How much tax will I owe on a Roth conversion?

The taxable portion of a Roth conversion is added to your ordinary income for the year and taxed at your marginal federal rate. If you have nondeductible basis tracked on Form 8606, that portion is recovered tax-free pro-rata across all your traditional, SEP, and SIMPLE IRAs under IRC section 408(d)(2). For 2026, ordinary income brackets run 10 percent (up to $12,400 single / $24,800 MFJ), 12 percent, 22 percent, 24 percent, 32 percent, 35 percent, and 37 percent at the top (above $640,600 single / $768,700 MFJ). A $50,000 conversion with no basis stacked on top of $100,000 of ordinary MFJ income is fully taxed across the 22 and 24 percent brackets, generating about $11,000 to $12,000 in additional federal tax.

What is the pro-rata rule for Roth conversions?

IRC section 408(d)(2) requires that all your traditional, SEP, and SIMPLE IRAs be aggregated into a single combined balance for purposes of determining the taxable portion of any distribution or conversion. The taxable portion equals the conversion amount multiplied by the pre-tax fraction (total pre-tax balance divided by total combined IRA balance). The non-taxable portion equals the conversion multiplied by the basis fraction (Form 8606 total basis divided by total combined balance). You cannot designate a specific IRA or specific dollars as the conversion source for tax purposes. The pro-rata measurement uses the December 31 balance of all traditional, SEP, and SIMPLE IRAs in the year of conversion.

Are there income limits on Roth conversions in 2026?

No. Roth conversion income limits were permanently eliminated by the Tax Increase Prevention and Reconciliation Act of 2005 (TIPRA), effective starting January 1, 2010. Any taxpayer with a traditional, SEP, or SIMPLE IRA can convert any amount in any tax year regardless of MAGI. Married Filing Separately filers can also convert (the prior MFS bar was lifted at the same time). Roth conversion income is excluded from MAGI for the purpose of determining your direct Roth IRA contribution phase-out under IRC section 408A(c)(3)(B), but it is included in MAGI for IRMAA Medicare premiums, ACA premium tax credit, the net investment income tax, and the Saver's Credit AGI cap.

What is the 5-year rule for Roth conversions?

IRC section 408A(d)(2) imposes a 5-year holding period for tax-free withdrawal of converted amounts. Each Roth conversion starts its own 5-year clock, separate from the 5-year clock for Roth contributions. The clock starts on January 1 of the year of the conversion. If you withdraw the converted principal before the 5-year mark and before reaching age 59 1/2, the 10 percent early withdrawal penalty under IRC section 72(t) applies to the converted amount even though no income tax applies (the conversion was already taxed). After 5 years OR after reaching age 59 1/2, whichever comes first, the converted amount can be withdrawn penalty-free. Earnings on converted amounts follow the general 5-year rule from your first Roth IRA contribution, not the per-conversion clock.

Can I undo a Roth conversion in 2026?

No. The Tax Cuts and Jobs Act of 2017 eliminated recharacterization of Roth conversions effective for conversions completed after December 31, 2017. Once you convert, the conversion is permanent. The strategic implication is that you should run the tax math carefully before executing the conversion. Recharacterization of a contribution (not conversion) remains allowed under IRC section 408A(d)(6). For example, a Roth contribution made in error when MAGI was too high can be recharacterized as a traditional IRA contribution by the tax return due date including extensions, but a Roth conversion completed in 2026 cannot be reversed.

Should I do a Roth conversion in a low-income year?

Often yes. The classic Roth conversion sweet spot is a year with materially lower ordinary income than your expected retirement marginal rate. Common triggers: gap year between jobs, sabbatical, early retirement before Social Security and RMDs begin (typically ages 60 to 72), business loss year for the self-employed, or first year of marriage when filing jointly absorbs a large standard deduction. Convert just enough to fill the bracket below your expected retirement marginal rate. The math: if your current rate is 12 percent and your expected retirement rate is 22 percent, every dollar converted now saves 10 cents of future tax.

Does a Roth conversion affect my Medicare premiums?

Yes, two years later. The Income-Related Monthly Adjustment Amount (IRMAA) for Medicare Part B and Part D uses MAGI from two years prior. A 2026 Roth conversion increases your 2026 MAGI, which determines your 2028 Medicare IRMAA tier. The 2026 MAGI thresholds for IRMAA tiers begin at approximately $111,000 single / $222,000 MFJ. A conversion that pushes MAGI across an IRMAA bracket can add several hundred to several thousand dollars of Medicare premium per year for one calendar year. The IRMAA effect is one of the most overlooked costs of Roth conversions for taxpayers age 63 and older.

How is a Roth conversion reported on my tax return?

The custodian issues Form 1099-R with code 2 or 7 in box 7 (no early withdrawal penalty applies on the conversion itself) and the gross distribution in box 1. Report the gross amount on Form 1040 line 4a (IRA distribution) and the taxable amount on line 4b. If you have basis on Form 8606, complete Part II of Form 8606 to compute the taxable amount using the pro-rata calculation. Form 5498 from the receiving Roth IRA custodian (issued the following May) confirms the conversion contribution. Quarterly estimated tax may be needed in the conversion year to avoid an underpayment penalty under IRC section 6654.

What is a backdoor Roth and how is it different from a Roth conversion?

