Roth Conversion Calculator: Tax Cost by Bracket

Use this calculator to see what a Roth conversion would cost you in tax this year and whether it is likely to leave you better off by retirement. Enter your age, traditional and Roth balances, the amount you want to convert each year, your filing status and income, the federal rate you expect in retirement, and your state tax rate. The tool prices the conversion with the 2026 brackets, shows how much room is left in your bracket, projects both balances to retirement, and estimates your first required minimum distribution (RMD).

Short answer: a Roth conversion is taxed as ordinary income in the year you convert, so its cost is the extra tax it adds on top of your other income, not your top bracket rate times the amount. Converting pays off when the rate you pay now is lower than the rate you would otherwise pay when the money comes out of the traditional IRA. Because the One Big Beautiful Bill Act made the current brackets permanent (Rev. Proc. 2025-32, section 3.01), there is no 2025 or 2026 deadline driving that comparison.

This calculator is for informational purposes only. Results are estimates built on the assumptions you enter, such as a constant return and constant income, and real outcomes will differ.

For a deeper look at multi-year planning, read Roth conversion tax strategies and the Roth conversion ladder guide.

For new contributions rather than conversions, the Roth IRA calculator checks the 2026 income limits and projects tax-free growth.

How much tax will a Roth conversion add?

The calculator works out your regular taxable income (income minus the standard deduction of $16,100 single, $32,200 married filing jointly or $24,150 head of household for 2026), then computes federal tax twice: once without the conversion and once with it. The difference is the conversion's federal cost. Your state rate is applied to the converted amount on top.

2026 federal brackets for married couples filing jointly

Single filers hit the 22% bracket above $50,400 of taxable income and the 24% bracket above $105,700, per Rev. Proc. 2025-32. The "gross income" column assumes the standard deduction and no other deductions.

Worked example: $50,000 conversion on $100,000 of income

A married couple with $100,000 of income converts $50,000 and pays 5% state tax.

1. Taxable income before converting: $100,000 − $32,200 = $67,800.
2. After converting: $117,800.
3. The first $33,000 of the conversion fills the rest of the 12% bracket (to $100,800): $33,000 × 12% = $3,960.
4. The remaining $17,000 lands in the 22% bracket: $17,000 × 22% = $3,740.
5. Federal cost: $7,700. State cost: $50,000 × 5% = $2,500. Total: $10,200, an effective 20.4%.

Pricing the whole conversion at the 22% marginal rate would have overstated the federal cost by $3,300. Those first $33,000 are the cheapest dollars this couple can convert.

Does converting actually leave you better off?

The calculator compares two versions of your future with the same money in each:

• No conversion: the traditional IRA grows, and the cash you would have spent on conversion tax stays invested at the same return.
• Conversion: you convert the amount you entered every year until retirement, pay the tax from that outside cash, and the Roth grows tax-free.

At retirement it values the traditional balance after tax at your expected federal rate plus your state rate. The net benefit is after-tax wealth with conversions minus after-tax wealth without them. Under these assumptions each converted dollar is worth its growth multiplied by the difference between your retirement rate and the rate you paid to convert. If both rates are equal, converting is a wash.

The default projection

With a $500,000 traditional IRA at age 55, $50,000 converted every year until 65, a 7% return, and an expected 22% federal plus 5% state rate in retirement (27% in total):

Now look at what happens if the couple converts only $33,000 a year, just enough to fill the 12% bracket. The net benefit is the same $48,786. The extra $17,000 a year in the default plan is taxed at 22% + 5% = 27%, exactly the rate it would face in retirement, so it adds nothing. Converting the full $143,600 needed to fill the 22% bracket each year empties the IRA in about four years and cuts the net benefit to roughly $23,500, because fewer dollars get converted at 12%.

If the same couple expects to be in the 12% bracket in retirement, the default plan loses about $25,100 compared with not converting. The retirement rate you enter drives the answer, which is why the calculator also shows the bracket your stated retirement income need would fall in at today's brackets.

How much should you convert each year?

