Roth Conversion Calculator 2026

Q: What is a Roth conversion and how is it taxed?

A Roth conversion moves money from a Traditional IRA to a Roth IRA. The converted amount is added to your ordinary income and taxed at your marginal rate. After conversion, future growth and qualified withdrawals are completely tax-free. There is no income limit on conversions.

Q: What is the pro-rata rule for Roth conversions?

The IRS treats all your Traditional, SEP, and SIMPLE IRAs as one pool. The non-taxable ratio equals your non-deductible basis divided by total IRA value. You cannot cherry-pick only after-tax dollars for conversion.

Q: How does a Roth conversion affect Medicare premiums (IRMAA)?

Medicare uses a 2-year lookback: 2026 income determines 2028 premiums. A large conversion can push you into a higher IRMAA tier, adding up to $578/month per person in surcharges. The thresholds are cliff-based — even $1 over triggers the full surcharge.

Q: Should I convert all at once or use a multi-year strategy?

For large IRA balances ($200K+), a multi-year bracket-filling strategy typically saves significant taxes. Convert just enough each year to fill a target bracket (e.g., 22% or 24%), avoiding higher marginal rates and potential IRMAA surcharges.

Converting $500K at once costs $170K in taxes. Spread it over 5 years and save $40K+. See your numbers.

Unlike Roth IRA contributions, there is no income limit for Roth conversions. Anyone can convert any amount.

Filing status

Your age

Under 59½? 5-year rule may apply.

Ordinary income (before conversion)

W-2, pensions, Social Security, other income

Traditional IRA balance

Amount to convert

Enter 0 to convert entire balance

Non-deductible basis in Traditional IRA

After-tax contributions (Form 8606). Triggers pro-rata rule.

SEP/SIMPLE IRA balance

Included in pro-rata calculation

State income tax rate

On Medicare (check IRMAA impact)

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2026 tax brackets (Rev. Proc. 2025-32 + OBBBA) · IRMAA 2026 (CMS) · Updated March 2026

How to Use This Calculator

Tab "Convert & Compare"

Enter your filing status, ordinary income (W-2, pensions, Social Security), and Traditional IRA balance. The calculator shows the federal tax cost of converting, your marginal and effective rates, and the net amount entering your Roth. Under "More options," add non-deductible basis (Form 8606) to trigger the pro-rata rule, SEP/SIMPLE IRA balances, state tax rate, and Medicare status for IRMAA warnings.

Tab "Multi-Year Strategy"

Instead of converting everything at once, fill a specific tax bracket each year. Choose a target bracket (12%, 22%, 24%, or 32%), set the projection period, and the calculator shows a year-by-year table with conversion amounts, taxes, and remaining balance. It compares your multi-year total tax against a lump-sum conversion — the difference is your savings from bracket-filling.

Tab "IRMAA Impact"

Medicare premiums jump at specific income cliffs — even $1 over can cost $1,000+/year extra. Enter your current MAGI and planned conversion to see which IRMAA tier you'd land in, the monthly surcharge increase, and how much less you'd need to convert to stay below the cliff. The 2026 tier table is shown for reference.

The Formulas

Tax on Roth conversion:
Taxable income (without conversion) = Ordinary income − Standard deduction
Taxable income (with conversion) = Ordinary income + Taxable conversion − Standard deduction
Conversion tax = Tax(with) − Tax(without)

2026 Standard deductions: $16,100 (Single), $32,200 (MFJ), $16,100 (MFS), $24,150 (HoH)

Pro-rata rule (Form 8606):
Non-taxable ratio = Non-deductible basis / (Total Traditional + SEP + SIMPLE IRA balances)
Taxable portion = Conversion amount × (1 − ratio)

Multi-year bracket-filling:
Conversion room = Bracket top − (Ordinary income − Standard deduction)
Annual conversion = min(Conversion room, Remaining IRA balance)
End-of-year balance = (Balance − Conversion) × (1 + Growth rate)

