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: Compare an entered gross IRA distribution, a calculated partial distribution and leaving that money unconverted under stated tax and return assumptions. Enter Traditional IRA balance, Gross IRA amount distributed for conversion, Current federal taxable income, and Filing status to personalize the estimate. It returns Scenario comparison, Tax due on gross IRA distribution, 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 decision
Entered gross distribution scenario has the largest modeled net future value. A $50,000 gross IRA distribution costs $12,420 in modeled tax and produces a future Roth value of $119,828, assuming qualified withdrawals, versus $85,078 for the same amount left in the traditional IRA. Net comparison includes the future opportunity cost of outside cash used for tax.
Scenario comparison
Entered gross distribution scenario
Ordered by recomputed net future value, including losses. This does not optimize a conversion or assess excluded tax and coverage rules.
Tax due on gross IRA distribution
Watch$12,420
at 24.84% combined
Federal plus state tax on the fully taxable gross IRA distribution.
Future Roth value
Good$119,828
assuming qualified withdrawals
Assumes qualified Roth distributions; eligibility and five-year rules are not determined.
Net future advantage vs traditional
Good$4,985
Future Roth value minus traditional after-tax value and future opportunity cost of outside cash spent on conversion tax. This is not an annual saving.
Ranked options
- $4,985future difference
#1Entered gross distribution scenario
Locks in the modeled effective 24.84% conversion tax rate; best when the comparable future tax rate is higher.
Confidence: MediumEffort: LowRisk: Medium - $3,106future difference
#2Current-bracket scenario ($10,800 gross)
Recomputed at the smaller of the entered amount and remaining current-bracket room. This does not check IRMAA, ACA or credit thresholds and is not an optimized conversion.
Confidence: MediumEffort: LowRisk: Medium - $0future difference
#3Leave the entered amount in traditional
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.
- • Assumes an entirely pretax IRA and qualified future Roth withdrawals; age and five-year eligibility are not determined. Federal tax uses 2026 single or joint brackets on income already reduced by deductions. The state rate stays flat and unchanged in retirement.
- • Outside tax cash is assumed to earn the same return without tax drag. Partial cash/IRA tax funding, IRA basis, credits, Social Security taxation, NIIT, ACA, IRMAA and RMD effects are excluded. Confirm these assumptions with a tax professional.
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%
- Tax funding assumption
- Entire tax from outside cash
Estimates use the amounts and assumptions you enter. Confirm the rules and your circumstances before acting.
Next steps
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<script>(function(){window.addEventListener("message",function(e){if(e.origin!=="https://www.switchwize.com")return;var d=e.data;if(!d||d.type!=="sw-embed-resize")return;var f=document.getElementsByTagName("iframe");for(var i=0;i<f.length;i++){if(f[i].contentWindow===e.source){f[i].style.height=d.height+"px";break;}}});})();</script>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?
Why does the calculator include outside-cash opportunity cost?
What is the risk of converting too much at once?
How is this different from the IRMAA calculator?
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.