The conversion strategy setting turns the bracket table into a target:

• Conservative: convert up to the top of your current bracket. For the example couple that is $33,000.
• Moderate: convert up to the top of the next bracket. For the couple, $143,600 fills the 22% bracket.
• Aggressive or custom: use the amount you enter.

A sound rule is to stop converting once the next dollar would be taxed at a higher rate than you expect on withdrawals. The years between retirement and the start of Social Security or RMDs are often the cheapest conversion window, because wages have stopped and taxable income is low.

To see a whole conversion plan with your own numbers, the Retirement Withdrawal Planner spreadsheet runs every year of retirement next to a no-conversion plan: which years to convert, how much, and what it does to your RMDs, Medicare premiums and lifetime tax.

How RMDs change the picture

Traditional IRAs and 401(k)s require minimum distributions starting at age 73 if you were born from 1951 through 1959, or age 75 if you were born in 1960 or later (IRS RMD FAQs). The first RMD is your prior year-end balance divided by the factor in the Uniform Lifetime Table in Publication 590-B: 26.5 at 73 and 24.6 at 75. Once RMDs have started, the RMD calculator works out each year's amount and projects the ones ahead.

The calculator takes your birth year from your age, grows both traditional balances from retirement to the year before RMDs begin, and divides by the factor. In the default case (born 1971, RMDs at 75):

• Without conversions: $1,934,842 ÷ 24.6 = a first RMD of $78,652.
• With conversions: $480,763 ÷ 24.6 = $19,543.

At a 27% combined rate that is about $15,960 less tax in the first RMD year alone, and later RMDs shrink in proportion. Once RMDs start, the year's RMD must come out before you convert, and the RMD itself cannot be converted. Roth IRAs, and since 2024 Roth 401(k) accounts, have no lifetime RMDs.

Costs that do not show up in the bracket math

A conversion raises your adjusted gross income, which can trigger other costs the calculator does not include:

• Medicare premiums: the income-related surcharges on Part B and Part D premiums are based on your modified AGI from two years earlier, so a conversion at 63 can raise premiums at 65.
• Taxable Social Security: extra income can make more of your benefits taxable; the taxable Social Security calculator shows by how much.
• Net investment income tax: a conversion is not investment income, but it raises MAGI, which can push your dividends and gains over the 3.8% NIIT threshold. See the NIIT calculator.
• Credits and deductions with income limits, such as the senior deduction or premium tax credits. If you buy marketplace coverage before 65, a conversion that pushes household income over 400% of the poverty line ends the credit for the year; check with the ACA premium tax credit calculator.

Rules to know before converting

• Paying the tax: pay it from savings outside the IRA. Withholding from the conversion shrinks the Roth, and before age 59½ the withheld amount can be hit by the 10% additional tax.
• Five-year clock: each conversion has its own five-year period before the converted amount can come out penalty-free if you are under 59½ (Publication 590-B).
• No undo: conversions cannot be recharacterized back to a traditional IRA, so convert once your income for the year is predictable.
• Pro-rata rule: if you have after-tax (nondeductible) money in any traditional IRA, each conversion is partly taxable and partly tax-free. The backdoor Roth calculator handles that case.
• Estimated tax: a large conversion can create an underpayment penalty unless you raise withholding or make an estimated payment.

Roth conversions and heirs

Most non-spouse beneficiaries must empty an inherited IRA within 10 years. Withdrawals from an inherited traditional IRA are taxed at the heir's rate, often during their peak earning years, while qualified withdrawals from an inherited Roth are tax-free. If your children will be in a higher bracket than you are now, converting shifts the tax to the lower rate. Paying the conversion tax also shrinks your taxable estate, although only estates above the $15 million federal exemption owe estate tax.

Limits of this projection

The projection keeps your income, the 2026 brackets and the standard deduction constant in real terms, uses one return for every account, and applies a single flat retirement rate to all traditional withdrawals. It does not model itemized deductions, capital gains on the taxable account that pays the conversion tax, or the pro-rata rule. Use it to compare conversion sizes against each other, then check a specific year's conversion with the federal tax bracket calculator or the IRA withdrawal tax calculator. A conversion is not a fix for an excess Roth IRA contribution; use the excess Roth IRA contribution calculator for that.