Roth Conversion Calculator: How Much to Convert in 2026

Quick answer: when a Roth conversion pays off

A Roth conversion moves money from a traditional IRA (or 401(k)) to a Roth IRA. You pay income tax on it now, at your current rates, and qualified withdrawals later are tax-free (IRC §408A). It pays off when the rate you pay today is lower than the rate you'd pay when you withdraw. Paying the tax from savings lets the whole amount grow tax-free in the Roth and, before 59½, avoids a 10% tax. Low-income years, such as after you retire and before Social Security and required minimum distributions start, are the classic window.

The catch is that your rate on a conversion is often higher than your bracket. The calculator works out the real rate, counting Social Security, the senior deduction, Medicare premiums and state tax.

How much can I convert and stay in my bracket?

"Filling your bracket" means converting just enough to reach the top of your current bracket. The tops for 2026 are in taxable income, after deductions (Rev. Proc. 2025-32):

Start from your taxable income, not your gross income. Our tax bracket calculator shows how far you are from the next bracket. For retirees on Social Security, the simple subtraction overstates the room, because each converted dollar can also make Social Security taxable.

Your true rate on a conversion

Example: a single 67-year-old with $30,000 of Social Security and $20,000 of pension income in 2026. Subtracting today's taxable income from the top of the 12% bracket suggests about $49,200 of room. In fact, filling the 12% bracket takes only $29,049, because the conversion makes $20,150 of Social Security taxable as well. The tax is $5,680, 19.6% of the conversion, not 12%, and the next $1,000 would be taxed at 22.7%.

• Social Security (the "tax torpedo"): up to 85% of benefits become taxable as "provisional income" (other income plus half your benefits) rises past $25,000 single or $32,000 joint. Inside that range, each converted dollar can add 50 or 85 cents of taxable income (IRS Pub. 915). For the withdrawal side of the same math, see the Roth vs traditional 401(k) calculator.
• The senior deduction (2025–2028): $6,000 per person 65 or older, reduced by 6% of income over $75,000 ($150,000 joint) (IRS). Converting inside that range raises your rate by 6% of your bracket, or 12% for a couple.
• Capital gains and the 3.8% tax: a conversion sits under your long-term gains, so it can push them out of the 0% capital gains bracket, and raise income toward the $200,000 / $250,000 thresholds for the net investment income tax.

Medicare IRMAA: a 2026 conversion sets 2028 premiums

Medicare Part B and D premiums rise in steps for higher incomes (the income-related monthly adjustment amount, IRMAA). Social Security uses your tax return from two years earlier, so income in 2026 sets 2028 premiums (SSA). The tiers are cliffs: $1 over a line costs the full step for the year, for each spouse on Medicare. Start watching from age 63.

Source: CMS. Modified AGI = adjusted gross income plus tax-exempt interest. The tiers for 2028 aren't known yet; they're adjusted for inflation. A Roth conversion isn't a "life-changing event" for an appeal (20 CFR 418.1205), though retiring is.

Marketplace coverage: the 400% cliff

Retiring before 65 on a Marketplace plan? The conversion counts as income for the premium tax credit (HealthCare.gov). With the extra credits of 2021–2025 gone, there's no credit at all above 400% of the poverty line in 2026: about $62,600 for one person or $84,600 for two. A conversion that crosses that line can cost thousands in lost credit; the calculator warns you.

State tax on conversions

Many states tax a conversion as ordinary income; some exclude part of retirement income, such as New York's $20,000 pension and annuity exclusion from 59½, which covers conversions. States without an income tax don't tax it, and some exempt it: Illinois lets you subtract IRA amounts converted to a Roth (IL Pub. 120), Pennsylvania generally doesn't tax a completed conversion, Mississippi excludes conversions, and Iowa exempts retirement income, including conversions, from age 55 (or if disabled) (Iowa DOR). Moving to a lower-tax state before converting can save a lot; check the new state's rules.

Pay the tax from savings or from the IRA?

From savings, if you can. Paying from the IRA shrinks what lands in the Roth, and before 59½ the money used for tax is a withdrawal with a 10% additional tax. For a 50-year-old with $80,000 of income filling the 22% bracket, converting $41,799 costs $9,196 in federal tax; taken from the IRA, that adds about $920 of 10% tax and only $31,684 reaches the Roth.

