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Roth Conversion Calculator 2025

Should you convert your Traditional IRA or 401(k) to a Roth? See your conversion tax, tax-free Roth growth, after-tax Traditional value, and the net benefit of converting.

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How the Roth Conversion Calculator Works

This calculator answers one question: are you better off converting pre-tax retirement money to a Roth now, or leaving it in a Traditional account? It models two scenarios side by side over the years you let the money grow. In the convert scenario, the amount is taxed today at your current marginal rate; what remains compounds tax-free inside the Roth and is never taxed again. In the don't convert scenario, the full pre-tax balance keeps growing in the Traditional account, but every dollar withdrawn in retirement is taxed at your expected future rate.

The headline figure is the net benefit of converting — the tax-free Roth value minus the after-tax Traditional value. Green means converting wins; red means waiting wins. You can also choose whether the conversion tax is paid from the converted amount or from outside funds, which materially changes the outcome because paying from outside lets the entire balance compound tax-free. Defaults reflect a common 2025 scenario, so the page is useful the moment it loads — just replace the numbers with your own.

Who Benefits Most From Converting

  • Early retirees in low-income years before Social Security and RMDs begin, who can convert at a temporarily low bracket.
  • People who expect higher future tax rates — either personally or because they believe rates will rise.
  • Savers with outside cash to pay the tax, so the entire balance compounds tax-free in the Roth.
  • High earners locked out of direct Roth contributions, who use the backdoor Roth strategy.
  • Those leaving money to heirs, since Roth accounts have no lifetime RMDs and pass tax-free to beneficiaries.
  • Anyone wanting to reduce future RMDs that could push them into higher brackets at 73.

Who Should Look Elsewhere

A Roth conversion is rarely worthwhile if you expect to be in a lower tax bracket in retirement than you are today — paying tax now at a high rate to avoid a lower rate later usually loses. It is also a poor fit if you cannot pay the conversion tax from outside funds, if you are under 59½ and may need the money within five years (the conversion five-year rule can trigger a 10% penalty), or if the conversion would push you into a much higher bracket or trigger Medicare IRMAA surcharges. People close to retirement with little time for tax-free growth to make up the upfront tax cost should be cautious, as should anyone with significant pre-tax IRA balances that complicate the pro-rata calculation. If you are simply deciding how much to contribute to a Roth versus a Traditional account this year, that is a different question than converting an existing balance.

Tax Implications of a Roth Conversion

A conversion is a fully taxable event in the year you do it: the converted amount is added to your ordinary income and taxed at your marginal rate — there is no special lower rate. A large conversion can push part of the amount into a higher bracket, so partial conversions that "fill up" your current bracket are often smarter. The added income can also raise your Medicare Part B and D premiums two years later through IRMAA, increase the taxable portion of your Social Security, and affect income-based credits and deductions.

If you hold both pre-tax and after-tax money in any IRA, the pro-rata rule determines what fraction of the conversion is taxable — you cannot cherry-pick only the after-tax dollars. You generally owe the tax for the conversion year and may need estimated tax payments to avoid an underpayment penalty. Conversions are permanent and can no longer be undone. This tool uses a single marginal rate for a clean estimate; consult a tax professional for a bracket-by-bracket and IRMAA projection.

Tips, Tricks & Pitfalls to Watch

  • Convert in low-income years — gap years, early retirement before Social Security, or years with large deductions let you convert at a lower bracket.
  • Use partial conversions to fill a bracket — convert only enough to reach the top of your current bracket, not spill into the next.
  • Pay the tax from outside funds so the entire balance compounds tax-free in the Roth — and avoid the 10% penalty if you are under 59½.
  • Mind the conversion 5-year rule — converted principal withdrawn within five years (under 59½) can incur a 10% penalty.
  • Reduce future RMDs — converting now shrinks the Traditional balance that would force larger taxable withdrawals starting at age 73.
  • Watch the IRMAA cliff — if you are near 63+, keep each year's conversion below the next Medicare premium threshold.
  • Beware the pro-rata rule for backdoor Roths — roll pre-tax IRA balances into a 401(k) first to keep the conversion nearly tax-free.

Roth Conversion Math (2025)

How converting now compares to leaving the money in a Traditional account — and the worked example behind the result.

Tax Now = Conversion Amount × Current Tax Rate

Example:

$100,000 converted at a 22% marginal rate

100000 × 0.22
= $22,000 tax due this year

Variables:

Conversion Amount - Pre-tax dollars moved into the Roth
Current Tax Rate - Your marginal rate this year

Roth Future = Roth Principal × (1 + r)^n

Example:

$78,000 at 7% for 20 years, never taxed again

78000 × (1.07)^20
= ≈ $301,800 (tax-free)

Variables:

Roth Principal - Amount − tax (when paid from the conversion)
r - Annual return
n - Years of growth

Trad After-Tax = Amount × (1 + r)^n × (1 − Retirement Tax Rate)

Example:

$100,000 at 7% for 20 years, taxed at 24% on withdrawal

100000 × (1.07)^20 × (1 − 0.24) = 386,968 × 0.76
= ≈ $294,096 (after tax). Net benefit of converting ≈ +$7,700

Variables:

Amount - Full pre-tax balance left in place
Retirement Tax Rate - Marginal rate on future withdrawals

These formulas provide the mathematical foundation for the calculations. Actual results may vary based on rounding, compounding frequency, and specific lender policies.

