Roth Conversion Calculator: What Converting Costs and Where the Cliffs Are

01Your Conversion

A Roth conversion moves money from a traditional IRA into a Roth IRA. The amount converted counts as income for the year, so you pay income tax on it now, and qualified withdrawals from the Roth later are tax-free. Enter the conversion and your other income for the year; the calculator works out the tax with and without the conversion, and the difference is what the conversion costs.

02Room Left in Your Bracket

Bracket room is worked out by running the whole calculation again at higher amounts, so it counts the extra Social Security that becomes taxable and any senior deduction lost along the way, not just the gap in the bracket table. Brackets apply to taxable income after deductions; qualified dividends and long-term gains sit on top of ordinary income and are taxed at their own rates.

03Compare Amounts and Set a Tax Budget

Three conversion amounts side by side, worked out with everything else you entered above. The suggested amounts are the one you entered, the amount that fills your current federal bracket, and the most you can convert before your Medicare premiums move up a bracket (or the amount that fills the next federal bracket if Medicare does not apply). Change any of them.

04The Hidden Costs

Before and after the conversion

Tax on converting different amounts, split by cause. Each part is the extra tax as the effects are added in this order: the conversion at ordinary rates, then the Social Security it makes taxable, then the senior deduction it removes; capital gains, the investment income tax, state tax, the 10% additional tax and Medicare IRMAA are each measured on their own. IRMAA is a premium surcharge paid two years later, not a tax.

05Pay Now or Pay Later

A rough comparison, not a forecast. It follows the converted money for a number of years under the assumptions below and compares what you would have after tax either way: converting now and paying the tax now, or leaving the money in the traditional IRA and paying tax at a future rate when it comes out. When you pay the tax from money outside the IRA, that money would otherwise have stayed invested in a taxable account, so the comparison grows it too, from the year each cost is paid. Both sides follow the withdrawal rules: the 10% additional tax before 59½, the five-year clock on the conversion and the five-year test for tax-free Roth earnings.

06Rules to Know Before You Convert

The whole conversion is income this year. The taxable part of a conversion is added to your income for the year the money leaves the traditional IRA, and taxed at ordinary rates. The 10% tax on early withdrawals does not apply to the amount converted, even before 59½.

Each conversion has its own five-year clock. The clock starts on January 1 of the year you convert. Take converted money out before its five years are up while you are under 59½ and the taxable part of that conversion is subject to the 10% additional tax, unless an exception applies. Withdrawals come out of a Roth in a set order: your own contributions first, then conversions, oldest first, then earnings. Earnings are tax-free only once you are 59½ and five years have passed since your first Roth contribution or conversion.

It cannot be undone. Since the 2018 tax year a conversion cannot be recharacterized back into a traditional IRA. If the investments fall after you convert, the tax is still owed on the amount converted; converting in pieces over several years spreads that risk.

Take the year's RMD first. Once required minimum distributions have started (the year you turn 73 if you were born from 1951 to 1959, 75 if born in 1960 or later), the RMD for the year cannot be converted, and the first dollars out of the IRA in the year count as the RMD. Take it, then convert. The RMD Calculator works out the amount.

After-tax money is converted in proportion. If you have made nondeductible contributions, you cannot convert just the after-tax dollars. On Form 8606 the tax-free share of the conversion is your total basis divided by the year-end value of all your traditional, SEP and SIMPLE IRAs plus the year's distributions and conversions (the pro-rata rule). Basis belongs to the person whose IRA it is: each spouse has a separate basis and files a separate Form 8606, even on a joint return. Enter the basis of the person converting under Advanced settings to include it.

Tax withheld from the conversion is not converted. It counts as an ordinary distribution: taxable, and before 59½ usually subject to the 10% additional tax. Paying the tax from other savings keeps the whole amount growing in the Roth.

07The Federal Figures

Federal income tax brackets: the rate applies to taxable income above each line, after the standard or itemized deduction. A qualifying surviving spouse uses the married filing jointly brackets, capital gains lines and standard deduction, the single lines for Social Security, the senior deduction and Medicare, and the joint line for the investment income tax.

