US Roth Conversion Tax Calculator

The converted amount is added to your ordinary income for the year and taxed at your marginal rates — there is no separate Roth conversion rate and no preferential capital gains treatment. On a $80,000 income with a $50,000 conversion and no after-tax basis, a single filer in 2026 pays roughly $11,160 of federal tax on the conversion, an effective rate of about 22.3%, because most of it falls in the 22% bracket and the top slice reaches 24%. State tax is on top of that.

The IRS treats every traditional, SEP and SIMPLE IRA you own as a single pot when working out how much of a conversion is taxable. You cannot choose to convert only your after-tax money. If you have $500,000 across your IRAs of which $50,000 is non-deductible basis tracked on Form 8606, then 90% of any conversion is taxable and 10% comes out tax-free, no matter which account the money physically leaves. Workplace 401(k) balances are excluded from the calculation, which is why rolling an IRA into a 401(k) is a common way to clear the pot.

No. Recharacterisation of Roth conversions was removed by the Tax Cuts and Jobs Act of 2017, so a conversion is irrevocable once made. Before that change you could reverse a conversion up to the extended filing deadline if markets fell, which made conversions close to risk-free. They are not any more. Because you cannot walk it back, the amount should be sized before you convert rather than adjusted afterwards, and converting in tranches through the year rather than in one December transaction gives you more control.

No. There is an income limit on direct Roth IRA contributions, but none on conversions, and none on the amount you can convert. That asymmetry is the whole basis of the backdoor Roth strategy, where a high earner makes a non-deductible traditional IRA contribution and converts it. The catch is the pro-rata rule: if you hold other pre-tax IRA money, most of that conversion will be taxable even though the contribution itself was after-tax.

Yes, through IRMAA, the income-related monthly adjustment amount added to Medicare Part B and Part D premiums. IRMAA works on a two-year lookback, so a conversion made in 2026 is measured against your 2028 premiums. For 2026, the first surcharge tier begins at $109,000 of modified AGI for single filers and $218,000 for joint filers. It is a cliff, not a taper — one dollar over the threshold triggers the full surcharge for both spouses on a joint return, which is why conversions are usually sized to stop just short of a tier boundary.

Not on the conversion itself — distributions from retirement accounts are excluded from net investment income. But the conversion increases your modified AGI, and NIIT is charged on the lesser of your net investment income and the excess of modified AGI over $200,000 single, $250,000 joint or $125,000 married filing separately. So a conversion can pull dividends, interest and capital gains you already had into the 3.8% charge. This calculator shows that indirect cost separately, because it is the one people miss.

There are two five-year clocks and they do different things. The contribution clock starts with your first ever Roth contribution and governs whether earnings come out tax-free. The conversion clock starts on 1 January of each conversion year and governs whether the converted principal can be withdrawn without the 10% early distribution penalty if you are under 59½. Each conversion has its own clock. If you are over 59½ and have had any Roth IRA open for five years, neither is a practical constraint.

From outside money, wherever possible. Withholding the tax from the conversion itself means less lands in the Roth, and if you are under 59½ the withheld amount is treated as a distribution rather than a conversion and can attract the 10% early distribution penalty on top. Paying from a taxable account also has the incidental benefit of moving money from a taxed environment into a tax-free one. If the only way to fund the tax is from the IRA itself, the case for converting at all is usually weaker.

In a year when your marginal rate is unusually low relative to the rate you expect in retirement. The classic windows are the gap years between stopping work and starting Social Security or required minimum distributions, when income can be very low; a year with a business loss or large deductions; and a year when markets have fallen, so the same shares convert at a lower value. For anyone approaching 65, the two or three years before Medicare enrolment are valuable because IRMAA's two-year lookback has not yet started biting.

Usually enough to fill your current bracket and no more. Converting to the top of the 22% or 24% bracket and stopping is the standard approach, because the next dollar jumps to a materially higher rate. This calculator shows the remaining headroom in your bracket after the conversion you have entered, so you can size it to the boundary. Where IRMAA applies, the IRMAA threshold is often the binding constraint rather than the bracket, since it is a cliff.