How We Calculate & Keep This Accurate

We compare two scenarios over your chosen horizon. Convert: the conversion is taxed at your current marginal rate; the remaining principal (or the full amount, if you pay tax from outside funds) grows tax-free as FV = principal × (1 + return)^years. Don't convert: the full pre-tax amount grows as FV = amount × (1 + return)^years, then is reduced by your expected retirement tax rate. The net benefit is the tax-free Roth value minus the after-tax Traditional value.

We use a single flat marginal rate for both the conversion and retirement withdrawals, so the estimate does not model bracket-by-bracket effects, the pro-rata rule, Medicare IRMAA surcharges, state taxes, or the opportunity cost of outside funds used to pay the tax. Results are planning estimates and may differ from a tax professional's projection for 2025.

Data & Freshness

Figures reflect 2025 tax-year data.

Last updated June 9, 2026 · Maintained by the Financial Calculator editorial team.

Roth Conversion Calculator — Frequently Asked Questions

Answers to the most common questions about conversion tax, the pro-rata rule, IRMAA, the 5-year rule, and partial conversions.

What is a Roth conversion?

A Roth conversion is the act of moving money from a pre-tax retirement account — such as a Traditional IRA, a SEP/SIMPLE IRA, or a 401(k) — into a Roth IRA. Because Traditional accounts hold dollars that have never been taxed, the converted amount is added to your taxable income in the year of the conversion and taxed at your ordinary income tax rate. In exchange, the money then grows entirely tax-free inside the Roth, and qualified withdrawals in retirement are never taxed again. There is no income limit on conversions (unlike direct Roth contributions), which is why high earners use them, including through the 'backdoor Roth' strategy. A conversion is permanent — since 2018 the IRS no longer allows you to 'recharacterize' or undo it, so the decision should be made deliberately. The core trade-off is paying tax now at your current rate versus paying tax later at your retirement rate. If you expect to be in the same or a higher tax bracket in retirement, paying tax now can leave you better off. This calculator models that trade-off across the years you let the money grow.

When does a Roth conversion make sense?

A Roth conversion tends to make sense when you can pay the conversion tax at a rate that is equal to or lower than the rate you expect to pay when you eventually withdraw the money. The clearest wins come during low-income years: early retirement before Social Security and Required Minimum Distributions (RMDs) begin, a gap year between jobs, a sabbatical, or a year with large business losses or deductions. In those years your marginal bracket may temporarily drop, letting you convert at 10–12% instead of 22–24%. Conversions also make sense if you expect tax rates to rise in the future, if you want to leave tax-free money to heirs (Roth accounts have no RMDs during your lifetime), or if you have funds outside the retirement account to pay the tax bill so the entire balance keeps compounding tax-free. Conversely, if converting would push you into a much higher bracket this year, trigger Medicare IRMAA surcharges, or you will need the money soon, the math often favors waiting. Use partial conversions to convert only enough to 'fill up' your current bracket without spilling into the next one.

How much tax will I owe on a conversion?

The tax on a Roth conversion is calculated by adding the converted amount to your other taxable income for the year and applying your ordinary income tax rates — the same brackets that apply to wages. There is no special lower rate as there is for long-term capital gains. For a rough estimate, multiply the conversion amount by your marginal tax rate: converting $100,000 at a 22% marginal rate costs roughly $22,000. The reality is often more nuanced because a large conversion can push part of the converted amount into a higher bracket. For example, if the conversion fills the rest of your 22% bracket and then spills into the 24% bracket, the top slice is taxed at 24%. The conversion can also have ripple effects: it can increase the taxable portion of your Social Security, raise your Medicare Part B and D premiums two years later through IRMAA, and affect income-based credits and deductions. You generally owe the tax for the year of the conversion, and you may need to make estimated tax payments to avoid an underpayment penalty. This calculator uses a single marginal rate for a clean estimate; consult a tax professional for a bracket-by-bracket projection.

Should I pay the conversion tax from the IRA or from outside?

Paying the conversion tax from outside (taxable) funds is almost always the better choice, and this calculator lets you compare both. When you pay the tax from outside money, the entire converted balance lands inside the Roth and compounds tax-free for decades — every dollar of the original pre-tax balance keeps working for you. When you instead withhold the tax from the conversion itself, less money makes it into the Roth: converting $100,000 at a 22% rate leaves only $78,000 growing tax-free. Over 20 years at 7%, that missing $22,000 of principal would have grown to tens of thousands of dollars. There is a second penalty for paying tax from the IRA if you are under 59½: the withheld amount is treated as a taxable distribution and can trigger an additional 10% early-withdrawal penalty. The only situations where paying from the account makes sense are when you simply have no outside cash, or when the outside funds are earmarked for something with an even higher return. As a rule of thumb, if you cannot afford the conversion tax from outside savings, the conversion may be larger than you should be doing this year — consider a smaller partial conversion instead.

