Roth Conversion Planner
See the real cost of a Roth conversion — stacked through the 2026 tax brackets — the break-even future tax rate, and exactly how converting vs. waiting compares over time.
Paying with outside money keeps the full amount working in the Roth; the account type sets how heavily its growth would have been taxed.
How this works
A conversion is added on top of your existing taxable income, so it can span several brackets. The planner runs your income through the 2026 federal brackets before and after the conversion; the difference is the real federal tax, shown as an effective rate on the amount converted.
The heart of the tool is the break-even tax rate (BETR), the future rate at which converting and waiting come out even. It often lands below your current rate, which is why a conversion can pay off even when you expect lower rates later. The worked example further down this page walks through exactly this idea, with real numbers and the full comparison.
The formula & assumptions
Data & sources
2026 federal brackets: IRS Revenue Procedure 2025-32 (post-OBBBA). Break-even methodology & worked example: Vanguard, “BETR: a better way to gauge Roth conversions.”What each input means
A quick guide to the numbers the planner asks for and how each one moves the result.
Taxable income before conversion
Your ordinary income after deductions. The conversion stacks on top of it, so this sets which brackets the converted dollars fall into.
Amount to convert
How much you move from a pre-tax IRA or 401(k) into a Roth this year.
Years to withdrawal
How long the money grows before you tap it. Longer horizons make converting more attractive.
Growth rate
The annual return you expect. Faster growth increases the value of tax-free Roth space.
Expected tax rate in retirement
What you would pay on withdrawals if you did not convert. The break-even rate is measured against this number.
Pay the conversion tax from
Outside money keeps the full amount compounding in the Roth; paying from the IRA itself removes much of the benefit. For outside money, the account type sets the assumed tax drag on its growth: about 20% for tax-efficient investments, 48% for tax-inefficient investments, and 85% for cash, calibrated to the scenarios in Vanguard’s research. Higher drag means a lower break-even rate.
State tax
A flat state rate applied to both the conversion today and your withdrawals later.
Considerations
A conversion touches more than one tax form. These are the ripple effects worth weighing, ideally with a tax professional, before you pull the trigger.
IRMAA (Medicare premiums)
A conversion raises your MAGI, and Medicare uses MAGI from two years earlier to set Part B and Part D premiums. A large conversion can bump you into a higher IRMAA tier for a year.
ACA marketplace subsidies
If you are under 65 and buy coverage on the ACA marketplace, premium tax credits are based on MAGI. A conversion can shrink or even eliminate your subsidy for that year.
Social Security taxation
Adding income can increase how much of your Social Security benefit is taxable, up to 85%. Converting before you claim (or in lower-income years) can soften this.
Where you pay the tax
Paying from cash keeps the entire converted amount growing tax-free in the Roth. Paying from the IRA itself withdraws money that could have compounded, and erases much of the benefit.
No undo button
The IRS ended recharacterization in 2018. Once converted, a conversion cannot be reversed, which is a strong argument for measured annual slices over one big move.
The five-year clock
Each conversion starts its own five-year period before that money can be touched penalty-free if you are under 59½. Converting earlier starts the clocks earlier.
Future RMDs
Required Minimum Distributions begin at 73 (age 75 if you were born in 1960 or later). Converting now shrinks your pre-tax balance, which lowers future RMDs and the taxes they force.
Net Investment Income Tax
Once MAGI passes \$200,000 (single) or \$250,000 (married), a 3.8% surtax can apply to investment income. A conversion can push you across that line.
Capital-gains stacking
Long-term gains can be taxed at 0% while your income is low. Extra ordinary income from a conversion can push those gains into the 15% or 20% brackets.
The five-year rule
Each conversion generally must season five years — and you must be 59½ — before the converted amount and its earnings come out entirely penalty- and tax-free.
State taxes and moves
Converting in a high-tax state costs more than waiting until after a move to a lower- or no-tax state. Timing conversions around relocation can matter.
Heirs and the survivor’s bracket
Roth assets pass to heirs income-tax-free. And when one spouse dies, the survivor files as single — at higher rates — so converting while both are alive can lock in today’s married brackets.
One more lever: market timing. Converting after a market decline moves more shares into the Roth per dollar of tax, so the recovery happens in a tax-free account. This tool is educational and does not capture every factor above — a qualified tax advisor can model your specific situation.
The break-even rate in action
Meet Susan. She is in the 35% bracket today, expects 24% in retirement, and is weighing a $100,000 conversion she would not touch for 20 years. The old rule of thumb says never convert into a lower future rate. The break-even method tells a different story.
Case study and break-even methodology credit: Vanguard, “A BETR Approach to Roth Conversions” (2025). Figures are hypothetical and for illustration only.
Thinking about a multi-year conversion plan?
A fiduciary advisor can map conversions across several years to manage brackets, IRMAA, and RMDs together. Start with a no-cost conversation.
Educational estimate only, not tax or investment advice. Consult a qualified tax professional before converting.