Roth Conversion Calculator
Estimate the true, all-in cost of converting traditional IRA or 401(k) funds to a Roth. A conversion raises your income in ways that can cost more than the bracket rate alone: it can pull Social Security into the taxable range (the "tax torpedo"), trigger the 3.8% Net Investment Income Tax, push you across a Medicare IRMAA income threshold (raising your Part B and D premiums two years later), and reduce your ACA Marketplace premium tax credits (subsidies). If you pay the tax from the IRA before age 59.5, a 10% early-withdrawal penalty applies too. See your bracket headroom, the all-in cost at each conversion size, and how much actually lands in your Roth.
What This Calculator Does
This calculator estimates the federal and state income tax cost of converting a traditional IRA or 401(k) to a Roth account. Enter your filing status, income sources, and state to see exactly how much room you have in each tax bracket and what a conversion would cost at each level.
A bracket chart at the top of the results plots your actual marginal rate across the income range. Colored bands behind the curve show the federal bracket schedule; the curve itself lifts above the underlying band wherever your real marginal rate exceeds the bracket rate - most often where the enhanced senior deduction phases out, or where a conversion pulls additional Social Security into the taxable pool (the "tax torpedo"). A white marker shows where your current income sits, a magenta marker shows where a custom conversion amount would land, and - if anyone in the household is on Medicare - amber dashed lines flag each IRMAA threshold in range, so a large conversion shows every tier it would cross, not just the first. The colored bands already mark each bracket transition, so bracket-fill targets are read off the band edges rather than as separate lines.
Below the chart, the conversion options are shown bracket by bracket in a single comparison table - fill to the top of the 12%, 22%, or 24% bracket (and 32% / 35% when you show higher brackets), with IRMAA thresholds flagged if you or your spouse are on Medicare. If anyone in the household is on Medicare, an optional IRMAA-aware toggle caps each suggestion at the highest IRMAA tier still inside that bracket - so each option lands on a different deliberate tier instead of overshooting an IRMAA boundary. If you have ACA Marketplace coverage, enable the optional ACA tab to see how a conversion could affect your premium tax credit and what your all-in cost would be after both taxes and subsidy changes.
Use the Custom column in the table to evaluate any specific target alongside the bracket-fill options and see the combined cost. If you want to see how a conversion fits into your broader retirement income picture, the Social Security calculator can help you model overall cash flow alongside your Roth strategy. If you have a pension and are weighing annuity versus lump sum options, the pension & lump sum calculator can help you see how that guaranteed income affects your available bracket space for conversions.
When This Matters
- You're in a low-income year - retired but not yet drawing Social Security or RMDs
- You have a gap between retirement and age 73 when required minimum distributions begin
- You expect tax rates - yours or the statutory brackets - to be higher in the future
- Your traditional IRA is large enough that future RMDs will push you into a higher bracket
- You have ACA Marketplace coverage and want to understand how a conversion would affect your premium tax credit
- You want to reduce the taxable portion of your estate for heirs
How to Use This Calculator
- Select your filing status, state, and tax year on the Tax Situation tab
- Enter your income sources on the Income tab to set your starting taxable income
- If you have Marketplace health coverage, enable ACA modeling on the ACA / Marketplace tab and enter your benchmark premium
- Scan the bracket chart to see where your current income sits in the marginal-rate curve - lifts above the bracket band show where your real marginal rate exceeds the bracket rate - the enhanced senior deduction phasing out, or Social Security entering the taxable pool (the "tax torpedo") - and amber dashed lines flag each IRMAA threshold in range if anyone in the household is on Medicare
- Review the Conversion Options table to compare the tax cost at each bracket boundary side by side
- Check the IRMAA warning if you or your spouse are on Medicare. Optionally toggle IRMAA-aware in the Conversion Options header to cap each option at the highest IRMAA tier inside its bracket.
- Type a dollar amount into the Custom column if you have a specific target in mind - it sits alongside the bracket-fill options for easy comparison
Frequently Asked Questions
How much of my IRA should I convert?
There's no single answer - it depends on your current bracket, projected future RMDs, and other income. A common approach is to fill your current bracket each year without crossing into the next one. This calculator shows exactly how much room you have at each threshold.
Does a Roth conversion affect Medicare premiums?
