The Roth Conversion Calculator prices a Roth conversion before you make one: it computes the exact federal tax on converting a chosen amount from a traditional IRA, using the current bracket schedule stored in the calculator (IRS Revenue Procedure 2025-32), shows how much of the conversion fits inside your current bracket, and can project the long-run comparison against leaving the money traditional. Enter your taxable income before the conversion, the conversion amount, and filing status.
How It Works
The calculator computes tax on your income with and without the conversion; the difference is the conversion tax. Because conversions stack on top of other income, the amount is split across the brackets it passes through: the calculator reports how much lands in your current bracket, how much spills into higher brackets, the top marginal rate reached, the effective rate on the conversion, and the room that was available in your bracket before you started. Optional projection inputs (years to retirement, expected return, expected retirement tax rate, and whether the tax is paid from outside funds) extend the answer into a Roth-versus-traditional future-value comparison.
Parameters
| Input | Required | Meaning | |---|---|---| | Current taxable income | Yes | Taxable income before the conversion | | Conversion amount | Yes | Amount to move from traditional to Roth | | Filing status | No | Single or joint bracket schedule | | Years to retirement | No | Horizon for the projection | | Annual return | No | Assumed growth for the projection | | Retirement tax rate | No | Expected rate on traditional withdrawals later | | Pay taxes from outside | No | Whether conversion tax comes from funds outside the IRA |
Worked example
A single filer has 30,000, taking taxable income to 12,312; after, 6,686**. The split explains why: 105,700), and the remaining 25,700 would have kept every dollar at 22%: "filling the bracket" is the standard conversion strategy, and the bracket-room figure exists to size it precisely.
Why paying tax from outside funds matters
If the 30,000 lands in the Roth and compounds tax-free, and the outside payment effectively moves extra money from a taxable wrapper into the tax-free one. If the tax is withheld from the conversion itself, only $23,314 reaches the Roth, and for anyone under 59 and a half the withheld portion can also count as an early distribution. The projection toggle quantifies the difference over your horizon; at long horizons it is routinely the largest single variable in whether a conversion wins.
When conversion tends to win or lose
Conversions win when the rate paid now is lower than the rate that would apply later: gap years between retirement and required distributions, a temporarily low-income year, or expected higher future brackets all argue for converting. They lose when the conversion itself pushes income across expensive cliffs (Medicare IRMAA tiers, the SALT phase-out, ACA subsidy thresholds, net investment income tax), which this calculator does not model and which can add points to the true effective rate. State income tax on the conversion is also outside the federal figure shown.
Limitations
Federal brackets only, as stored for the modeled schedule; no state tax, no IRMAA, ACA, NIIT, or credit phase-outs, and no account of basis in the traditional IRA (the pro-rata rule), which can make part of a conversion tax-free and part of every distribution taxable. The projection is a deterministic illustration at your assumed return, not a forecast. Material conversions deserve a tax professional's review before execution, ideally in the same calendar year, because conversions cannot be recharacterized anymore.
The retirement context: RMDs and the widow's bracket
Conversions are usually a retirement-decade strategy because of what waits on the other side. Traditional balances eventually face required minimum distributions, which force taxable income whether you need the money or not and can push a retiree into higher brackets and Medicare tiers on the government's schedule instead of yours. Converting in the low-income years before those distributions begin trades a known, chosen rate now for an unchosen one later. A related pressure is the survivor's bracket: a couple filing jointly enjoys wide brackets, but after the first death the survivor files single on similar income, so income that was taxed at 22% jointly can land at 32% for the survivor. Money already in Roth is immune to both problems, which is why conversion analysis for couples routinely models the single-filer scenario, not just the joint one.
The five-year rules, briefly
Two separate five-year rules touch Roth money and are commonly confused. The qualification rule governs whether earnings come out tax-free in retirement (five years since your first Roth contribution plus a qualifying condition such as age 59 and a half). The conversion rule applies its own five-year clock to each conversion for penalty purposes on withdrawal of converted principal before 59 and a half. Neither changes the tax computed at conversion time, which is this calculator's subject, but both affect when converted money can be spent, so a conversion in your late fifties deserves a withdrawal timeline alongside the tax estimate.
Frequently Asked Questions
How much should I convert each year?
The common approach is to fill your current bracket: convert up to the top of the bracket you are willing to pay, which the calculator's bracket-room figure gives directly, then repeat in future low-income years.
Is the conversion tax due immediately?
It is income for the year of conversion, settled through withholding or estimated payments by the filing deadline. Underpayment penalties can apply if estimates are ignored, so plan the payment when you plan the conversion.
Can I undo a conversion?
No. Recharacterization of conversions was eliminated in 2018. The sizing decision is final, which is why modeling the bracket split before executing matters.