Roth conversion calculator

What is a Roth conversion?

A Roth conversion moves money out of a traditional IRA, SEP IRA, SIMPLE IRA, or 401(k) and into a Roth IRA. The pre-tax portion joins your ordinary income for that year, and in exchange the money grows and comes out tax-free later.⁵

How does a Roth conversion work?

You tell the custodian how much to move, the account type changes, and the taxable amount lands on Form 8606 and your Form 1040. There is no dollar cap and no restriction on how often you do it.

Roth conversion tax at four conversion amounts

The table shows the 2026 federal tax on four conversion amounts for a single filer with $60,000 of other income and a joint return with $120,000.

Assumes zero basis, filers under 65 so no age-based deductions apply, and no state tax.

The effective rate stays below the top bracket the conversion reaches because the first dollars fill lower brackets. Run your own income and amount through the Roth conversion calculator above to see your figure.

2026 tax brackets and deductions that set your rate

Conversion income fills whatever room is left in your current bracket before spilling into the next one.¹

There are two age-based deductions for people 65 and older, and they stack. Missing the second one is a common way to overstate a retiree's tax bill.¹

The senior bonus deduction runs for tax years 2025 through 2028 only, is not indexed, and requires married filers to file jointly. It phases out at 6% of MAGI above the threshold.²

That 6%reduction applies to each person's $6,000 allowance, not to a couple's combined $12,000. On the Schedule 1-A worksheet, line 34 takes 6% of the excess and line 35 subtracts it from $6,000, and only then do the two spouses' amounts get added together.² The deduction therefore reaches zero at $100,000 of excess MAGI in every case.

So a joint return is fully phased out at $250,000 whether one spouse is 65 or both are. A large conversion can push you through this range, which adds an effective 6% on top of your bracket while it lasts.

When the tax on a Roth conversion is due

The tax on a Roth conversion is due for the calendar year you convert, because the conversion counts as income for that year and belongs on that year's return.⁵ You can pay it during the year through more withholding from wages or another payment source, or through estimated tax payments. So raise your withholding or schedule an estimated payment in the quarter you convert, or you may owe an underpayment penalty.

Step 3 of how to use the calculator explains why withholding the tax from the conversion itself costs more.

Converting a traditional 401(k) to a Roth 401(k)

Converting a traditional 401(k) to a Roth 401(k) moves pre-tax money into the plan's designated Roth account, and the pre-tax amount you convert is taxable that year. Your IRAs do not enter this calculation, because the plan tracks its own after-tax basis and does not aggregate with your IRAs.

To price an in-plan conversion in the Roth conversion calculator, enter the amount to convert, the pre-tax amount as the balance, and zero basis if you are converting only pre-tax money. The bracket stacking, IRMAA, and break-even outputs work the same way. Each plan decides whether to allow in-plan Roth conversions, so check your plan's rules before you count on one.

Paying the tax from cash vs from the conversion

When the tax comes out of the IRA itself, you shrink the sheltered balance, and the break-even lands close to your current bracket. Pay from a taxable brokerage account and something different happens: you have moved money that was paying tax on its dividends and gains every year into an account that never will.

The size of that swing can be large, and it moves with the growth and horizon assumptions behind it. No government source publishes break-even rates, so the calculator computes yours from the inputs above.

The Roth conversion calculator runs both versions side by side, so you don't have to pick one.

How long does a Roth conversion take to break even?

In the Roth conversion calculator's model, a Roth conversion only has a break-even year when you pay the tax from outside cash. With the tax withheld, both paths grow at the same rate, so the comparison does not change with time. Converting is ahead at every horizon when your future rate is above the effective rate on the conversion and behind at every horizon when it is below.

Paying from cash is different, because that cash would have kept growing in a taxable account and its gains would have been taxed. That drag adds up over time, so converting can catch up even when your future rate is a little below today's effective rate. A break-even year exists only for future rates between the effective rate times one minus your capital gains rate and the effective rate itself.

