Free Roth conversion calculator. See your 2026 tax cost, break-even age, and lifetime savings before converting your traditional IRA to Roth.
By Ziv Shay — Last updated May 29, 2026
A Roth conversion makes sense when the tax rate you pay today is lower than the rate you (or your heirs) would pay later — and a Roth conversion calculator answers that by comparing your upfront tax bill against decades of tax-free growth. For most people the break-even point lands 8–15 years out: convert at 22% today, let the money compound tax-free, and you come out ahead as long as you don't need that cash before the break-even year and you pay the tax from a separate account. Below is exactly how the math works, a full $100,000 worked example, and the three traps that quietly wreck otherwise-good conversions.
A Roth conversion moves money from a pre-tax account — a traditional IRA, SEP-IRA, or rolled-over 401(k) — into a Roth IRA. The converted amount is added to your ordinary income for the year and taxed at your marginal rate. In exchange, every future dollar of growth and every qualified withdrawal comes out 100% tax-free, and the Roth has no required minimum distributions (RMDs) during your lifetime.
You are essentially making a bet: my tax rate now is lower than my tax rate (or my beneficiaries' tax rate) will be when this money comes out. A calculator's job is to price that bet in real dollars instead of gut feel.
Because a conversion is taxed as ordinary income, the conversion amount stacks on top of your existing income. Here are the 2026 federal brackets for a single filer (the standard deduction is $15,000 single / $30,000 married filing jointly):
| Rate | Single taxable income |
|---|---|
| 10% | $0 – $11,925 |
| 12% | $11,926 – $48,475 |
| 22% | $48,476 – $103,350 |
| 24% | $103,351 – $197,300 |
| 32% | $197,301 – $250,525 |
| 35% | $250,526 – $626,350 |
| 37% | $626,351+ |
The key insight: a conversion can push part of your income into a higher bracket. If you're single with $90,000 of taxable income and convert $40,000, the first $13,350 of that conversion is taxed at 22% but the remaining $26,650 jumps to 24%. Good calculators show this blended (effective) rate on the conversion, not just your top marginal rate.
Every reliable calculator needs five inputs:
The output you care about is the break-even year: the point at which the tax-free Roth balance overtakes a traditional account that kept the money invested but owes tax on the back end.
Maria is 60, single, with $70,000 of taxable income. She converts $100,000 from her traditional IRA.
At a 6% return, Scenario A's $100,000 becomes about $179,000 in 10 years — all tax-free. Had she left $100,000 in the traditional IRA, it would also grow to ~$179,000, but withdrawing it later at even a 22% rate costs ~$39,000 in tax. The conversion's break-even versus that future tax bill arrives around year 7–8, after which every additional year is pure tax-free upside. Paying the tax from outside money (Scenario A) is what makes the break-even arrive that early.
Break-even is driven by three levers:
If you hold any pre-tax money across all your traditional, SEP, and SIMPLE IRAs, the IRS won't let you convert only your after-tax (nondeductible) contributions. Conversions are taxed proportionally. Example: you have $90,000 pre-tax and $10,000 after-tax across your IRAs. Convert $10,000 and only 10% is tax-free — the other $9,000 is taxable. This is the most common surprise for "backdoor Roth" filers.
Each conversion starts its own five-year clock. Withdraw converted principal before five years have passed (and before age 59½) and you can owe a 10% penalty — even though you already paid income tax on it. Plan conversions you might tap soon with this clock in mind.
A large conversion inflates your Modified Adjusted Gross Income (MAGI), which can trigger IRMAA Medicare surcharges two years later (a single $1 over a threshold can add ~$70–$420/month to Part B + D premiums) and can spike ACA marketplace premiums. The fix is "bracket-filling" — converting smaller amounts over several years to stay under the cliffs rather than one giant conversion.
Strong candidates:
Usually skip it when: you'll need the money within five years, you expect a lower tax bracket in retirement, you'd have to pay the conversion tax from the IRA itself, or the conversion shoves you into IRMAA territory with no offsetting benefit.
Bracket-filling: convert just enough to "top off" your current bracket — e.g., if you're $20,000 below the top of the 12% bracket, convert ~$20,000 at 12% and stop. Partial multi-year conversions spread a large IRA across 5–10 years to avoid bracket creep and IRMAA. Down-market conversions let you move more shares for the same tax bill. For the cash you set aside to pay the tax, a short-term vehicle like a CD ladder keeps it liquid and earning. And don't overlook your HSA's triple tax advantage as a complementary tax-free bucket alongside your new Roth.
The converted amount is taxed as ordinary income at your marginal rate(s) for the year. Because it stacks on top of your existing income, part of a large conversion can land in a higher bracket — so your effective rate is usually a blend. A $50,000 conversion for someone already in the 22% bracket with room to spare costs about $11,000; if it spills into the 24% bracket, the spillover portion costs more.
It's the year when your tax-free Roth balance surpasses what a traditional account would net after future taxes. With outside funds paying the tax and a 6–7% return, break-even typically falls between years 7 and 15. The lower your conversion-year tax rate relative to your expected retirement rate, the sooner you break even.
Almost always from outside savings. Paying from the IRA shrinks the amount that grows tax-free and, if you're under 59½, the withheld portion can trigger a 10% early-withdrawal penalty. Using outside cash is what makes conversions pay off years earlier.
If you hold any pre-tax money in any traditional, SEP, or SIMPLE IRA, the IRS taxes conversions proportionally across pre-tax and after-tax balances — you can't cherry-pick only the after-tax dollars. It matters most for backdoor Roth contributions. Rolling pre-tax IRA money into an employer 401(k) first can clear the way.
No. Unlike Roth contributions, conversions have no dollar limit and no income limit — you can convert any amount in any year. The practical limits are the tax bill you're willing to absorb and staying below IRMAA and ACA-subsidy cliffs.
This content is for educational purposes only and does not constitute financial advice. Consult a qualified financial advisor.
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