). That $250,000 figure has not been indexed since it took effect in 2013, so more households cross it each year. Reviewing the 2026 net investment income tax thresholds alongside the bracket math helps keep both in view.
Separately, conversion income raises the combined-income figure that determines how much Social Security is taxed. Once combined income exceeds $32,000 (MFJ), up to 50% of benefits become taxable, and above $44,000, up to 85% do. Because those thresholds are also unindexed, a conversion can make previously untaxed benefits taxable, a pattern often called the Social Security tax torpedo.
ACA subsidies and state income tax
For households buying Affordable Care Act marketplace coverage before Medicare, added conversion income can reduce or eliminate premium tax credits, which phase out as MAGI rises (current figures are published at healthcare.gov). State income tax is another commonly missed cost, since many states tax conversion income while a handful do not.
Timing: low-income years before RMDs begin
Converting during low-income years often keeps the cost down, especially the window between leaving work and the start of required minimum distributions. Required minimum distributions begin at age 73 for those who reached 72 after December 31, 2022, and the first distribution is due by April 1 of the following year (Source: IRS Publication 590-B, 2025; SECURE 2.0 Act).
Under SECURE 2.0, the RMD age rises to 75 for individuals born in 1960 or later, and the earliest year an age-75 RMD is actually due is 2035 (Source: SECURE 2.0 Act). Converting before RMDs start reduces the future traditional IRA balance, which lowers the RMD base and the forced ordinary income it creates later. Our 2026 required minimum distribution guide covers the age rules and calculation. Note that a conversion does not satisfy an RMD. In any year an RMD is due, the required distribution must be taken first, and only additional amounts can be converted (Source: IRS Publication 590-B, 2025).
Paying the conversion tax from outside the IRA
One approach the rules allow is paying the conversion tax with taxable, non-retirement funds rather than withholding from the IRA itself. Using outside cash leaves the full converted amount inside the Roth, so more dollars grow tax-free. Withholding tax from the IRA shrinks the amount that reaches the Roth and, for those under 59.5, the withheld portion can be treated as an early distribution.
Under age 59.5, using IRA dollars to cover the tax can trigger the 10% early-withdrawal additional tax on the withheld amount (Source: IRS Publication 590-B, 2025), which is a common reason larger conversions are timed for years when outside cash is available to pay the bill.
The Roth conversion 5-year rule
Each Roth conversion starts its own separate five-year clock. Converted amounts withdrawn before five years have passed, and before age 59.5, can be subject to the 10% recapture tax on the previously untaxed portion (Source: IRS Publication 590-B, 2025). This rule is distinct from the five-year rule that governs tax-free earnings, and it applies conversion by conversion.
For a multi-year sequence of conversions, several clocks run at once, each tied to the year of its conversion, so planning access to the money accordingly can help avoid the recapture tax on the most recent amounts.
Spreading large balances and the widow’s penalty
Large traditional IRA balances are often converted across several years so that no single year pushes income into a higher bracket or across an IRMAA or NIIT threshold. Converting a whole balance at once can stack ordinary income into the 32%, 35%, or 37% rate and inflate MAGI two years before Medicare premiums are set (Source: IRS Rev. Proc. 2025-32; CMS 2026 Part B fact sheet).
A frequently overlooked sizing factor is the future survivor scenario, sometimes called the widow’s penalty. When one spouse dies, the survivor often files single, where the 2026 brackets compress and the standard deduction drops to $16,100 from the $32,200 joint amount (Source: IRS Rev. Proc. 2025-32). Income that fit a joint bracket can face a higher single rate later, which is part of why some households weigh converting more while both spouses can still file jointly.
Pro-rata rule, forms, and heirs
If you hold both pre-tax and after-tax dollars across your traditional IRAs, the pro-rata rule treats every conversion as a proportional mix of taxable and nontaxable amounts. You cannot convert only the after-tax portion; the taxable share is calculated across your combined IRA balances (Source: IRS Publication 590-A, 2025).
Conversions are reported on specific forms. The custodian issues Form 1099-R for the distribution, after-tax basis is tracked on Form 8606, and the taxable amount flows to Form 1040 for the year of the conversion (Source: IRS Publication 590-A, 2025). Keeping Form 8606 current across years documents your after-tax basis, which generally helps those already-taxed dollars avoid being taxed a second time.
On the inheritance side, Roth assets can pass to heirs without the income tax a traditional IRA carries. Under the SECURE Act, many non-spouse beneficiaries must empty an inherited account within 10 years, so leaving Roth dollars can change the tax picture for that heir (Source: SECURE Act; IRS Publication 590-B, 2025). Roth conversion planning connects this sizing question to the broader estate and tax picture.
How expected future tax rates affect the conversion decision
A conversion tends to make mathematical sense when you expect the same or a higher tax rate on those dollars later than the rate you pay to convert now. If you expect a lower rate in retirement, prepaying tax today can cost more than waiting (Source: IRS Publication 590-A, 2025). The bracket-filling method is a way to keep the rate paid today low while shifting balances out of future forced-income years.
