Roth Conversion Calculator

The short answer

• The amount you convert is taxed as ordinary income in the year you convert.
• Converting pays off when your tax rate later would be higher than the rate you pay now.
• A married couple with $60,000 of other income can convert about $73,000 in 2026 and stay in the 12% bracket.
• Pay the tax from other savings if you can, and watch the Medicare surcharge thresholds from age 63.

What a Roth conversion is

Traditional IRAs and 401(k)s hold pre-tax money: you got a deduction going in, and you pay income tax coming out. A Roth IRA is the reverse. A conversion switches money from the first to the second by paying the deferred tax now. Since 2010 there is no income limit, and you can convert any amount, all at once or a slice each year.

After the conversion, the money grows tax-free, comes out tax-free in retirement once the rules are met, and has no required minimum distributions during your life.

How a conversion is taxed

The converted amount is added to your other income for the year. It isn’t taxed at a flat rate: it fills your brackets from where your other income leaves off. The calculator runs the 2026 federal return with and without the conversion and reports the difference.

That is 12% of the conversion. The 10% penalty for early withdrawals doesn’t apply to the conversion itself, whatever your age, as long as the money goes straight into the Roth.

Filling your bracket

The most common approach is to convert just enough to reach the top of your current bracket. In 2026 the 12% bracket for married couples ends at $100,800 of taxable income, or $133,000 of income after the $32,200 standard deduction.

Converting $73,000 in the first example costs $8,760, exactly 12%. Repeating that every year until RMDs start can move a large traditional balance into a Roth at a low rate. Our tax bracket calculator shows all seven brackets.

What a big conversion costs

Converting a lot in one year pushes part of it into higher brackets:

On $200,000 the tax is $37,028, an average of 18.5%, with the top slice taxed at 24%. Spreading the same amount over three years at the top of the 12% bracket would cost noticeably less, and a $260,000 AGI also triggers Medicare surcharges two years later.

When converting pays off

The calculator compares two paths for the same money. Convert: the whole amount grows in the Roth and comes out tax-free. Don’t convert: it grows in the traditional IRA and is taxed at your future rate, while the money you would have used for the tax stays invested in a taxable account.

Even at the same 12% rate later, converting edges ahead, because paying the tax from outside savings effectively moves more money into the tax-free account. The bigger the jump in your future rate, the bigger the gain.

The break-even tax rate

The break-even rate is the future tax rate at which both paths leave you the same. If you pay the tax from the converted amount, it is simply your average rate on the conversion: 12% in the example. Paying from outside savings lowers it, here to about 11.1%, because those savings would have faced tax on their growth.

Paying the tax: outside money or the IRA

Paying from the IRA, a conversion at 12% only breaks even if your future rate is above 12%; at exactly 12% the two paths tie at $105,449.

State income tax

Most states tax a conversion like any other income. In California, the same $50,000 conversion adds about $2,235 of state tax, taking the total to $8,235, or 16.5%. The calculator treats the conversion like wages; some states exempt part of retirement income for older residents, so check your own state. A planned move matters too: converting after moving from a high-tax state to a no-tax state, such as Florida or Texas, can save the state tax entirely.

The best years to convert

1. Low-income yearsBetween jobs, a sabbatical, or a business loss

   Your brackets are mostly empty.

2. Retirement to 70Before Social Security and RMDs

   Often the lowest-tax years of adult life.

3. Market dipsConvert when values are down

   The same number of shares costs less tax; the recovery happens in the Roth.

4. Before RMD age73, or 75 if born in 1960 or later

   Once RMDs start, they must come out first and fill your low brackets.

Our RMD calculator shows the withdrawals you’ll be forced to take later, which is often what makes converting now worthwhile.

Converting after 65

From 65 your standard deduction is larger and, from 2025 to 2028, you also get the senior deduction of $6,000 each. A married couple both 65+ with $60,000 of other income pays only $5,754 to convert $50,000, an average of 11.5%, because part of the conversion fills the 10% bracket. The senior deduction phases out above $150,000 of modified AGI for couples, so very large conversions can lose it.

Medicare surcharges (IRMAA)

Medicare Part B and Part D premiums rise in steps for higher incomes, using your modified AGI from two years earlier. In 2026 the standard Part B premium is $202.90 a month, and surcharges start above $109,000 of modified AGI for single filers and $218,000 for married couples filing jointly.

Because of the two-year look-back, conversions from age 63 onward can raise premiums. Each tier is a cliff: one dollar over adds the whole surcharge, so it is worth sizing a conversion to stay just under a line.

Social Security and the tax torpedo

Once you claim Social Security, extra income can make up to 85% of your benefits taxable, so each converted dollar can drag more benefits into tax. The effective rate on a conversion can then be well above your bracket. Converting before you claim avoids this. Our Social Security calculator shows how much of your benefit is taxed at your income.

The five-year rules

• Each conversion starts its own five-year clock on January 1 of the year you convert. Take out converted money within five years and before 59½, and the 10% penalty applies (no income tax, since it was taxed already).
• Earnings are tax-free only once you are 59½ and five years have passed since your first Roth contribution or conversion.
• Withdrawals come out in order: contributions first, then conversions oldest first, then earnings.

The pro-rata rule

If any of your traditional, SEP or SIMPLE IRAs hold after-tax money, each conversion is a mix of pre-tax and after-tax dollars in proportion to your total IRA balances on December 31. You can’t pick only the after-tax part. Money in a 401(k) doesn’t count, which is why people sometimes roll pre-tax IRA money into a workplace plan first. Report every conversion on Form 8606.

Conversions and your heirs

Most heirs other than a spouse must empty an inherited IRA within 10 years. A large traditional IRA can land on top of their peak earning years and be taxed at high rates. An inherited Roth has the same 10-year rule, but withdrawals are tax-free. If your heirs are likely to pay more tax than you, converting can be a gift to them.

How to convert

1. Open a Roth IRA at the same provider as your traditional IRA, if you don’t have one.
2. Ask for a conversion of a dollar amount or specific shares; it is usually an online form.
3. Choose no tax withholding if you will pay from other savings, then cover the tax with estimated payments or extra paycheck withholding.
4. Keep the Form 1099-R you receive and file Form 8606 with your return.

A large conversion can mean an underpayment penalty if you don’t pay enough tax during the year. Making an estimated payment in the quarter you convert avoids it.

Common mistakes

• Converting so much that part of it jumps into a higher bracket for no reason.
• Forgetting the Medicare look-back from age 63.
• Paying the tax from the IRA when under 59½.
• Ignoring other IRA balances under the pro-rata rule.
• Converting an RMD, which isn’t allowed.
• Expecting to undo it; recharacterizations ended in 2018.

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