No, and the ordering matters. If you are of RMD age, the required minimum distribution for the year must be taken first and cannot itself be converted. Only amounts above the RMD can go into the Roth. Converting before satisfying the RMD creates an excess contribution in the Roth IRA that has to be corrected. This is one of the most common mechanical errors in conversions done late in the year.

It can. The proportion of Social Security benefits that is taxable depends on combined income, so a large conversion can increase the taxable share of benefits at the same time as being taxed itself. That interaction produces marginal rates well above the headline bracket rate — the effect sometimes described as the tax torpedo. If you are drawing Social Security, include the taxable portion in the other income field and check the marginal rate this calculator reports rather than assuming the bracket rate applies.

You can convert securities in kind, and there are good reasons to. Transferring shares directly avoids being out of the market between selling and rebuying, and the taxable amount is the fair market value on the date of conversion. Converting depressed holdings in kind after a market fall is a well-established tactic: the same shares generate a smaller tax bill, and any subsequent recovery happens inside the Roth where it is never taxed again.

Usually not on the pure arithmetic, if that assumption holds. Conversions win when you pay tax at a lower rate now than you would later. But the comparison is rarely that simple: required minimum distributions can force income up, the death of a spouse moves the survivor to single brackets at roughly half the thresholds, and inherited IRAs must generally be emptied within ten years, often during the beneficiary's highest-earning decade. Those effects push the effective future rate up and are the main reason conversions still make sense for people who expect lower income in retirement.

This is where it gets difficult, and it is the single most consequential question for Americans in Britain. HMRC does not necessarily mirror the US treatment of a Roth. The conversion is a taxable event in the US, and depending on your UK residence position and how the US/UK treaty applies to the arrangement, the UK may or may not recognise the resulting Roth as a tax-free wrapper — meaning you can pay US tax on the conversion now and still face UK tax on the eventual growth or distributions. Do not convert while UK resident without advice on both sides. Our guide to [Roth IRA conversions for Americans in the UK](/resources/blog/roth-ira-conversion-americans-uk) covers the treaty analysis.

Generally no, and this is the trap. A Roth conversion is US-source income, so foreign tax credits from UK earnings usually cannot shelter it — foreign tax credits can only offset US tax on foreign-source income within the same category. Many Americans in the UK have large excess foreign tax credit carryforwards and assume those will absorb a conversion. They will not. See our comparison of [the foreign tax credit and the FEIE](/resources/blog/foreign-tax-credit-vs-feie) for how the sourcing and category rules work.

No. It computes federal income tax and the Net Investment Income Tax only. Most states tax conversions as ordinary income, and a few do not tax retirement income at all, so the state position can swing the answer materially — and it is a genuine reason some people wait until they have moved before converting. If you are living abroad, check whether your former state still considers you resident, since several states are aggressive about this. Our guide to [state tax for Americans abroad](/resources/blog/state-tax-americans-abroad) explains where the risk sits.

Because we restate only figures we have verified against a primary IRS source, and the 2026 head of household bracket thresholds are not among them. Single, married filing jointly and married filing separately are all taken from the IRS 2026 inflation adjustment release. If you file as head of household, the single option will over-state your tax somewhat, since head of household brackets are wider — treat the result as an upper bound and ask us for an exact figure.

The calculation runs entirely in your browser and nothing is stored unless you choose to download the branded PDF report, at which point you provide your name and email so we can send it. Phone and address are optional.

If the conversion is large, if you are within two years of Medicare enrolment, if you hold after-tax basis across several IRAs, or if you have any UK or other foreign tax exposure, then yes — and before the conversion, because it cannot be reversed. Book a free 20-minute call with a TaxStone Enrolled Agent and ACCA accountant and we will model the US and UK positions together.