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Roth conversion calculator

Find the tax on converting a traditional IRA or 401(k) to a Roth, and compare its after-tax value in the future with not converting.

By the Calcist team · Checked against known answers · Updated October 27, 2026

Data: tax year 2026 · Source: IRS Rev. Proc. 2025-32 · Last reviewed October 2026

Private: calculated on your device. Nothing you type is sent anywhere.

Estimates for planning, not financial, tax or legal advice. Figures use US rules unless the page says otherwise.

Next: See the full-year picture with the income tax calculator, or plan withdrawals with the RMD calculator.

How it's calculated

Tax now = conversion × rate, or tax(income + conversion) − tax(income) with the 2026 brackets
Convert, tax paid from savings: conversion × (1 + r)ⁿ
Convert, tax paid from the conversion: (conversion − tax) × (1 + r)ⁿ
Don't convert: conversion × (1 + r)ⁿ × (1 − later rate) [+ the tax money invested outside, after tax on its growth]

"Use my income" adds the conversion on top of your taxable income and uses the 2026 federal brackets, so a large conversion that crosses into a higher bracket is taxed correctly. It's federal tax only; add state tax by entering a combined rate instead.

The break-even rate

Paying the tax from the conversion, converting wins only if your future tax rate is higher than the rate you pay now. Paying from savings, the break-even is a little lower, because money kept outside an IRA is taxed as it grows. That's why paying the tax from other savings usually makes a conversion work better.

Worked example

A single filer with $100,000 of taxable income converts $50,000. Taxable income becomes $150,000: $5,700 is taxed at 22% (up to $105,700) and $44,300 at 24%, so the conversion adds $11,886 of federal tax, an effective 23.77%.

Rules to know first

  • Conversions can't be undone. A Roth conversion made on or after January 1, 2018, can't be recharacterized (reversed). Once it's done, the tax is due.
  • The 5-year rule. Each conversion starts its own 5-year clock. If you're under 59½ and withdraw converted money within 5 years, the 10% additional tax can apply. Earnings come out tax-free only after your first Roth has been open 5 years and you're 59½.
  • Under 59½, pay from savings. Tax withheld from a conversion counts as an early distribution and can owe the 10% additional tax.
  • IRMAA. A conversion raises your income for that year. Medicare premiums are based on income from two years earlier, so a conversion at 63 or later can raise Part B and Part D premiums.
  • Other knock-on effects: the conversion can make more of your Social Security taxable, reduce credits and deductions that phase out with income, and trigger estimated tax payments.
  • Have nondeductible (after-tax) money in any traditional IRA? The pro-rata rule makes part of the conversion tax-free. This calculator treats it all as taxable.

Sources

How we checked this

Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:

  • Single, $100,000 taxable income, convert $50,000: $11,886 federal tax ✓
  • 24% now and later, tax from savings taxed 15% on growth: converting gains $5,165 ✓
  • Same: break-even future rate 21.33% ✓
  • Tax from the conversion, 22% now, 32% later: converting gains $19,348 ✓
  • Edge: tax from the conversion at equal rates: same result ✓

Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.

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Questions people ask

How much tax will I pay on a Roth conversion?

The converted amount is added to your taxable income, so it's taxed at your marginal rate, or several rates if it crosses brackets. A single filer with $100,000 of taxable income pays $11,886 of 2026 federal tax on a $50,000 conversion.

When can a Roth conversion pay off?

Mainly when you expect a higher tax rate on withdrawals later than you pay now, such as in a low-income year, early retirement before Social Security and RMDs, or before a large balance pushes you into higher brackets.

Can I undo a Roth conversion?

No. Recharacterizing a conversion was eliminated for conversions made after 2017.

What is the 5-year rule for conversions?

Each conversion has its own 5-year period. If you're under 59½ and take out converted money before it ends, the 10% additional tax can apply to that amount.

What if I pay the tax from the IRA?

It works, but paying from other savings moves more money into the Roth, and if you're under 59½ the amount withheld can also owe a 10% additional tax.

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