Converting pretax retirement savings into a Roth IRA can lock in today’s lower tax rates and prevent much larger tax bills when required withdrawals arrive. The 2026 inflation-adjusted numbers create a little extra room inside some brackets — for example, the top of the 12% band sits at $50,400 for single filers and $100,800 for married couples filing jointly, while the top of the 24% band for married filers is $403,550. With the 2026 standard deduction at $16,100 (single) and $32,200 (married filing jointly), a carefully timed conversion can move pretax dollars into a Roth without pushing you into the next marginal rate.
At its core a Roth conversion takes money from a traditional account and reports it as ordinary income for the year. The converted amount is taxable now but then grows tax-free inside the Roth and can be withdrawn tax-free after age 59½. The idea of filling a bracket is to convert just enough so your taxable income reaches — but does not exceed — the ceiling of the tax bracket you want to capture. One dollar beyond that line gets taxed at the next marginal rate, which can meaningfully increase your cost of conversion.
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Principles and mechanics
How conversions affect your tax picture
When you add a conversion to your tax return, it increases your adjusted gross income and therefore MAGI, which matters beyond income tax bills. Conversions are taxed at your marginal rate for the year, so the incremental tax equals the converted amount multiplied by that marginal percentage. Use the 2026 bracket ceilings and the appropriate standard deduction to calculate the exact room you have to each ceiling. Pay the tax from non-retirement funds so the maximum amount ends up in the Roth.
Which bracket should you target?
Choose your target based on where you expect to land in retirement, not just on today’s rates. Converting at 12% when you think you’ll be in the 22% or 24% later is usually advantageous. For many savers the clear planning anchors are the top of the 12% band and the top of the 24% band because the jumps beyond them (to 22% and 32%) are relatively steep. Remember that conversions can be done over multiple years to smooth tax impact and reduce the chance of triggering other income-based penalties.
Three practical scenarios
The low-income year: married filers on a sabbatical
Imagine a married couple with W-2 earnings of $90,000 and a household age in their mid-50s. After the $32,200 standard deduction, their taxable income before conversions is $57,800, leaving $43,000 of room before the 12% ceiling of $100,800. Converting that $43,000 would cost roughly $5,160 in federal tax at 12%. Stopping exactly at the bracket edge preserves the lower rate on every converted dollar; even a modest overshoot would immediately subject those extra dollars to a higher marginal rate.
A single filer between jobs
Consider a single taxpayer who had $35,000 of earned income for the year and takes the $16,100 standard deduction. Their taxable income sits at $18,900, leaving $31,500 of space up to the 12% ceiling at $50,400. Converting that block would create $3,780 of federal tax at 12%, compared with $6,930 if those dollars were taxed later at 22% — a near-term tax saving plus decades of potential tax-free growth inside the Roth.
Higher earners targeting the 24% band
Two high earners with combined taxable income near $287,800 (after the $32,200 married deduction) already sit in the 24% bracket. They can convert up to $115,750 and remain inside 24% before hitting 32% at the $403,550 threshold. That conversion would cost about $27,780 at 24%, but it effectively locks in an 8-percentage-point discount compared with a future 32% environment — roughly $9,260 in tax difference per converted block of $115,750, not including the long-term benefit of tax-free Roth growth.
Watch out for two income-triggered traps
Beyond income tax, raising MAGI through conversions can trigger extra costs. First, IRMAA surcharges on Medicare Part B and Part D rely on MAGI from two years earlier; for 2026, the first IRMAA surcharge begins for single filers with 2026 MAGI over $106,000 and married filers over $212,000. Second, marketplace subsidies under the ACA use MAGI for eligibility and phaseouts; a conversion that nudges you past a phaseout point can cause subsidy repayment that overwhelms any tax savings. Model both impacts before you convert.
Action checklist
Project your year-end taxable income early, select the bracket ceiling to target based on your expected retirement marginal rate, and estimate any IRMAA or ACA consequences if they apply to you. Execute conversions by December 31 and pay the resulting tax from non-retirement sources. Reassess annually: a single low-income year may be the best conversion opportunity you get. Also factor in the evolving RMD environment under SECURE 2.0, which raised the RMD start age to 73 for many and will move it to 75 for later cohorts; Roth 401(k)s are now treated more like Roth IRAs for RMD purposes, which changes long-term distribution planning. When in doubt, run detailed projections or consult a tax professional to confirm the math before pulling the trigger.