In the $100,000 worked example below, the effective rate is 15.5%. With 6% growth and a 15% capital gains rate, the floor is 13.2%, and at a 15% future rate converting comes out ahead after 5 years. Below 13.2%, it never does.

Comparing raw account balances pushes the break-even point decades later, because the traditional balance still owes income tax, so the Roth conversion calculator compares after-tax dollars instead. Change the assumed future federal rate in the Roth conversion calculator to see where your own break-even year falls.

Medicare IRMAA, and the two-year lookback

Conversion income raises your modified adjusted gross income, and Medicare reads MAGI from two years back. A conversion in 2026 sets your 2028 premiums.⁴

IRMAA is a cliff, not a ramp. One dollar over a threshold raises your premium for all twelve months of that year.

CMS has not published 2028 brackets or amounts yet, so the table below shows the current 2026 figures as a stand-in. Both the thresholds and the dollar amounts will move before 2028.

Converting before Medicare: The ACA premium tax credit

If you buy your own health coverage on an ACA marketplace before turning 65, a conversion's added MAGI can shrink or eliminate your premium tax credit for that year, raising your real out-of-pocket cost beyond the federal tax shown here. This calculator does not model the premium tax credit or its phase-out. If you receive one, check the effect separately before converting.

Social Security, capital gains, and the 3.8% investment income tax

Conversion income raises provisional income, which can pull up to 85% of your Social Security benefit into taxable territory.

Long-term capital gains and qualified dividends sit on top of ordinary income, so a conversion can push gains that would have been taxed at 0% into the 15% band. Both effects mean the marginal cost of a converted dollar can be higher than the bracket you are nominally in.

The conversion itself is not subject to the 3.8% net investment income tax, because distributions from IRAs and qualified plans are excluded from net investment income.⁵

It can still push your other investment income over the section 1411 thresholds of $200,000 for single filers and $250,000 for joint returns, which have never been indexed for inflation, so more people cross them every year.

When a Roth conversion can pay off

• Your rate this year is lower than the rate you expect when you withdraw, as it often is in the years between retiring and your first RMD. In any year you owe an RMD, it has to come out before you convert, and the RMD itself can never be converted.⁵ RMDs begin at 73 for people born 1951 through 1958 and at 75 for those born in 1960 or later, with the 1959 birth year still unresolved in the regulations, and the Tweed RMD calculator shows when yours starts. Test it with the assumed future federal rate.
• You can pay the tax from a taxable account, so the full converted amount reaches the Roth. Test it with the tax payment source toggle.
• You won't need the money for a long time, which gives tax-free growth more years to repay the tax. Test it with the years until withdrawal.
• You expect one spouse to file as single later. Single brackets are about half the width of joint brackets: in 2026 the 22% bracket ends at $105,700 of taxable income for a single filer vs $211,400 for a joint return.¹ Test it with the filing status.
• You plan to leave the account to heirs. The original owner of a Roth IRA never has to take distributions, and heirs who inherit one generally withdraw it tax-free once the five-year rule is met.⁵ Theinherited IRA 10-year rule sets how quickly most heirs have to empty the account.

When not to do a Roth conversion

• Your rate now is higher than the rate you expect in retirement, as in peak earning years. The Roth vs traditional guide covers that trade-off. Test it with the assumed future federal rate.
• The tax would have to come out of the IRA itself. Under 59½, the withheld amount also carries the 10% additional tax.⁵ Test it with the tax payment source toggle.
• You'll need the converted money within five years and you're under 59½. Each conversion has its own five-year period, starting January 1 of the conversion year.⁵
• The conversion would push your income over an IRMAA tier, the ACA premium tax credit limit, or into the senior deduction phase-out. The marginal rate chart in the calculator marks the IRMAA lines and steps up through the phase-out.
• Your heirs are likely to be in a lower bracket than you are now. Heirs must include taxable distributions from an inherited traditional IRA in their income, so they pay tax on what they withdraw, but at their own rates.⁵