Roth Conversion Calculator

How to use this calculator

Enter the conversion amount (how much to move from Traditional IRA to Roth IRA), your current tax rate on that conversion, your expected retirement tax rate, years until retirement, and expected return.

Select whether you’re paying the conversion taxes from outside funds (your checking account or taxable brokerage) or from the IRA itself. Outside funds is almost always better.

The calculator shows your Roth value at retirement, the equivalent Traditional IRA after-tax value, tax owed now, and the net advantage or disadvantage of converting.

What a Roth conversion is

A Roth conversion moves money from a pre-tax retirement account (Traditional IRA, 401k, SEP IRA) to a Roth IRA. You pay ordinary income taxes on the converted amount in the year of conversion. After that, the money grows tax-free forever.

There are no income limits on conversions. A CEO earning $5M can convert $200,000 of IRA funds to a Roth IRA in the same year. The backdoor Roth IRA is a specific application of this rule for people whose income exceeds the Roth contribution limits.

When a Roth conversion makes sense

The break-even analysis is straightforward: convert when your current tax rate is lower than or equal to your expected retirement rate.

But there are non-obvious cases where conversion wins even at equal rates:

You expect RMDs to force withdrawals. Required Minimum Distributions at 73 force you to withdraw from your Traditional IRA whether you need the money or not. A large Traditional IRA means large RMDs, which push you into higher brackets and tax up to 85% of your Social Security. Converting before RMDs start removes that pressure.

Estate planning. Heirs who inherit a Roth IRA withdraw tax-free. Heirs who inherit a Traditional IRA owe ordinary income taxes on every dollar they withdraw. For people who want to leave money to children or grandchildren, a Roth conversion during their lifetime is a tax-efficient wealth transfer.

Low income years. A sabbatical year, early retirement before Social Security, a year with large business losses, or a year of significant deductions can temporarily put you in a lower bracket than usual. Converting in those years captures permanently lower tax rates.

The pro-rata rule: the biggest conversion complication

If you have any pre-tax Traditional IRA money, you can’t cherry-pick after-tax funds for a tax-free conversion. The IRS treats all your Traditional, SEP, and SIMPLE IRAs as one pool.

If you’re in the second scenario (10% after-tax) and convert $10,000, only $1,000 (10%) comes from after-tax funds. The other $9,000 is taxable.

The clean solution for a backdoor Roth: roll all pre-tax Traditional IRA funds into your employer’s 401k before doing the non-deductible contribution and conversion. Your employer’s 401k is a separate pool not subject to the pro-rata rule on IRA conversions.

Tax bracket management for conversions

The optimal conversion strategy is bracket-filling. Each year, convert enough to fill up your current tax bracket without crossing into the next one.

2025 single filer tax brackets:

• 10%: up to $11,925
• 12%: $11,926 to $48,475
• 22%: $48,476 to $103,350
• 24%: $103,351 to $197,300

If you’re single with $40,000 in other income and the 22% bracket tops at $103,350, you can convert up to $63,350 of IRA funds while staying entirely in the 22% bracket. Converting $63,350 at 22% costs $13,937 in taxes now, but all that converted amount grows tax-free.

Done consistently for several years before RMDs kick in at 73, this strategy can move a substantial portion of your Traditional IRA into a Roth while you’re still in relatively low brackets.

The 5-year rule on conversions

Each Roth conversion starts its own 5-year clock for the purpose of penalty-free withdrawal of the converted principal. This is separate from the 5-year clock on your original Roth IRA contributions.

If you’re under 59½ and convert $30,000 in 2025, you can’t withdraw that $30,000 without a 10% penalty until 2030. If you’re over 59½, the conversion 5-year rule doesn’t apply to withdrawals.

This matters most for people using Roth conversions as a bridge strategy in early retirement: convert now, access the converted funds penalty-free in 5 years when you need income before other accounts are accessible.

Paying conversion taxes: outside funds vs IRA funds

The math strongly favors paying from outside funds.

Outside funds scenario: Convert $50,000. Pay $11,000 tax from your savings account. The full $50,000 goes into the Roth IRA.

IRA funds scenario: Convert $50,000. The IRA pays the $11,000 tax. Only $39,000 enters the Roth IRA.

At 7% for 20 years, the difference: $50,000 grows to $193,484 vs $39,000 grows to $150,917. The outside-funds approach produces $42,567 more in tax-free retirement wealth.

If you’re under 59½ and pay the tax from IRA funds, the $11,000 used for taxes is also subject to a 10% early withdrawal penalty ($1,100 additional cost). Outside funds avoids that entirely.

Multi-year conversion strategy

Converting a large Traditional IRA in a single year creates a massive tax bill. The smarter approach: spread conversions over multiple years to stay in lower brackets.

A 60-year-old with $600,000 in a Traditional IRA and $30,000 in Social Security starting at 70 might convert $50,000/year for 10 years, paying 22% on each conversion ($11,000/year in taxes). Total tax on conversions: $110,000 over 10 years.

The alternative: take no conversions, let the $600,000 grow to roughly $1.18M by 73 (at 7%), and face RMDs starting at $44,500/year — pushing total income into 24-32% brackets for the rest of their life. Plus their heirs pay ordinary income taxes on inheritance.

The conversion strategy pays $110,000 in taxes over 10 years at 22%. The no-conversion strategy faces much higher lifetime taxes, spread across decades, at higher marginal rates.

Medicare premiums and IRMAA

A large Roth conversion in a given year increases your Modified Adjusted Gross Income (MAGI). Medicare uses a 2-year lookback to set Part B and Part D premiums.

2025 IRMAA thresholds (single filers, affecting 2027 premiums):

• Under $106,000: standard premium (~$185/month Part B)
• $106,000-$133,000: ~$259/month
• $133,000-$167,000: ~$370/month
• $167,000-$200,000: ~$480/month
• $200,000-$500,000: ~$591/month

A $100,000 Roth conversion that pushes you from $105,000 to $205,000 MAGI costs an extra $406/month in Medicare premiums two years later — $4,872/year.

Factor this into your conversion math if you’re 63-65. A conversion that looks beneficial ignoring Medicare might be break-even or worse after accounting for 2 years of elevated premiums.