2026 brackets

Show married filing separately

2025 brackets (for reference)

Show married filing separately

Deductions and thresholds

2026: Rev. Proc. 2025-32 (IRB 2025-45), as amended by Public Law 119-21 (2025). 2025: Rev. Proc. 2024-40, standard deduction as amended by Public Law 119-21 (2025). The senior deduction, added by Public Law 119-21 in 2025, applies for 2025 to 2028 to anyone who is 65 or older by the end of the year and has a Social Security number on the return; married couples must file jointly. It is taken whether or not you itemize, and it shrinks by 6 cents for each dollar of modified adjusted gross income over the line, so it is gone at $175,000 ($250,000 joint).

Two thresholds that matter for conversions are fixed in the law and do not rise with inflation. Social Security benefits start to be taxable when your other income plus half your benefits passes $25,000 for single filers, heads of household and qualifying surviving spouses or $32,000 for married couples filing jointly, with the 85% tier above $34,000 and $44,000; for married people filing separately who lived together both lines are $0. The 3.8% net investment income tax applies to the smaller of your investment income or your modified adjusted gross income above $200,000 (single and head of household), $250,000 (married filing jointly or qualifying surviving spouse) or $125,000 (married filing separately).

08State Tax on a Conversion

Most states with an income tax tax a Roth conversion like other IRA income, at their own rates. The calculator adds the conversion to your other income, leaves Social Security out, and runs the state's 2026 rates, deductions and exemptions from the Paycheck Calculator with and without it. The difference is the state cost. For California the tables are 2025 figures (2026 not yet published). For a qualifying surviving spouse the state figure uses the state's married filing jointly tables.

What the calculator cannot model: many states exclude part of retirement income for older residents, give extra deductions or credits at 65, or tax part of Social Security benefits, and the rules differ in each state. Apart from the states in the table, the state figure assumes the full conversion is taxed and no Social Security is, so it can be too high where an exclusion applies and too low in a state that taxes benefits. County and city income taxes are not included. If you know how your state treats the conversion, use the state setting under Advanced settings.

09How the Calculator Works

The calculator figures your federal income tax for the year twice, without the conversion and with it, following the IRS worksheets: Social Security benefits made taxable under the Publication 915 rules; adjusted gross income; the larger of the standard deduction (with the extra amount at 65 or older or blind) or your itemized deductions; the senior deduction where it applies; then tax on ordinary income from the brackets, with qualified dividends and long-term capital gains taxed at 0%, 15% or 20% through the Qualified Dividends and Capital Gain Tax Worksheet. The 3.8% net investment income tax is figured on the taxable interest, dividends, capital gains, short-term gains, rent, royalties and other investment income entered; wages, pensions, IRA withdrawals, the conversion, Social Security, tax-exempt interest and the other taxable income line are not investment income. Medicare IRMAA uses the income-related premium tables from the Medicare IRMAA Calculator for the premium year two years after the conversion, or the latest year published if that one is not out yet, for each person who is 63 or older at the end of the tax year; its income is adjusted gross income plus tax-exempt interest. Not included: the alternative minimum tax, tax credits that shrink as income rises, the Marketplace premium tax credit, self-employment tax, the limits on itemized deductions that depend on income, and state taxes on Social Security or retirement income except as described above. The 10% additional tax on withheld tax depends on age on the date of the distribution (the IRA owner's age, which on a joint return is the age of the spouse whose IRA is converted): anyone 58 or younger at the end of the year is under 59½ on every day of the year and anyone 61 or older is past it, and for someone 59 or 60 at the end of the year the calculator asks. Nothing you enter leaves your browser.

