Roth Conversion Calculator: Tax Cost and Break-Even for 2026
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A Roth conversion is taxed as ordinary income in the year you convert. The federal tax is the tax on (income + conversion) minus the tax on income alone. Converting $25,000 on top of $85,000 of taxable income as a single filer adds $5,586 in 2026, an effective rate of 22.3%.
Converting $25,000 on top of $85,000 of taxable income (single) adds about $5,586.00 of federal tax. If your retirement rate is 22%, converting leaves you about $276 behind after 20 years. It pays off only if your later rate is above 22.3%.
How your conversion fills the tax brackets
| Bracket rate | Income range | Converted in this bracket | Federal tax |
|---|---|---|---|
| 22% | $50,400 to $105,700 | $20,700.00 | $4,554.00 |
| 24% | $105,700 to $201,775 | $4,300.00 | $1,032.00 |
Only the part of the conversion that lands in each bracket is taxed at that rate.
Tax cost at different conversion sizes
| Convert | Federal tax | Effective rate | Top bracket |
|---|---|---|---|
| $5,000 | $1,100 | 22.0% | 22% |
| $10,000 | $2,200 | 22.0% | 22% |
| $15,000 | $3,300 | 22.0% | 22% |
| $20,000 | $4,400 | 22.0% | 22% |
| $25,000 | $5,586 | 22.3% | 24% |
| $30,000 | $6,786 | 22.6% | 24% |
| $35,000 | $7,986 | 22.8% | 24% |
| $40,000 | $9,186 | 23.0% | 24% |
| $45,000 | $10,386 | 23.1% | 24% |
| $50,000 | $11,586 | 23.2% | 24% |
Show the steps
- Tax on your income alone: $13,412.00 (top bracket 22%).
- Tax on $85,000 + $25,000 = $110,000: $18,998.00.
- The difference is the federal tax on the conversion: $18,998.00 − $13,412.00 = $5,586.00.
- Growth factor: (1 + 6.00%)^20 = 3.2071.
- Without converting, the money is taxed at 22% later: $25,000 × 3.2071 × (1 − 22%) = $62,539.14.
- Converting costs $5,586.00 now. In 20 years’ dollars that is $17,915.06, and the Roth holds $80,178.39 tax-free. Net advantage: $17,639.25 − $17,915.06 = −$275.81.
When does a conversion pay off?
Advantage = (amount × later rate − tax paid now) × growth factor
It is positive when your retirement tax rate is higher than the effective rate you pay on the conversion.
- Uses the 2026 federal brackets (Revenue Procedure 2025-32). Taxable income is after your standard or itemized deduction.
- Does not model Medicare IRMAA surcharges, the loss of ACA premium credits, or taxes on Social Security, all of which can make a large conversion cost more.
- Each Roth conversion has its own 5-year clock for penalty-free withdrawals before 59½. If you hold other pre-tax IRAs, the pro-rata rule taxes the conversion partly as a mix of pre-tax and after-tax money.
Estimates for planning and learning, not financial, tax, legal or medical advice. Check figures with your lender, tax preparer or doctor before you act.
About this calculator
A Roth conversion moves money from a traditional IRA or 401(k) into a Roth IRA. You pay income tax on the amount you convert now, and in return the money grows tax-free and comes out tax-free later. People convert to smooth their taxes over many years, to reduce future required minimum distributions, or to leave tax-free money to heirs.
The tax cost depends on your other income. Each dollar you convert stacks on top of your taxable income and is taxed at the bracket it lands in. A small conversion may stay in the 22% bracket, while a large one can spill into 24% or 32%. This calculator uses the 2026 federal brackets, shows exactly which brackets your conversion fills, and tells you how much room you have left before the next rate begins.
It then compares converting with leaving the money in the IRA, using your expected return and your expected tax rate in retirement. The break-even is simple: converting pays off when your tax rate later is higher than the effective rate you pay on the conversion.
