Roth Conversion Calculator

This Roth conversion calculator estimates the federal tax cost of converting traditional IRA or 401(k) funds to Roth this year, using your real marginal tax bracket — then compares the long-term after-tax value of converting versus leaving the money traditional.

Worked example (the defaults): converting $50,000 on top of $80,000 of existing taxable income, filing single, under 2026 tax brackets. That conversion costs $11,486 in federal tax — an effective rate of 22.97% on the converted amount, since it's taxed at your marginal rate but blended across whichever brackets it pushes you through. The conversion pushes your top marginal rate to 24%. Grown at 7% annually for 20 years, the converted Roth balance reaches $149,037 tax-free, versus $147,048 if the same $50,000 had stayed traditional and been taxed at withdrawal at today's marginal rate.

That comparison is close in this example precisely because the conversion pushed the person into a materially higher bracket — the math favors conversion more clearly when you convert in a lower-income year. Already required to take distributions? RMDs can't be converted to Roth — check the RMD Calculator first for what's mandatory before deciding what additional amount to convert voluntarily.

A Roth conversion adds the converted amount to your ordinary taxable income for the year, per IRS guidance on Roth IRAs. The tax cost isn't a flat rate — it's the difference between two full bracket calculations:

This matters because a conversion can straddle multiple brackets — the first dollars converted might be taxed at your current marginal rate, while later dollars in a large conversion push into the next bracket up. The "effective rate on conversion" this calculator shows is the blended rate across whatever brackets the conversion actually spans, which is usually different from — and can be higher than — your marginal rate before converting.

Roth conversions generally work best in years when your taxable income is unusually low — early retirement before Social Security and RMDs begin, a career gap, or a low-income year for any reason. Converting in a low bracket now, to avoid a higher bracket later (from RMDs, for instance), is the core strategic logic. Converting in a high-income year, as in the default example above, still grows tax-free forever, but the upfront tax cost eats into the advantage.

Two things this calculator doesn't model: state income tax (which applies to the conversion in most states) and Medicare IRMAA surcharges, which can be triggered by a large conversion pushing your income above certain thresholds two years later. Both are worth checking with a tax professional before converting a large amount in a single year — spreading a big conversion across multiple years (a "conversion ladder") is a common way to manage both issues.

This Roth conversion calculator uses your actual 2026 federal tax bracket to show exactly what converting a traditional IRA or 401(k) balance to Roth costs this year — not a rough percentage, but the real marginal-bracket arithmetic on your specific income. Enter the amount you want to convert, your current taxable income before conversion, your filing status, and how many years you expect the money to grow. The calculator returns the exact tax cost, the effective rate on the conversion, and a long-term comparison of Roth vs. staying traditional.

The tax cost of a Roth conversion depends entirely on which brackets the converted amount pushes you through. Conversion income is treated as ordinary income in the year you convert — it stacks on top of your other taxable income. If your taxable income is $80,000 (single) and you convert $50,000, the first $3,350 of the conversion fills the rest of the 22% bracket, and the remaining $46,650 is taxed at 24%. Total conversion tax: $11,533 at an effective rate of 23.1%.

The break-even math is what most calculators get wrong. Our tool uses your current marginal rate as an estimate for the future withdrawal tax rate on the traditional balance — a conservative assumption. If you expect to be in a higher bracket in retirement (larger RMDs, Social Security, other income), conversion is even more advantageous than the calculator shows. If you'll be in a lower bracket, traditional may win.

The best case for Roth conversion: a low-income year when your taxable income is depressed — early retirement before Social Security starts, a year between jobs, or before RMDs force large distributions. Converting $30,000 at $40,000 income costs only $5,752 at an effective rate of 19.2%, and that money grows tax-free for decades. For an IRA to Roth conversion calculator that models your specific numbers across multiple years, use the tool above with different conversion amounts to find your optimal annual bracket-filling amount.

Related tools: RMD Calculator (understand what traditional distributions will look like at 73+), Roth vs Traditional IRA Calculator (pre-contribution decision), and our Safe Withdrawal Rate guide for the broader drawdown picture.

A single large conversion can push you into a significantly higher tax bracket and trigger Medicare IRMAA surcharges two years later. Most tax-efficient Roth conversion plans spread smaller amounts across multiple years — a strategy called a conversion ladder.

The target: fill your current tax bracket without crossing into the next one. In 2026, the 22% bracket for single filers extends from $47,150 to $100,525 of taxable income, and the 24% bracket from $100,525 to $191,950. A retiree with $60,000 in other income (Social Security, pension, dividends) has roughly $40,000 of 22% headroom for a Roth conversion before hitting 24%. Converting $40,000 per year for several years is almost always more tax-efficient than converting $200,000 in a single year.

Per IRS Publication 590-A, there is no income limit on Roth conversions (income limits only apply to direct Roth IRA contributions). You can convert any amount at any age, as long as you pay the ordinary income tax on the amount converted. The 72(t) SEPP Calculator models the parallel strategy for accessing IRA funds before 59½ without converting.

This estimates federal income tax only. It does not include state income tax on the conversion, the higher Medicare premiums (IRMAA) a large conversion can trigger two years later, or the pro-rata rule: if any of your traditional IRA money is after-tax (nondeductible) basis, only part of a conversion is taxable, and the calculator treats all of it as taxable.