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Roth Conversion Window Calculator

Model a full or partial Roth conversion with the 2026 federal tax brackets, entered taxable income, state tax, future tax assumptions, and the opportunity cost of paying tax from outside cash.

Quick answer: Estimate incremental 2026 federal bracket tax, state tax, bracket headroom, and comparable future value for a Roth conversion scenario. Enter Traditional IRA balance, Amount to convert this year, Current taxable income, and Filing status to personalize the estimate. It returns Recommendation, Tax due on conversion, and Future Roth value so you can compare the impact before choosing a next step. Use it to compare long-term value, tax impact, risk, time horizon, and contribution choices.

Your situation
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Current option
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Alternatives
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Assumptions
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Your decision

Convert partially. Converting $50,000 costs about $12,420 in modeled tax now and would be worth $119,828 tax-free in 15 years — versus $85,078 after tax if left in the traditional IRA.

Recommended: Convert partially

Recommendation

Good

Convert partially

Driven by the gap between your current and retirement tax brackets, and whether you can pay the tax from cash.

Tax due on conversion

Watch

$12,420

at 24.84% combined

Federal + state on the converted amount, owed this year.

Future Roth value

Good

$119,828

tax-free

Grows and is withdrawn tax-free in retirement.

Net advantage vs traditional

Good

$4,985

Future Roth value minus the after-tax value of leaving it in the traditional IRA.

Ranked options

  1. #1Convert partially

    Fill the top of your current bracket without spilling into the next one or crossing an IRMAA threshold.

    Confidence: MediumEffort: LowRisk: Low

  2. #2Convert now (full amount)

    Locks in the modeled effective 24.84% conversion tax rate; best when the comparable future tax rate is higher.

    Confidence: MediumEffort: LowRisk: Medium

  3. #3Wait

    Better if your bracket will be lower in retirement, or if you cannot pay the tax from outside cash.

    Confidence: MediumEffort: LowRisk: Low

Watch-outs

  • • The entered conversion exceeds the approximately $10,800 remaining in your current 2026 federal bracket. A partial conversion may avoid taxing part of it at a higher marginal rate.
  • • Federal conversion tax uses the 2026 single or married-filing-jointly brackets. The model excludes basis, deductions, credits, NIIT, ACA credits, IRMAA, future state changes, and RMD effects. Confirm with a tax professional before converting.

Assumptions used

Conversion amount
$50,000
Current federal bracket
12.00%
Current bracket headroom
$10,800
Retirement bracket
24.00%
Years to retirement
15
Expected return
6.00%
Pay tax from
Outside cash

Estimates based on your assumptions above — roughly indicative, not financial, tax, or legal advice.

Next steps

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Why this matters

A Roth conversion is a tax-timing decision. The model calculates incremental federal tax across the 2026 brackets and identifies when an entered conversion spills into the next bracket. It does not calculate IRMAA, ACA credits, IRA basis, or an actual tax return.

Frequently asked questions

When does a Roth conversion make sense?
A conversion may make sense when the effective tax rate on the conversion is below the tax rate expected on future withdrawals. This estimate uses 2026 federal brackets and your entered state and retirement-rate assumptions; it is not a tax-return calculation.
Why does the calculator include outside-cash opportunity cost?
Paying conversion tax from cash lets the full amount enter the Roth, but that cash could otherwise remain invested. The comparison grows that tax payment at the same entered return so paying from cash is not treated as a free advantage.
What is the risk of converting too much at once?
A large conversion can push taxable income into a higher federal bracket and may affect Medicare IRMAA or ACA premium credits. This tool identifies federal bracket spillover only; use the linked IRMAA tool and professional tax software for other thresholds.
How is this different from the IRMAA calculator?
This tool answers whether and roughly how much to convert based on your tax-bracket bet. Our Roth Conversion with IRMAA Cliff calculator sizes the exact amount you can convert before crossing the next Medicare threshold. Use them together.

This tool produces estimates based on the assumptions you enter. It is not financial, tax, or legal advice. Actual rates, fees, and outcomes depend on your lender, account terms, and approval.