What the Brokerage Calculators Miss
Type a conversion amount into most online calculators and they multiply it by a bracket rate. That is the right start and the wrong finish, because for a retiree three other meters are running at the same time.
The first is Social Security. Whether your benefits are taxed depends on a formula that counts half your benefits plus essentially all your other income, and its thresholds have never been adjusted for inflation since they were set decades ago. A conversion raises that number dollar for dollar, and inside the phase-in range each converted dollar can drag another 85 cents of benefits into taxable income. Planners call it the tax torpedo. A retiree in the 22% bracket can face an honest marginal rate near 40% on converted dollars without ever leaving the 22% bracket.
The second is the new senior deduction, worth $6,000 per person 65 or older through 2028. It phases out at 6 cents per dollar of income above $75,000 for a single filer or $150,000 for a couple, so inside the phaseout band a conversion quietly gives some of it back.
The third is Medicare, which has its own section below because the bill arrives two years late, where nobody is looking for it.
There is a fourth for anyone holding a taxable brokerage account, and it is the one most often missed. Qualified dividends and long-term capital gains are taxed on their own schedule at 0, 15 or 20 percent, and they sit on top of your other income. A conversion is ordinary income, so it slides in underneath and lifts them. A retiree whose dividends were landing in the 0 percent band can convert a modest amount and watch those same dividends start costing 15 percent, on top of the tax on the conversion itself. That is why the calculator asks for dividends and long-term gains in their own box rather than lumping them in with pension income, and it reports the displacement as a separate line when it happens.
The calculator above solves all four simultaneously. When it tells you how much fills your bracket, that amount already accounts for the torpedo and the clawback, which is why it is often smaller than the plain distance to the bracket line. The difference is money you would have converted at a rate you never agreed to.
When Is the Roth Conversion Window?
For most people the cheap years run from retirement, when the paycheck stops, until required minimum distributions begin, at age 73 for anyone born in 1951 through 1959 and age 75 for anyone born in 1960 or later. In those years your bracket is briefly, artificially low, and every dollar converted at 12% or 22% is a dollar that will never come out at your RMD-swollen later rate. The full strategy, including the widow's penalty that makes converting while married so much cheaper, is on our Roth conversion window guide.
One cohort deserves a footnote nobody else gives them. If you were born in 1959, Congress managed to assign you two different RMD ages in the same statute, arguably both 73 and 75. Treasury has proposed fixing the contradiction at 73, while the final regulations pointedly left the question reserved, so 73 is the only safe planning age and it is the one this calculator uses. Anyone selling you a plan built on 75 is building on the one reading Treasury has already declined to propose.
Conversions do not stop at RMD age, but the sequence hardens. Each year's required distribution must come out first, it can never itself be converted, and converting ahead of it creates an excess contribution problem that compounds at 6% a year until fixed. If you retire early instead, years before Medicare and Social Security, the window opens wider and the Roth conversion ladder becomes the relevant playbook.
The 2026 Tax Increase That Never Happened
For years, nearly every article about Roth conversions carried the same countdown. The 2017 tax cuts were scheduled to expire after 2025, rates would snap back up in 2026, so convert now. It was true when written, and it is not true anymore. In July 2025 the rate structure was made permanent. The top rate stays at 37%, the brackets kept their widths, and the larger standard deduction survived and grew.
If a page you are reading still says convert before rates rise in 2026, it predates the law. What the repeal did not change is everything personal. Your own window between retirement and RMDs still closes on schedule. A surviving spouse will still file single, in brackets roughly half as wide, after the first death. And your children still face a 10-year clock on whatever traditional IRA you leave them. Those three reasons were always the durable case for converting, and none of them depends on what Congress does next.
The calculator prices this year. The plan is the other 20.
A conversion schedule, the beneficiary designations behind it, and the estate plan it feeds, in one conversation.
Book your free consultHow a Conversion Raises Your Medicare Premium
Medicare premiums are means-tested through a surcharge called IRMAA, and it works on a two-year delay. Your 2026 tax return sets your 2028 premium. Convert a large amount this year and the bill arrives in your 2028 premium notices, long after the conversion felt finished.
The thresholds are cliffs, not ramps. Cross one by a single dollar and the entire surcharge applies for the year, to each spouse on Medicare separately. In 2026 the first cliff sits at $109,000 of modified adjusted gross income for a single filer and $218,000 for a joint return, and there are four more above it. The calculator shows your distance to the next cliff and prices a crossing in premium dollars, which is the number that actually changes decisions. Sometimes the answer is to convert right up to $1 below a cliff. Sometimes it is to cross deliberately, because one loud premium year buys silence for the rest.