The pro-rata rule follows Form 8606, lines 6 to 13, for the person whose IRA is converted: the basis divided by the year-end value of all of that person's traditional, SEP and SIMPLE IRAs plus the other IRA distributions entered plus the conversion. The same share of the other IRA distributions is tax-free. Pensions, annuities and 401(k) or 403(b) withdrawals are not part of it. When the calculator tries other conversion amounts (the chart, the bracket and Medicare solvers, the comparison), the year-end value is reduced by whatever more is converted, so the total in the IRAs stays the same.

Pay now or pay later: the conversion tax is counted as paid in the conversion year and the Medicare surcharge two years later, as one annual amount for that premium year; each grows in the outside account only from the year it is paid. Withdrawals are taken all at once after the number of years entered, at the age shown. The Roth side applies the ordering rules (conversion money comes out before earnings): converted money taken out before 59½ and before January 1 of the fifth year after the conversion owes the 10% additional tax on the part that was taxable when converted; earnings are tax-free only when the withdrawal is qualified, which the calculator treats as five years after January 1 of the first year any Roth IRA was funded and 59½ or older (death, disability and the first-home rule are not modelled); otherwise earnings are taxed at the future rate entered, plus 10% before 59½. The traditional side owes the future rate on the taxable part plus 10% before 59½. The common exceptions to the 10% additional tax, such as disability or a series of substantially equal payments, are not modelled. Any Roth contributions or older conversions you already have would come out before this money; they are left out.

State early-distribution penalties on tax withheld before 59½, such as California's 2.5%, are not modelled.

10Questions People Ask

11Sources

• IRS Rev. Proc. 2025-32 (Internal Revenue Bulletin 2025-45): 2026 tax brackets, standard deduction, capital gains thresholds
• IRS IR-2025-103: inflation adjustments for tax year 2026
• IRS Rev. Proc. 2024-40: 2025 capital gains thresholds and additional standard deduction
• IRS: Federal income tax rates and brackets (2025)
• IRS: One, Big, Beautiful Bill Act deductions for working Americans and seniors (FS-2025-03)
• IRS Schedule 1-A, Part V: enhanced deduction for seniors
• 26 U.S.C. 151(d)(5)(C): deduction for seniors
• IRS Publication 915: Social Security and equivalent railroad retirement benefits
• 26 U.S.C. 86: taxation of Social Security benefits
• IRS Instructions for Form 8960: net investment income tax
• IRS: Questions and answers on the net investment income tax
• IRS Publication 590-A: Contributions to IRAs (conversions)
• IRS Publication 590-B: Distributions from IRAs (five-year rule, early distributions)
• IRS Instructions for Form 8606: nondeductible IRAs and conversions
• IRS: Retirement plans FAQs regarding IRAs (recharacterization)
• IRS Topic 557: Additional tax on early distributions
• 26 U.S.C. 408A: Roth IRAs (conversions, five-year period, no recharacterization)
• 26 CFR 1.408A-4: converting to a Roth IRA (required minimum distributions cannot be converted)
• 26 CFR 1.408A-6: Roth IRA distributions (qualified distributions, the five-year periods, the 10% tax on converted amounts, ordering rules)
• 26 U.S.C. 72(t): 10% additional tax on early distributions, and the age 59 1/2 exception (on or after the date the person reaches 59 1/2)
• IRS Form 8606, Part I lines 6 to 13: the pro-rata calculation (year-end value, distributions and conversions)
• 26 U.S.C. 408(d)(2): all of a person's IRAs treated as one contract, valued at the close of the year
• 42 U.S.C. 1395r(i)(4): Medicare income-related premiums use income from the second year before the premium year
• Pennsylvania Department of Revenue, 2025 PA-40 instructions, line 1a
• Illinois Department of Revenue, Pub-120 Retirement Income
• Mississippi Code 27-7-15(4)(ff): amounts converted to a Roth IRA excluded from gross income
• State income tax tables: the DaveManuel.com Paycheck Calculator data, checked October 21, 2026, from each state's revenue department
• CMS: 2026 Medicare Parts B Premiums and Deductibles
• CMS: Medicare Part D 2027 National Average Monthly Bid Amount Information (July 28, 2026)
• 2026 Medicare Trustees Report

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