Because conversions cannot be reversed, the rate comparison is worth doing before the number is finalized. Our page on the Roth conversion break-even point shows how the years until growth offsets the upfront tax factor into the decision (Source: IRS Publication 590-A, 2025).
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Q3 Advisors is a registered investment adviser focused on retirement tax planning. This page is educational and is not advice; consult a qualified professional.
Frequently asked questions
There is no IRS cap on how much you can convert to a Roth in a year; the practical limit is the tax the converted income creates. The questions below cover the amount, the tax, timing, and the age and five-year rules that shape the decision.
How much can you convert to a Roth in a year?
There is no IRS annual limit on Roth conversions. You can convert any amount, as many times as you want in a year, from a traditional IRA to a Roth IRA (Source: IRS Publication 590-A, 2025). The practical limit is tax: each converted dollar is ordinary income, so most 2026 plans size the amount to a target bracket rather than to a fixed cap.
Is it worth converting to a Roth?
A conversion tends to help when you expect the same or a higher tax rate on those dollars in retirement than the rate you pay to convert now (Source: IRS Publication 590-A, 2025). It can also reduce future required minimum distributions and leave tax-free assets to heirs. Because conversions are irreversible and taxable in the year made, the rate comparison matters before deciding.
How much tax will I pay if I convert to a Roth IRA?
The tax equals the converted amount times your marginal or effective rate for that year, because the conversion is taxed as ordinary income (Source: IRS Publication 590-A, 2025). Since the converted income stacks on your other income, a conversion that stays inside the 12% bracket carries a lower effective cost than one that reaches the 22% or higher brackets. State income tax may apply on top, depending on where you live.
At what age does it not make sense to convert to a Roth?
There is no age cutoff in the rules, but the calculus can shift once required minimum distributions begin at age 73 for those who reached 72 after December 31, 2022 (Source: IRS Publication 590-B, 2025). RMDs must be taken before converting and cannot be satisfied by a conversion, which reduces the low-income headroom the bracket-filling method relies on.
How do I avoid paying taxes on a Roth conversion?
Conversions are generally taxable, so the realistic goal is minimizing tax rather than avoiding it. Common approaches the rules allow include converting only up to your standard deduction and low brackets, converting in low-income years, and spreading large balances across multiple years (Source: IRS Rev. Proc. 2025-32). A conversion sized to the 2026 standard deduction alone can face little or no federal income tax.
Should I convert my entire IRA to a Roth at once?
Converting an entire balance in one year can stack ordinary income into the 32%, 35%, or 37% bracket and inflate the MAGI that sets Medicare premiums two years later (Source: IRS Rev. Proc. 2025-32; CMS 2026 Part B fact sheet). Spreading conversions across several years is a common way to keep each year inside a target bracket and under IRMAA and NIIT thresholds.
What is the 5-year rule for Roth conversions?
Each conversion starts its own separate five-year clock. Converted amounts withdrawn before five years pass, and before age 59.5, can face a 10% recapture tax on the previously untaxed portion (Source: IRS Publication 590-B, 2025). In a multi-year conversion sequence, several clocks run at once, each tied to the year of its conversion.
How much can I convert to a Roth without paying taxes?
Roughly the amount that fits under your deductions and lowest brackets. For 2026, a married couple filing jointly with no other taxable income could convert up to the $32,200 standard deduction with little or no federal income tax, and beyond that at 10% and 12% inside the bracket (Source: IRS Rev. Proc. 2025-32). State tax may still apply.
Sources
IRS, “IRS releases tax inflation adjustments for tax year 2026” and Rev. Proc. 2025-32 (2026 brackets and standard deduction): https://www.irs.gov/newsroom/irs-releases-tax-inflation-adjustments-for-tax-year-2026-including-amendments-from-the-one-big-beautiful-bill
IRS Publication 590-A (2025), contributions to and conversions of IRAs: https://www.irs.gov/publications/p590a
IRS Publication 590-B (2025), distributions, the conversion five-year rule, and RMDs: https://www.irs.gov/publications/p590b
IRS, Required Minimum Distributions FAQs (SECURE 2.0 age 73): https://www.irs.gov/retirement-plans/retirement-plan-and-ira-required-minimum-distributions-faqs
CMS, “2026 Medicare Parts A & B Premiums and Deductibles” (IRMAA thresholds): https://www.cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles
IRS, “Questions and Answers on the Net Investment Income Tax” and IRC section 1411: https://www.irs.gov/newsroom/questions-and-answers-on-the-net-investment-income-tax
IRS Publication 915 (2025) and Notice 703, Social Security benefit taxation: https://www.irs.gov/publications/p915
IRS Notice 2025-67, 2026 retirement plan and IRA limits: https://www.irs.gov/newsroom/401k-limit-increases-to-24500-for-2026-ira-limit-increases-to-7500