What is the pro-rata rule?

The pro-rata rule determines how much of a conversion is taxable when you hold both pre-tax (deductible) and after-tax (non-deductible) money across all of your Traditional, SEP, and SIMPLE IRAs. The IRS does not let you convert only the after-tax portion to dodge taxes; instead it treats all of your IRA balances as one combined pot and taxes the conversion in proportion to the pre-tax share. For example, if you have $93,000 of pre-tax money and $7,000 of after-tax basis across your IRAs — a total of $100,000 — then 93% of any conversion is taxable, regardless of which dollars you intend to move. This rule frequently surprises people attempting a 'backdoor Roth,' where they make a $7,000 non-deductible Traditional contribution intending to convert it tax-free, only to discover that a large existing pre-tax IRA makes most of the conversion taxable. The aggregation applies only to IRAs you own (not your spouse's, and not 401(k)s). A common workaround is to 'roll in' your pre-tax IRA balances to an employer 401(k) first, leaving only after-tax basis in IRAs, so the backdoor conversion becomes nearly tax-free. The taxable fraction is reported on IRS Form 8606.

Can a conversion raise my Medicare premiums (IRMAA)?

Yes. A Roth conversion increases your Modified Adjusted Gross Income (MAGI), and Medicare uses MAGI to determine your Income-Related Monthly Adjustment Amount (IRMAA) — surcharges added to your Part B and Part D premiums. The catch is the two-year lookback: Medicare sets this year's premiums based on the MAGI you reported two years earlier. So a large conversion at age 63 can spike your premiums at age 65, and a conversion at 65 can raise premiums at 67. IRMAA is a 'cliff' system, meaning that going even one dollar over a threshold bumps you into the next surcharge tier for the whole year — potentially adding hundreds of dollars a month per person. If you are near or over 63, model the IRMAA impact carefully before converting, and consider keeping each year's conversion below the next IRMAA threshold. The good news is the surcharge is temporary (it applies to a single year's income), and the long-term benefit is that Roth withdrawals later do not count toward MAGI at all, which can keep your future IRMAA and taxable Social Security lower. This calculator does not model IRMAA tiers directly, so factor it in separately if you are approaching Medicare age.

What is the 5-year rule for conversions?

Roth conversions carry their own five-year clock that is separate from the five-year rule for Roth contributions, and confusing the two causes costly mistakes. Each conversion you make has its own five-year holding period that begins on January 1 of the year of that conversion. If you withdraw the converted principal before that five-year period is up and you are under age 59½, you can owe a 10% penalty on the amount — the very penalty the conversion was supposed to avoid — even though you already paid income tax at conversion. Once you reach age 59½, this conversion five-year rule no longer applies to the principal, so penalties are not a concern. There is also a broader five-year rule governing whether earnings come out tax-free: your Roth must have been open for at least five years (counting from your first-ever Roth contribution or conversion) and you must be 59½ for earnings to be fully qualified. The practical takeaway is that conversions are best suited to money you will not need for at least five years, ideally as long-term retirement savings. If you are doing a series of annual conversions ('a Roth conversion ladder' for early retirement), plan each year's conversion to season for five years before you tap it.

Should I do partial conversions?

Partial conversions — converting a portion of your Traditional balance each year rather than all of it at once — are usually the smartest approach, and they are the heart of good conversion planning. The main reason is bracket management: by converting only enough to 'fill up' your current tax bracket without spilling into the next one, you cap the rate you pay on the converted dollars. For instance, if you are single and your taxable income leaves $40,000 of room before the 24% bracket begins, converting roughly $40,000 keeps the whole conversion taxed at 22% or less. Spreading conversions over several years also smooths your income, helps you stay under Medicare IRMAA thresholds, limits how much of your Social Security becomes taxable, and lets you respond to changing tax laws and market conditions. A popular strategy is the 'Roth conversion ladder,' where an early retiree converts a set amount annually during low-income years between leaving work and claiming Social Security, draining the Traditional account gradually before RMDs would force larger taxable withdrawals at 73. The trade-off is that partial conversions take discipline and years to complete, and you keep paying tax annually. But for most people, several modest conversions beat one large conversion that needlessly pushes income into a higher bracket. Re-run this calculator each year with your actual numbers to size that year's conversion.
US Roth Conversion Calculator User Reviews

Disclaimer: Results are estimates for planning only and do not constitute tax, legal, lending, or investment advice. Actual paycheck and tax outcomes can vary based on employer settings, local rules, and personal elections. Consult a qualified US tax professional, CFP, or attorney before making financial decisions.