Roth Conversion Tax Calculator (2026)

See the extra federal income tax if you convert traditional, SEP or SIMPLE IRA dollars to Roth this year — ordinary 2026 brackets, standard deduction, optional pro-rata basis.

By The PiggyMath Editorial Desk Last updated August 14, 2026 ✓ Independently verified against published IRS figures

How this is calculated

Federal income tax is computed twice on 2026 ordinary brackets: once on other ordinary income after the standard deduction, and once after adding the taxable conversion. The difference is the extra tax. Taxable conversion is the full amount unless you enter after-tax basis; then the pro-rata rule uses basis ÷ IRA balances. Roth conversions are not net investment income (no 3.8% NIIT) and not self-employment income.

Worked example: single filer with $80,000 of other ordinary income and a $20,000 fully pre-tax conversion. Standard deduction $16,100. Tax without the conversion is tax on $63,900 taxable; tax with it is tax on $83,900. The extra is the conversion’s federal cost, and the tool shows how much room was left in the current band.

Income and conversion

Filing status

Other ordinary income this year ($)Wages, SE profit after the half-SE deduction, interest — before the conversion.

Amount converted to Roth ($)

Extra deductions beyond the standard ($)Itemized excess, deductible IRA, etc. Leave 0 to use only the 2026 standard deduction.

Year-end traditional / SEP / SIMPLE IRA balance ($)All those IRAs combined, including the converted dollars, for pro-rata.

After-tax basis in those IRAs ($)Form 8606 basis. $0 means the conversion is fully taxable.

Extra federal income tax on the conversion

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Tax with conversion

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Tax without conversion

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Taxable conversion

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Bracket room

Conversions are ordinary income, not capital gains

Moving pre-tax IRA dollars into a Roth is a taxable event on Form 1040. The converted amount (minus any recovered basis) is added to ordinary income. It does not get the 0/15/20% long-term capital-gain schedule, and it is not net investment income under §1411, so the 3.8% NIIT does not attach to the conversion itself. That is the opposite of selling Bitcoin or a brokerage stock — which is why this page is not a crypto calculator and does not reuse the capital-gains engine.

The IRA contribution calculator already on PiggyMath answers a different question: how much you may put in, and whether MAGI blocks a direct Roth contribution. A conversion of money that is already inside a traditional IRA has no annual contribution limit. The cost is tax this year in exchange for tax-free qualified withdrawals later. This page prices that tax with the same 2026 brackets and standard deduction used everywhere else on the site.

Filling a bracket vs jumping one

Because tax is stacked, converting just enough to finish the current band is often cheaper per dollar than converting an amount that spills into 24% or 32%. The “room before this conversion” line is the distance from taxable income (other ordinary income minus the standard deduction) to the top of that band. A $20,000 conversion when you have $8,000 of 12% room is not a 12% conversion — part of it is taxed at the next rate. The extra-tax figure already reflects that mix.

Pro-rata and the backdoor

If any of your traditional, SEP or SIMPLE IRAs hold after-tax basis (nondeductible contributions reported on Form 8606), you cannot convert only the basis. The IRS looks at all those IRAs together. Enter the combined year-end balance and the basis; the taxable slice is the conversion times (1 − basis/balance). A Solo 401(k) balance usually sits outside that fraction, which is why some people roll a SEP into a Solo 401(k) before a backdoor conversion. The contribution/backdoor helper lives on the IRA calculator; this page only prices the tax of the conversion itself.

What this estimate skips

State income tax, IRMAA Medicare surcharges, ACA premium-tax-credit MAGI, and the five-year recapture rules on converted dollars are out of scope. A trustee-to-trustee conversion is not an early distribution, so the 10% additional tax generally does not apply here. Recharacterizations of Roth conversions are no longer allowed. PiggyMath does not e-file and does not move IRA money.

Frequently asked questions

Is a Roth conversion taxed as ordinary income?

Yes. Pre-tax traditional, SEP and SIMPLE IRA dollars converted to Roth are included in ordinary income for the year. They are not capital gains and are not net investment income, so the 3.8% NIIT does not apply to the converted amount.

Does a conversion trigger the 10% early-distribution tax?

A trustee-to-trustee Roth conversion is not a distribution, so the 10% additional tax on early distributions generally does not apply. Taking cash out of the Roth within five years of the conversion can still be taxable or penalized — this page does not model that five-year rule.

What is the pro-rata rule?

If you have after-tax basis in any traditional, SEP or SIMPLE IRAs, each conversion is partly nontaxable. The taxable share is 1 minus (basis / year-end IRA balances). Employer plans such as a Solo 401(k) usually do not count in that fraction.

How is this different from the IRA contribution calculator?

The IRA page answers how much you may contribute and whether MAGI blocks a direct Roth. This page answers how much extra federal tax a conversion of existing pre-tax dollars would cost in 2026.

2026 figures are sourced in data/tax-constants-2026.json and listed with IRS/SSA links on Tax Constants 2026. Calculators read the mirrored values in assets/app.js (kept in sync by tools/verify_tax_constants.mjs). No Enrolled Agent or CPA has reviewed this page unless separately disclosed with credentials and a review date.

Sources

Every formula on this page is checked against an independent implementation before publication. How we check our math →