One honest limit on that arithmetic. The brackets that will govern your 2028 premium have not been published yet, so the calculator prices a crossing against the 2026 schedule. Those thresholds are adjusted for inflation every year, and they rose about 3 percent in the last one, so an income sitting just over a line today may well fall under the real 2028 line. The surcharge itself moves the other way, since premiums rose almost 10 percent in that same year. Treat a near miss as a reason to ask rather than a verdict.
Three fine points. Municipal bond interest counts toward the Medicare number even though it is tax free, which surprises people who structured around taxes. Married couples filing separately face a different, brutal schedule with no gentle first step, where one dollar over the first threshold lands directly on the second-highest surcharge. And there is no appeal. Social Security will reduce a surcharge for a short list of life-changing events, including retirement, the death of a spouse, and divorce, and its regulations say plainly that nothing outside that list counts. A Roth conversion is a choice you made, so it is not on the list.
The 2025 to 2028 Senior Deduction Wrinkle
The 2025 tax law created a $6,000 deduction per person aged 65 and up, on top of the regular standard deduction and its over-65 additions. It phases out at 6% of income above $75,000 single or $150,000 joint, and, the part that matters here, it expires after 2028.
Read the statute carefully and the phaseout is harsher for couples than it first looks. The 6% reduction applies to the $6,000 per person, and each qualifying spouse then claims the reduced figure. So a married couple who are both 65 lose 12 cents of deduction per dollar of income, not 6, and their $12,000 is entirely gone at $250,000 of income rather than surviving to $350,000. The IRS form makes the point plainly: it computes one reduced amount and then enters it twice.
Put that next to the 2028 expiry and something counterintuitive falls out for one group. A 68-year-old single filer with $100,000 of income sits inside the phaseout band, so each converted dollar costs the bracket rate plus the clawback. The same dollar converted in 2029, after the deduction and its clawback are both gone, faces the bracket rate alone. For income inside the band, the arithmetic can favor converting a little less now and more later.
Two limits on that, and they matter more than the insight does. First, it reverses below the band. If your income is under $75,000 single or $150,000 joint before the conversion, the deduction is free bracket room that simply disappears after 2028, and converting sooner usually wins. Second, the prize is bounded. The clawback cannot cost more than the deduction is worth, which caps the whole effect near $1,000 for a single filer and $2,000 for a couple across the four years. It bends close decisions; it does not overturn the ordinary case for converting early, which rests on required distributions, the widow's penalty, and your heirs, none of which expire.
Per dollar, the clawback adds about 1.4 cents for a single filer in the 24% bracket and about 2.9 cents for a couple where both are 65. The calculator prices it exactly and tells you when it is in play, and when it is not.
Money That Can Never Convert
Before any math, four gates. Money that fails them does not get a worse rate, it gets excluded, and two of the failures are expensive to attempt.
Required minimum distributions can never be converted. In an RMD year the required amount comes out first, and only dollars beyond it may convert. An inherited IRA cannot be converted by anyone except a surviving spouse who first treats the account as their own. The workaround that circulates in forums, cashing out the inherited account and moving the money into your own Roth, simply does not exist in the law, and the attempt is a fully taxable distribution. The full inheritance rulebook is on our inherited IRA RMD calculator.
A SIMPLE IRA cannot convert during the two years after the first contribution to it, on pain of a 25% penalty replacing the usual 10%. And since 2018 no conversion of any kind can be undone. The old recharacterization escape hatch is gone, so an amount converted in a panic in December is a done deal in January.
Employer plan money deserves its own caution. It can reach a Roth, but the safe lane is a direct rollover, custodian to custodian. A check made out to you personally triggers mandatory 20% withholding that you must replace from other money within 60 days, and the ways that goes wrong fill their own page, the 60-day rollover rule. One more asymmetry worth knowing. If you work past RMD age and do not own 5% of the company, that employer's plan can defer RMDs while you keep working. Your IRAs cannot.
The Estate Planning Case for Converting
We are estate planning attorneys, so here is the part of this decision that lives on our desk. A traditional IRA left to adult children lands under the 10-year rule, and for most families those are the children's peak earning years. A $900,000 IRA emptied by a 55-year-old surgeon is taxed at rates the parent never paid in their life. A Roth handed to the same child compounds tax free for the full 10 years and comes out untaxed.