IRMAA surcharges (2026, per person/month):
Tier 0: ≤$109K single / ≤$218K MFJ → $0
Tier 1: $109K–$137K / $218K–$274K → +$95.70/mo
Tier 2: $137K–$171K / $274K–$342K → +$240.40/mo
Tier 3: $171K–$205K / $342K–$410K → +$385.00/mo
Tier 4: $205K–$500K / $410K–$750K → +$529.60/mo
Tier 5: >$500K / >$750K → +$578.00/mo

Federal tax brackets use the 2026 rates from IRS Revenue Procedure 2025-32, as amended by the One Big Beautiful Bill Act (OBBBA) which made TCJA's individual rates permanent. IRMAA uses a 2-year lookback: 2026 income affects 2028 Medicare premiums.

Example

Sarah — Retired Teacher in California, Age 63

Filing Single. Pension income $45,000/year. Traditional IRA $400,000 (no non-deductible basis). California state tax 9.3%. On Medicare.

Lump-sum: Federal tax$102,438

Lump-sum: State tax (9.3%)$37,200

Lump-sum: Total tax cost$139,638

Lump-sum: IRMAA impact+$530/mo (Tier 4)

Multi-year (5yr, fill 22%): Total tax~$81,300

Multi-year: IRMAA impact$0 (stays Tier 0)

Tax savings from multi-year~$58,000

By spreading her conversion over 5 years and filling only the 22% bracket, Sarah saved ~$58,000 in taxes and avoided IRMAA surcharges entirely. She shared the link with her financial advisor: "I almost converted everything at once — that would have cost me an extra $530/month in Medicare premiums alone."

Frequently Asked Questions

What is a Roth conversion and how is it taxed?▼

A Roth conversion moves money from a Traditional IRA (or other pre-tax retirement account) to a Roth IRA. The converted amount is added to your ordinary income for the year and taxed at your marginal federal (and state) rate. After conversion, future growth and qualified withdrawals from the Roth IRA are completely tax-free. There is no income limit on conversions — unlike Roth IRA contributions, anyone can convert regardless of income.

Is there an income limit for Roth conversions?▼

No. Since 2010, there is no income limit on Roth conversions. This is different from Roth IRA direct contributions, which phase out at $150,000–$165,000 (Single) and $236,000–$246,000 (MFJ) for 2025. This distinction is what makes the "backdoor Roth" strategy possible — you contribute to a Traditional IRA (no income limit for non-deductible contributions) and then convert to Roth.

What is the pro-rata rule for Roth conversions?▼

The IRS treats ALL your Traditional, SEP, and SIMPLE IRAs as one combined pool. You cannot "cherry pick" only after-tax dollars for conversion. The non-taxable ratio equals your total non-deductible basis divided by the total value of all these accounts (as of December 31). For example, if you have $20,000 in non-deductible basis and $200,000 total across all IRAs, only 10% of any conversion is tax-free. To avoid this, consider rolling pre-tax IRA money into an employer 401(k) before converting — employer plans are not included in the pro-rata calculation.

How does a Roth conversion affect Medicare premiums (IRMAA)?▼

Medicare uses a 2-year lookback: your 2026 income determines your 2028 Medicare premiums. A Roth conversion increases your MAGI, which can push you into a higher IRMAA tier. The surcharges are cliff-based — even $1 over a threshold triggers the full surcharge for that tier. At the highest tier (Tier 5), the combined Part B + Part D surcharge is $578/month ($6,936/year) per person. For married couples both on Medicare, double these amounts. This is a frequently overlooked cost of large one-time conversions.

Should I convert all at once or use a multi-year strategy?▼

For most people with large Traditional IRA balances ($200K+), a multi-year "bracket filling" strategy saves significant taxes. Instead of converting everything at once (which pushes into higher brackets), you convert just enough each year to fill up to a target bracket — typically 22% or 24%. The savings compound: lower marginal rates, potential IRMAA avoidance, and more money growing tax-free in the Roth. The ideal window is often between retirement and age 73 (when RMDs begin), when ordinary income is lowest.

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