How to use it
- Choose your filing status and enter your taxable income for the year, after the standard deduction or your itemized deductions.
- Enter the amount you are thinking of converting, and your state tax rate if your state taxes IRA income.
- Set the number of years before you would take the money out, your expected yearly return and the tax rate you expect in retirement.
- Choose whether you will pay the tax from savings outside the IRA or from the conversion. Paying from outside keeps more money in the Roth, which usually works out better.
- Read the tax, the room left in your bracket and the advantage. Try different amounts to find a size that fits a bracket.
Fill a bracket instead of guessing
A common strategy is to convert just enough each year to fill your current bracket. If you are single with $85,000 of taxable income, the 22% bracket runs up to $105,700, so you could convert $20,700 and stay at 22%. Going beyond that taxes the extra at 24%.
Worked example
A single filer has $85,000 of taxable income and converts $25,000. The first $20,700 lands in the 22% bracket and costs $4,554. The remaining $4,300 lands in the 24% bracket and costs $1,032. The total federal tax is $5,586, or 22.3% of the conversion. If the filer expects a 24% rate in retirement, the conversion is worth it. At a 22% rate it is slightly behind.
What this calculator does not include
- Medicare IRMAA: a higher income can raise your Part B and Part D premiums two years later.
- ACA subsidies: a conversion counts as income and can reduce premium credits.
- Social Security: more income can make more of your benefit taxable.
- Other pre-tax IRAs: the pro-rata rule treats the conversion as a mix of pre-tax and after-tax money.
The 5-year rules
Each conversion has its own five-year clock. If you take converted money out within five years and you are under 59½, you may owe a 10% penalty on it. After 59½ the penalty does not apply to converted amounts, but earnings still need the Roth account to be at least five years old to come out tax-free.
Why pay the tax from outside the IRA
When you use outside savings for the tax, the whole conversion goes into the Roth and keeps growing tax-free. When you take the tax out of the conversion, you move less into the Roth. The math is close, but paying from outside generally gives the Roth more room to grow, and it is the assumption most planners prefer.
Sources
Quick check: test yourself
You convert 20,000 from a traditional IRA to a Roth IRA and pay 22% tax on it. How much tax do you owe?
Correct answer: $4,400. 20,000 × 22% = 4,400. The conversion is added to your taxable income in the year you convert.
When is a Roth conversion most likely to pay off?
Correct answer: When your tax rate in retirement is higher than the rate you pay on the conversion. You pay tax now to avoid tax later. That works best if the later rate is higher.
A single filer has 85,000 of taxable income. In 2026 the 22% bracket ends at 105,700. How much can they convert and stay in the 22% bracket?
Correct answer: $20,700. 105,700 − 85,000 = 20,700.
Pick an answer for each question.
Common questions
How is a Roth conversion taxed?
The amount you convert from pre-tax money is added to your ordinary income for the year and taxed at your bracket rates. Any part that is already after-tax, such as non-deductible contributions, is not taxed again.
How much should I convert each year?
A common approach is to convert enough to fill your current bracket without spilling into the next one. This calculator shows the room left in your bracket so you can pick that amount.
Is it better to pay the tax from the IRA or from savings?
Paying from savings outside the IRA is usually better, because the whole amount moves into the Roth and keeps growing tax-free. Paying from the IRA also counts as a distribution and can bring a 10% penalty if you are under 59½.
Does a conversion affect Medicare premiums?
It can. The extra income raises your modified adjusted gross income, and income two years earlier is used to set Medicare IRMAA surcharges.
Can I undo a Roth conversion?
No. Since 2018 the IRS no longer allows you to recharacterize a Roth conversion. Plan the amount carefully before you convert.
When does a Roth conversion not make sense?
When you expect a lower tax rate in retirement than the rate you would pay now, when the tax would push you into a much higher bracket, or when you would have to use the IRA money itself to pay the tax and are under 59½.
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