Converting during your own low-bracket window is therefore a transfer of wealth disguised as a tax payment. You prepay at 22% or 24% what your children would have paid at 35% or 37%, and the tax you pay from taxable savings shrinks your estate without using a dollar of gift exclusion. It is the rare move that improves the income tax picture and the estate tax picture at the same time. What happens to the account at death, and the beneficiary paperwork that decides it, is mapped on what happens to your IRA when you die.
Two cautions from the litigation side of our practice. Every conversion opens or funds an account, and new accounts are where beneficiary designations quietly go blank, which un-does the entire plan. And naming a trust as the Roth's beneficiary can be excellent or disastrous depending on drafting done years earlier; that analysis is at naming a trust as your IRA beneficiary. For Floridians and the about-to-be, the state wedge is real too. Florida taxes none of this, so a conversion timed after a genuine move here escapes state tax entirely, starting with a declaration of domicile.
Frequently Asked Questions
How much tax will I pay on a Roth conversion?
The converted amount is added to your ordinary income for the year, so the answer depends on what bracket the new dollars land in, and on four second-order effects. A conversion can make more of your Social Security taxable, push your qualified dividends and long-term capital gains into a higher rate, claw back the temporary senior deduction if you are 65 or older, and put you over a Medicare surcharge cliff that raises premiums two years later. Stacked, those can take a household sitting in the 12% bracket past a 49% rate on the next dollar converted. The calculator above prices all of it together and shows the effective rate on your specific amount.
How much should I convert to stay in my tax bracket?
Enter your income above and the calculator shows the exact amount that fills your current bracket and the next one. The number is usually smaller than the plain distance to the bracket line, because each converted dollar can pull Social Security into taxable income or claw back the senior deduction along the way, so a dollar of conversion often adds more than a dollar of taxable income. That compounding is the main thing flat calculators get wrong. Filling a bracket exactly is a rule of thumb rather than a rule; sometimes the cheaper move is to stop short of a Medicare cliff, and sometimes it is to convert well past the bracket line because the rate on the far side is lower than the rate inside the Social Security phase-in.
Does a Roth conversion count as income for Medicare premiums?
Yes. Medicare surcharges (IRMAA) are set from your modified adjusted gross income two years earlier, and a conversion raises that number dollar for dollar. A 2026 conversion sets your 2028 premium. The thresholds are cliffs, so one dollar over a line triggers the entire surcharge for the year, for each spouse on Medicare. The calculator shows your distance to the next cliff before you pick an amount.
Can I do a Roth conversion after age 73?
Yes, with one strict rule of sequence. Once required minimum distributions have begun, each year you must take the full RMD first, and the RMD itself can never be converted. Convert before the RMD is out and the converted amount is treated as an excess Roth contribution, which carries a 6% excise tax every year until it is corrected. After the RMD is taken, converting additional dollars is allowed at any age.
What is the deadline for a 2026 Roth conversion?
December 31, 2026, and the date that matters is when the money leaves the traditional IRA, not the tax filing deadline in April. Unlike IRA contributions, a conversion cannot be made for the prior year. Custodians get busy in late December, so a conversion intended for this tax year should be requested with room to spare.
Should I pay the conversion tax from the IRA or from savings?
From savings, almost always. Paying from outside money keeps the entire converted amount growing tax free, and if you are under 59 and a half, the withheld portion is itself an early withdrawal with a 10% penalty on top of the tax. Paying the tax from a taxable account also quietly shrinks your taxable estate with no gift tax consequence, which is part of the estate planning case for converting.
Does Florida tax Roth conversions?
No. Florida has no state income tax, so a conversion here faces federal tax only. That makes timing matter for anyone moving. Convert after establishing Florida residency and the conversion escapes your old state entirely, convert before leaving a taxing state and it does not. The move has its own paperwork, starting with a declaration of domicile.
Is the sunset still a reason to convert before 2026?
That reason is gone. The individual rate structure that was scheduled to expire after 2025 was made permanent in July 2025, so the top rate stays 37% and brackets did not snap back. The durable reasons to convert are personal rather than legislative. Your own low-income years between retirement and RMDs, the survivor filing single after a first death, and heirs who must empty the account within 10 years.
