🔄 401(k) to Roth Conversion: Tax Calculator (2026)

Estimate the ordinary income tax owed on converting pretax 401(k) or Traditional IRA funds to a Roth IRA — with 2026 bracket-stacking.

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Age
ESTIMATED TAX OWED ON THIS CONVERSION
$0
effective rate on taxable portion: 0%
Taxable Converted Amount
$0
Net Amount Landing in Roth IRA
$0
Marginal Bracket Before
0%
Marginal Bracket After
0%

How Roth Conversion Taxes Are Calculated

Converting pretax 401(k) or Traditional IRA money to a Roth IRA is a taxable event — the converted amount (minus any after-tax basis) is added to your taxable income for the year and taxed at your ordinary marginal rates, the same as if you'd earned that much extra income. This calculator uses the actual 2026 IRS bracket-stacking method, not a flat estimate, so it correctly shows when part of a large conversion spills into a higher bracket.

2026 Federal Tax Brackets Used

RateSingleMarried Filing Jointly
10%$0 – $12,400$0 – $24,800
12%$12,400 – $50,400$24,800 – $100,800
22%$50,400 – $105,700$100,800 – $211,400
24%$105,700 – $201,775$211,400 – $403,550
32%$201,775 – $256,225$403,550 – $512,450
35%$256,225 – $640,600$512,450 – $768,700
37%Over $640,600Over $768,700

Source: IRS Revenue Procedure 2025-32, the official 2026 inflation-adjusted bracket figures.

Why Timing and Size Matter

Conversion Tax = TaxOn(Income Before + Taxable Converted Amount) − TaxOn(Income Before)

Because conversion income stacks on top of your other income, converting a large amount in one year can push a meaningful chunk of it into a much higher bracket than converting smaller amounts over several years would. Many people strategically convert in years with unusually low income — such as between retirement and when Social Security or RMDs begin — to fill up lower brackets at a cheaper rate.

⚠️ Important: This calculator estimates federal ordinary income tax only — it doesn't include state income tax, the Net Investment Income Tax, or how a large conversion could affect other income-based thresholds (like IRMAA Medicare premiums or ACA subsidy cliffs). Roth conversions are also irrevocable since 2018 — there's no recharacterizing your way out once it's done. Talk to a CPA before converting a large amount.

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❓ Frequently Asked Questions

How is the tax on a 401(k)-to-Roth conversion calculated?
The taxable portion of your conversion is added on top of your other taxable income for the year and taxed at your marginal ordinary-income tax rates — not a flat rate. This means a large conversion can push part of the converted amount into a higher tax bracket than your regular income alone would reach, a process called bracket-stacking.
Is there an income limit on Roth conversions?
No. Unlike direct Roth IRA contributions, which phase out above certain income levels, Roth conversions have no income limit — anyone with a pretax 401(k) or Traditional IRA balance can convert it to a Roth IRA regardless of income.
What is the pro-rata rule, and does it apply to 401(k) conversions?
The pro-rata rule normally requires IRA conversions to be taxed proportionally across all pretax and after-tax dollars held in your IRAs combined. For a direct 401(k) rollover specifically, IRS Notice 2014-54 allows many plans to split a single distribution — sending the pretax portion to a Traditional IRA and the after-tax portion directly to a Roth IRA — which can avoid pro-rata taxation entirely if your plan supports it.
What happens if I have my taxes withheld from the conversion instead of paying separately?
If you have tax withheld from the converted funds rather than paying the tax from outside savings, less money actually lands in your Roth IRA, and the withheld amount is treated as a distribution to you — meaning it can trigger the 10% early-withdrawal penalty if you're under age 59½, on top of the income tax already owed.
Can I undo (recharacterize) a Roth conversion?
No. The Tax Cuts and Jobs Act eliminated the ability to recharacterize (undo) a Roth conversion starting with the 2018 tax year. Once you convert, the decision is permanent, so it's worth confirming the tax impact before converting rather than after.

🏆 About This Tool — Accuracy & Trust

🔒 Data Privacy: All calculations run entirely within your browser using JavaScript. Nothing you enter here is ever transmitted to our servers, stored, sold, or shared.

📐 Accuracy Note: Tax brackets are sourced from IRS Revenue Procedure 2025-32 for the 2026 tax year. Results estimate federal ordinary income tax only; consult a CPA for state tax and your complete financial picture before converting.

📅 Last Updated: October 2026.

Created and maintained by , founder of Your Calculator Hub · Last updated . How we build and check our calculators. Results are estimates for general information, not professional advice.