Yes - if your modified adjusted gross income (MAGI) exceeds certain thresholds, you'll pay higher Medicare Part B and Part D premiums two years later (called IRMAA surcharges). Medicare looks back two years to determine the current year's surcharge, so a conversion in 2026 would affect 2028 premiums. The calculator flags this when your conversion would trigger IRMAA and shows the relevant thresholds so you can stay below them if desired. When a conversion does cross a threshold, the calculator adds the resulting annual surcharge - for everyone in the household on Medicare - into the conversion's total tax cost, so the headline figure reflects the IRMAA hit rather than just warning about it. For households on Medicare, the optional IRMAA-aware toggle (in the Conversion Options header) reshapes each bracket-fill option to land at a specific IRMAA tier inside that bracket rather than overshooting it, so you can see deliberate tier choices side-by-side.
How does a Roth conversion affect ACA Marketplace subsidies?
A Roth conversion increases your modified adjusted gross income (MAGI), which is the income measure used to determine ACA premium tax credits. A larger conversion can reduce or eliminate your subsidy, raising your net health insurance cost. Enable the ACA / Marketplace tab to see the subsidy impact alongside the tax cost for each conversion option.
What is the benchmark premium?
The benchmark premium is the cost of the second-lowest-cost Silver plan (SLCSP) available in your area. The ACA uses this amount to calculate your premium tax credit - it is not necessarily the plan you are enrolled in. You can find your benchmark premium at healthcare.gov/tax-tool or on Form 1095-A if you already have Marketplace coverage.
What is the "all-in rate" on a conversion option?
When a Roth conversion would reduce an estimated ACA premium tax credit, the calculator switches the headline rate to "all-in" and combines the tax cost (federal and state income tax, plus any NIIT and IRMAA the conversion triggers) with the subsidy you would lose. This gives you a more complete picture of the true cost of converting. The tax-only rate is shown alongside so you can see both. When a conversion stays within the same subsidy tier, the row stays labeled "Effective rate".
Why does the marginal-rate curve spike above the bracket rate?
The most common cause is the enhanced senior deduction from the One Big Beautiful Bill Act - if anyone in your household is age 65 or older and you're taking the standard deduction, you're eligible for $6,000 per qualifying senior (available 2025-2028). That deduction phases out at 6 cents per dollar of MAGI above $150,000 (MFJ) / $75,000 (single), and is fully gone at MAGI ~$250,000 / ~$175,000. Inside that phase-out window every extra $1 of MAGI removes 6¢ of deduction per senior - which then gets taxed at your marginal bracket rate. With two seniors the effect is 12¢ per $1, so a dollar that would face 24% actually costs 24% × 1.12 = 26.88% until the deduction is fully phased out. The chart shows this real combined rate, so the spike appears wherever your MAGI sits inside the phase-out window - which falls in the upper-22%/24% range and shifts with your filing status and other income, not at one fixed bracket boundary - and drops back to the plain bracket rate once MAGI clears the top of the window. A conversion landing inside the window costs noticeably more per dollar than the bracket rate alone suggests; landing just past it avoids the lift entirely. The curve can also spike for other reasons it models: Social Security becoming taxable as income rises (the "tax torpedo") can lift the effective rate at much lower income, and crossing an IRMAA tier adds a jump if you or your spouse are on Medicare.
What does "Your current income" mean above the chart?
It's your gross ordinary income - wages, self-employment, the taxable portion of Social Security, pensions, RMDs, IRA/401(k) withdrawals, and other ordinary income - before the standard or itemized deduction is subtracted. It does not include long-term capital gains or qualified dividends; those have their own bracket schedule and are stacked on top of ordinary income for tax purposes. This is the figure that determines where you sit on the bracket chart's X-axis. It's close to your AGI for households without significant capital gains, but it isn't MAGI - MAGI also includes capital gains, tax-exempt interest, and certain add-backs, and is what IRMAA and ACA subsidy calculations actually look at.
What's the best window for Roth conversions?
Most people find the best window is after retiring but before Social Security and RMDs begin - typically ages 60-72. Taxable income is often at its lowest during this period, making conversions relatively cheap. The earlier in that window, the more years the converted funds have to grow tax-free.
Do I owe state taxes on a Roth conversion?
Most states tax Roth conversions as ordinary income. A few states (Florida, Texas, Nevada, and others) have no income tax, and some partially exempt retirement income. Select your state in the calculator to include state taxes in the estimate.
What's the difference between a Roth conversion and a Roth contribution?
A Roth contribution is money you put directly into a Roth IRA and is subject to income limits. A Roth conversion moves existing pre-tax money from a traditional account into a Roth - there are no income limits for conversions, but you pay income tax on the amount converted in the year it happens.
Can I undo a Roth conversion?
No - recharacterization (reversing a conversion) was eliminated by the Tax Cuts and Jobs Act of 2017. Once converted, the tax is owed for that year. This makes planning the conversion amount carefully more important, since there's no way to walk it back.