Common Situations
The bracket that was not the rate. A 67-year-old widow with $58,000 of pension income and $28,000 of Social Security asked us to bless a $60,000 conversion her brokerage calculator priced at 22%. The real number was closer to 31%, because the conversion dragged most of her Social Security into taxable income on the way. She converted in three smaller annual slices instead, each sized to where the torpedo eased, and paid tens of thousands less for the same Roth.
The premium letter two years later. A couple converted $180,000 in a single December on good bracket logic, then opened their premium notices two Novembers later to find both spouses over an IRMAA cliff, about $2,300 in added premiums for the year. The conversion was still right. The size was not. Eleven thousand dollars less would have stayed under the line, and the calculator above would have said so in one glance.
The conversion that unraveled a plan. A client converted diligently for four years, and the custodian opened a fresh Roth account in year one with no beneficiary named. He died in year five. The Roth fell into his estate, through probate, and the see-through trust his old IRA pointed at never received it. The conversions were flawless and the plan still failed. Now a beneficiary audit rides along with every conversion schedule we design.
Sources of Law
- Rev. Proc. 2025-32: the 2026 rate tables (section 4.01), the standard deduction with the aged additions (section 4.14), and the maximum zero rate and 15 percent rate amounts for qualified dividends and long-term gains (section 4.03). Section 4 carries the 2026 figures; section 3 modifies the 2025 ones. irs.gov (retrieved 2026-08-19)
- IRC §151(d)(5), added by Pub. L. 119-21 §70103 (July 4, 2025), and IRS Schedule 1-A (Form 1040), Part V: the $6,000 senior deduction, its 2025 to 2028 term, the joint-filing requirement, and the two details the statute settles, namely that the 6 percent reduction applies to the per-person amount which each qualifying spouse then claims, and that this modified adjusted gross income does not include tax-exempt interest. irs.gov (retrieved 2026-08-19)
- CMS fact sheet, "2026 Medicare Parts A & B Premiums and Deductibles": the standard Part B premium of $202.90, the full IRMAA schedule including the separate married-filing-separately table, and the Part D income-related amounts. cms.gov (retrieved 2026-08-18)
- IRC §86 (taxation of Social Security benefits; the $25,000/$32,000 and $34,000/$44,000 thresholds, unindexed) and IRC §1(j) as amended in 2025 (permanent rate structure). uscode.house.gov (retrieved 2026-08-18)
- IRS Publication 590-A and the IRS rollover pages: conversion mechanics, the RMD-first rule, no recharacterization of conversions after 2017, and the 60-day and one-per-year rollover rules. irs.gov (retrieved 2026-08-17)
- 26 CFR §1.408A-4 (conversion limits; the SIMPLE IRA two-year rule at Q&A-4(b); the RMD-first rule at Q&A-6) and §1.408A-6 (the five-year clocks and ordering rules; Q&A-9 confirms conversion income counts toward Social Security taxability under §86). ecfr.gov (retrieved 2026-08-18)
- SECURE 2.0 Act §107(c), Pub. L. 117-328, Div. T (the RMD ages of 73 and 75, with the contradictory 1959 drafting); T.D. 10001, 89 FR 58886 (July 19, 2024), which reserved the question at 26 CFR §1.401(a)(9)-2(b)(2)(v); and the proposed rule REG-103529-23, 89 FR 58644, 58645 ("In the case of an employee born in 1959, the applicable age is age 73"), still proposed as of the date below. federalregister.gov (retrieved 2026-08-18)
- 42 U.S.C. §1395r(i) and SSA POMS HI 01101.020: IRMAA is computed from modified adjusted gross income for the second calendar year preceding the premium year. ssa.gov (retrieved 2026-08-18)
Updated on August 19, 2026. Reviewed by Kevin D. Klagge, Esq., Fla. Bar No. 99502. Attorney Kevin Klagge represents families, businesses, and international clients in estate and tax planning, business structuring, and international law, with a focus on Florida legal tools. He litigates estate and business issues in court. This calculator is general information based on federal law as of the date above, not legal or tax advice, and produces estimates only. It assumes the standard deduction, so it does not model itemized deductions or the medical expense deduction a conversion shrinks by raising your income, and it does not model the 3.8% net investment income tax or health insurance subsidies before age 65. State tax is not included and your facts control. We design the estate and beneficiary side of a conversion plan and coordinate the tax modeling with your CPA or advisor.