After-tax money in your IRA: the pro-rata rule

If you made nondeductible IRA contributions, part of every conversion is tax-free, but you can't pick which dollars you convert. The tax-free share is your total after-tax basis divided by the year-end value of all your traditional, SEP and SIMPLE IRAs plus the amount converted (Form 8606). Money in a 401(k) doesn't count, so rolling pre-tax IRA money into a workplace plan first can raise the tax-free share.

A multi-year conversion plan

Large balances are usually converted over several years, filling the same bracket each year, so required minimum distributions later (from 73, or 75 if you were born in 1960 or later) are smaller (IRS Pub. 590-B). The calculator's table repeats this year's conversion for up to 15 years, with the same income and brackets. Re-run it every year with your actual income.

Deadlines and the two 5-year rules

• December 31: a conversion counts in the year the money leaves the IRA; there's no April deadline. Leave time for processing.
• No undo: conversions can't be recharacterized (reversed) since 2018 (IRS).
• RMD first: at 73 or older, this year's required minimum distribution must come out before you convert, and it can't be converted.
• Estimated tax: a large conversion may need an estimated payment or more withholding to avoid an underpayment penalty.
• 5-year rule for conversions: each conversion has its own clock, starting January 1 of its year. Taking converted money out within 5 years before 59½ costs a 10% additional tax on it.
• 5-year rule for earnings: earnings generally come out tax-free only after 59½ (or death or disability, or up to $10,000 for a first home) and 5 years from your first Roth IRA contribution or conversion. Withdrawals come out in order: contributions, then conversions (oldest first), then earnings (Treas. Reg. 1.408A-6).

When a conversion is a bad idea

• Your rate now is higher than you expect in retirement (common in peak earning years).
• You'd have to pay the tax from the IRA, especially before 59½.
• You'll need the money within 5 years and you're under 59½.
• It would cross an IRMAA tier or the Marketplace 400% line by a small amount.
• You plan to leave the IRA to charity, or to heirs in a lower bracket than yours.

Common questions

Is there an income limit for Roth conversions?

No. Anyone can convert, at any income, since 2010. The income limits apply only to direct Roth IRA contributions.

When is the deadline for a 2026 Roth conversion?

December 31, 2026. Unlike IRA contributions, conversions can't be made for 2026 after the year ends.

Can I undo a Roth conversion?

No. Recharacterizing a conversion hasn't been allowed since 2018, so check the numbers first.

Do I pay a penalty on a Roth conversion?

Not on a direct conversion. But tax paid from the IRA before 59½ counts as a withdrawal with a 10% additional tax, and converted money taken out within 5 years before 59½ is also hit.

How much should I convert each year?

Often enough to fill your current bracket without crossing a Medicare IRMAA tier or the Marketplace 400% line. The calculator finds that amount.

Does a Roth conversion affect Social Security?

It doesn't reduce your benefits, but it can make more of them taxable this year, and it can raise Medicare premiums two years later.

Can I convert my 401(k) to a Roth?

Yes: many plans allow in-plan Roth conversions, or you can roll it to a Roth IRA when you leave. The tax works the same way.

Sources

1. 26 U.S. Code § 408A, Roth IRAs — Legal Information Institute, Cornell Law School. Accessed October 16, 2026.
2. 26 CFR 1.408A-6, Distributions (5-year rules and ordering) — Legal Information Institute, Cornell Law School. Accessed October 16, 2026.
3. Instructions for Form 8606, Nondeductible IRAs — Internal Revenue Service. Accessed October 16, 2026.
4. Publication 590-B, Distributions from IRAs — Internal Revenue Service. Accessed October 16, 2026.
5. Publication 915, Social Security and Equivalent Railroad Retirement Benefits — Internal Revenue Service. Accessed October 16, 2026.
6. Publication 6142: the enhanced deduction for seniors — Internal Revenue Service. Accessed October 16, 2026.
7. Revenue Procedure 2025-32 (2026 inflation adjustments) — Internal Revenue Service. Accessed October 16, 2026.
8. 2026 Medicare Parts A & B premiums and deductibles — Centers for Medicare & Medicaid Services. Accessed October 16, 2026.
9. Medicare premiums: rules for higher-income beneficiaries — Social Security Administration. Accessed October 16, 2026.
10. 20 CFR 418.1205, Life-changing events — Social Security Administration. Accessed October 16, 2026.
11. What to include as income — HealthCare.gov. Accessed October 16, 2026.
12. Publication 120, Retirement Income — Illinois Department of Revenue. Accessed October 16, 2026.
13. Retirement income tax guidance — Iowa Department of Revenue. Accessed October 16, 2026.

Research checked October 16, 2026. This is an estimate, not tax advice.