Roth Conversion Calculator
Your income, the conversion and your bracket
Your result will appear here
Fill in the fields on the left and this updates as you type.
Know what this estimate is based on
- Jurisdiction
- General mathematical model
- Scope and limitations
- Scenario model, not a forecast. Returns, volatility, inflation, fees, and taxes are assumptions and actual investment outcomes can be lower or negative.
- Source links checked
- Jul 30, 2026
Built and regression-tested by Smart Tools Lab. It has not been individually reviewed by a licensed financial, tax, or legal professional.
How to use
- 01
Enter your taxable income before any conversion and the amount you are thinking of converting.
- 02
Check the bracket fields. They open at the 2026 single figures — the 22% bracket runs to $105,700, and the next rate is 24%. Replace them for a different status or bracket.
- 03
Add your state rate, the years to retirement and the return you expect.
- 04
Read the room left in your bracket, then the tax on the amount you actually entered — split into the part taxed at your current rate and the part spilling into the next.
Formula
Headroom = bracket top − income before converting. Federal tax = min(conversion, headroom) × current rate + the remainder × next rate. Add state tax on the whole conversion. Future value = conversion × (1 + return)^years, tax-free.
Example
On $90,000 of income with the 22% bracket topping out at $105,700, you have $15,700 of headroom. Converting $40,000 costs $3,454 on the first $15,700 and $5,832 on the $24,300 above it, plus $2,000 of state tax at 5% — $11,286 in all. It also takes MAGI to $130,000, past the $109,000 IRMAA threshold, so Medicare premiums rise two years later.
Definitions
- Bracket top
- The income at which your current rate ends and the next one begins. $105,700 for a single filer in the 22% bracket in 2026.
- IRMAA
- The income-related surcharge on Medicare Part B and Part D, set from the tax return you filed two years earlier.
- Pro-rata rule
- If you hold pre-tax IRA money anywhere, a conversion is taxed in proportion across all of it — you cannot convert only the after-tax part.
Good to know
Choosing the year you pay
A conversion moves money from a pre-tax retirement account into a Roth, and the whole converted amount is added to this year's taxable income. That sounds like a cost, and it is — but it is a cost you choose the timing of. The point of a conversion is to pay tax in a year when your rate is low rather than in a year when it is high: an early-retirement gap between leaving work and starting Social Security, a year with a business loss, a sabbatical. Money converted in a 12% year and withdrawn tax-free later beats the same money left to be taxed at 22% or 24% in a year when required distributions and Social Security are both running.
Filling a bracket rather than crossing one
This is why the headline here is headroom rather than tax. Brackets are marginal, so converting up to the top of the one you are already in costs only the rate you are already paying, while a dollar past it costs the next rate up. On $90,000 of income with the 22% bracket topping out at $105,700, the first $15,700 converted costs 22 cents on the dollar and everything after it costs 24. Converting exactly to the top of a bracket, year after year through a low-income window, is the standard technique — a conversion ladder — and it is far cheaper than one large conversion that runs through two or three brackets at once.
The thresholds that are not brackets
Income does more than set a bracket, and a conversion can trip several thresholds at once. Medicare's IRMAA surcharge is the sharpest: it is set from the return you filed two years earlier, so a conversion at 63 raises premiums at 65, and it is a cliff rather than a slope — one dollar over $109,000 single or $218,000 joint in 2026 triggers the entire tier. A conversion can also raise the taxable share of Social Security benefits, push investment income past the 3.8% net investment income tax threshold, and reduce a Marketplace premium tax credit for anyone under 65. None of these appear in the bracket table, and all of them are why the conversion amount deserves arithmetic rather than a round number.
Where the tax money comes from
The single most common way a conversion backfires is paying the tax out of the conversion itself. Doing so shrinks the balance that was supposed to compound tax-free by the exact amount of the tax — and under 59½, the withheld portion is treated as an early distribution, so the 10% penalty lands on it too. Paying from taxable savings keeps the whole converted amount working. Two other rules are worth knowing before converting: each conversion carries its own five-year clock before the converted principal can be withdrawn penalty-free, and a conversion can no longer be undone — recharacterization of a conversion was repealed in 2017, so the decision is final in the year you make it.
Frequently asked questions
What is bracket-fill headroom?
The dollars you can still convert before your income crosses into the next bracket. Converting exactly that much is the cheapest possible conversion: every dollar is taxed at the rate you are already paying, and none at the higher one above it.
Should I pay the conversion tax out of the money I convert?
No, and this is the single most common way the move backfires. Paying from outside the account keeps the whole converted balance compounding tax-free. Paying from the conversion shrinks the balance by the tax — and under 59½ that withheld amount is itself an early distribution, so it can carry the 10% penalty as well.
Why does this page care about Medicare?
Because a conversion raises your MAGI, and Medicare sets Part B and Part D surcharges from the return you filed two years earlier. A conversion at 63 can raise premiums at 65. IRMAA is also a cliff, not a slope: a dollar over a threshold triggers the whole tier.
When is a conversion usually worth it?
In a year your income dips — early retirement before Social Security and RMDs start, a gap year, a business loss — because the conversion is taxed at a rate lower than the one you would face later. It also removes future RMDs on the converted money and leaves heirs a tax-free account.
Can I undo a conversion I regret?
No. Recharacterizing a Roth conversion was repealed by the 2017 tax act. Once converted, it is converted, which is why it is worth sizing the tax before rather than after.