A backdoor Roth is a specific type of Roth conversion. The taxpayer makes a nondeductible contribution to a traditional IRA (no income limit applies to nondeductible contributions per IRC section 408(o)) and then converts the contribution to a Roth IRA. The strategy works for high-income taxpayers above the Roth IRA direct-contribution phase-out ($153,000 to $168,000 single, $242,000 to $252,000 MFJ in 2026). When the taxpayer has no other pre-tax IRA balances, the backdoor conversion is essentially tax-free because the basis fraction in the pro-rata rule equals 100 percent. When pre-tax balances exist, the conversion is taxed pro-rata across the combined balance. The standard fix is to roll pre-tax IRA balances into a current 401(k) plan first to isolate the after-tax basis.

Do I have to convert the full IRA balance at once?

No. Partial conversions are explicitly permitted and are the most common Roth conversion strategy. You can convert any dollar amount in any tax year, with no minimum. Partial conversions enable bracket management: convert just enough to fill the 12 or 22 percent bracket without crossing into 24 or 32 percent. Many taxpayers execute multi-year conversion plans converting $50,000 to $150,000 per year over a five-to-ten-year period to spread the tax cost and minimize bracket creep. Each annual partial conversion starts its own 5-year clock under IRC section 408A(d)(2). Use this calculator iteratively to model annual partial conversion amounts that stay within your target marginal bracket.

Roth Conversion Tax Calculator 2026 - Pro-Rata Rule, 5-Year Clock, Basis

Estimate the federal tax cost of a Roth IRA conversion in 2026. Models the pro-rata aggregation rule across all your traditional, SEP, and SIMPLE IRAs, recovers nondeductible basis from Form 8606, applies the 2026 marginal tax brackets from Rev. Proc. 2025-32, and computes the marginal tax cost of the conversion stacked on your other ordinary income.

Your Conversion Inputs

Tax Year

2026

2025

2026 brackets per IRS Rev. Proc. 2025-32 (IR-2025-103, October 2025). 2025 brackets per Rev. Proc. 2024-40 with OBBBA standard-deduction increase.

Filing Status

MFS uses single brackets through 22 percent then narrower thresholds. Calculator uses the official MFS schedule from Rev. Proc. 2025-32.

Other Ordinary Income ($)

Wages, self-employment net earnings, taxable interest, ordinary dividends, pension, taxable Social Security, and any other ordinary income before the conversion. Excludes long-term capital gains and qualified dividends (those follow the LTCG schedule).

Deduction Method

Standard Deduction

Itemize

Standard deduction TY 2026: $16,100 single / MFS, $32,200 MFJ, $24,150 HOH (Rev. Proc. 2025-32). Itemized requires manual entry below.

Itemized Deduction Total ($)

Sum of Schedule A line 17. Most taxpayers use standard deduction; itemize if your SALT, mortgage interest, charitable, and medical exceed the standard amount for your filing status.

Roth Conversion Amount ($)

Gross dollar amount you plan to convert from traditional, SEP, or SIMPLE IRA to Roth IRA in the tax year. Partial conversions allowed; no minimum.

Combined Pre-Tax IRA Balance Dec 31 ($)

Total Dec 31 balance of ALL your traditional, SEP, and SIMPLE IRAs (per IRC section 408(d)(2)). Includes the dollars being converted. Excludes Roth IRA, 401(k), 403(b), and inherited IRAs (separate aggregation).

Nondeductible Basis (Form 8606) ($)

Cumulative nondeductible contributions across all your traditional IRAs, tracked on Form 8606 line 14. If you have never made a nondeductible contribution, enter 0. Backdoor Roth users will have this figure.

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Enter your details
to estimate your Roth conversion tax cost

Item	2026	2025	Status
Conversion income limit	None	None	Confirmed
Standard deduction (single / MFS)	$16,100	$15,750	Confirmed
Standard deduction (MFJ / QSS)	$32,200	$31,500	Confirmed
Standard deduction (HOH)	$24,150	$23,625	Confirmed
10 percent ceiling - single	$12,400	$11,925	Confirmed
12 percent ceiling - single	$50,400	$48,475	Confirmed
22 percent ceiling - single	$105,700	$103,350	Confirmed
24 percent ceiling - single	$201,775	$197,300	Confirmed
32 percent ceiling - single	$256,225	$250,525	Confirmed
35 percent ceiling - single	$640,600	$626,350	Confirmed
37 percent floor - MFJ	$768,700	$751,600	Confirmed
Recharacterization of conversion	Prohibited	Prohibited	Confirmed
Pro-rata aggregation rule (§408(d)(2))	Active	Active	Confirmed
Per-conversion 5-year clock (§408A(d)(2))	Active	Active	Confirmed

Bracket	Single / MFS	MFJ / QSS	HOH
10%	$0 - $12,400	$0 - $24,800	$0 - $17,700
12%	- $50,400	- $100,800	- $67,450
22%	- $105,700	- $211,400	- $105,700
24%	- $201,775	- $403,550	- $201,775
32%	- $256,225	- $512,450	- $256,225
35%	- $640,600	- $768,700	- $640,600
37%	over $640,600	over $768,700	over $640,600

Roth Conversion Tax Calculator 2026

Quick Facts: 2026 Roth Conversion Numbers

How This Is Calculated

Step 1: Determine the Pro-Rata Taxable Fraction Confirmed

Step 2: Compute Adjusted Gross Income With Conversion Confirmed

Step 3: Subtract Deduction Confirmed

Step 4: Apply 2026 Marginal Brackets Confirmed

Step 5: Marginal Tax Cost of Conversion Confirmed

Assumptions

Real-World Examples

Practitioner Insight (LMN Tax Inc.)

When This Estimate May Not Apply

Frequently Asked Questions

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