Roth conversion calculator

How much extra federal tax the conversion adds this year, how much of the 12% / 22% / 24% bracket is left, and whether MAGI crosses a Medicare IRMAA cliff two years later. Brackets from Rev. Proc. 2025-32. IRMAA floors from the CMS 2026 table — a conversion this year hits IRMAA two years out, and those floors will be higher. Read the conversion primer first. This is not the Roth vs traditional contribution widget.

Quick answer: This calculator estimates the extra federal tax a Roth conversion adds this year, the room left in the brackets the page labels, and whether MAGI crosses an IRMAA cliff. The bracket and IRMAA figures are the ones already printed on the page.

Filing status Taxable income before conversion MAGI before conversion Conversion amount this year

Taxable income is Form 1040 taxable, after the standard or itemized deduction. MAGI for IRMAA is AGI plus tax-exempt interest. They are not the same number.

People on Medicare two years from now Under age 59½ this year? State income tax % (your rate, not a scrape) Other net investment income (NIIT flag)

A conversion is ordinary income, not NII. It can still pull existing NII over the $200k / $250k NIIT MAGI floor (IRC §1411, not indexed).

2026 conversion

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Federal tax uses 2026 ordinary tables (Rev. Proc. 2025-32). IRMAA extra is Part B + Part D monthly surcharges × 12 × people, from the CMS 2026 table, labeled as a stand-in for the lookback year. Prefill is the worked slice in NOTES: single, taxable $84,000, MAGI $100,000, convert $21,700 to the top of 22%. Sequence: tax-efficient withdrawals. Cliffs only: IRMAA MAGI room. Backdoor is a different tool: backdoor Roth.

What this means for you

What this means for you: the tax is this year's cost of moving pre-tax dollars to Roth. Room in a bracket is how much more you can convert before the next rate in this model. IRMAA uses a two-year lookback, so this year's MAGI prices premiums later, not this month.

How to use this calculator

Open the Roth conversion calculator and keep the sample numbers or replace them with your own. The result updates as you type.
Read the headline figure first, then the breakdown or chart under it.
Use Copy share link if you want those inputs in the URL. The page is an educational estimate, not a filing, approval, or recommendation.

FAQ

Does a conversion tax the whole balance?

It taxes the conversion amount at ordinary rates in this model, stacked on the other income you typed.

What is bracket room?

The distance from your taxable income to the top of the bracket the page is measuring. Filling it is not advice to convert.

When does IRMAA show up?

The page uses the published cliffs it labels. Premiums look back two years, so a conversion this year does not change this month's Medicare bill.

Educational, not financial advice. Page updated October 24, 2026 — no tax, limit, or rate figure was changed in this review.