What a Roth Conversion Actually Is

A Roth conversion takes money sitting in a Traditional IRA — or a SEP, SIMPLE, or rollover IRA — and moves it into a Roth IRA, as described in IRS Publication 590-A. You can convert any traditional-type IRA, in any amount, in a single year. There’s no income limit on who can convert and no dollar limit on how much, which is the sharpest difference between a conversion and a regular Roth contribution. A conversion also doesn’t use up any of your annual IRA contribution room; you can contribute for the year and convert in the same year.

Whether a Roth account is the right home for your retirement savings in the first place is a separate question from whether to convert into one. If you haven’t settled that, our guide to Roth vs. Traditional IRA: Which One Is Better for You? walks through the trade-offs. This article assumes you already have money in a pre-tax IRA, or earn too much to contribute to a Roth directly, and are deciding whether to convert.

The Tax Bill: What a Conversion Costs You

The pre-tax portion of whatever you convert is added to your taxable income for the year and taxed at your regular income tax rates — the same rates that apply to your paycheck. There’s no special, lower rate for conversions, and no version of a conversion that avoids tax on pre-tax money. A large enough conversion can push part of your income into a higher bracket, so the size of the conversion matters as much as the decision to do one.

The one exception is money you’ve already paid tax on: basis, meaning nondeductible contributions you made to a Traditional IRA. Converting your basis isn’t taxed again. But if you also hold pre-tax IRA money anywhere, you can’t simply choose to convert the after-tax part first — the pro-rata rule, below, explains why.

Whatever the tax bill comes to, pay it from money outside the IRA if you can. Having the tax withheld from the converted funds themselves means less money lands in the Roth to grow tax-free — and if you’re under 59½, the withheld amount is generally treated as its own distribution, which can carry an additional tax on top.

Estimate Your Conversion Tax and Pro-Rata Split

Enter what you’re converting and what else you hold in pre-tax and after-tax IRA money, and this tool applies the pro-rata formula to estimate how much of the conversion is taxable and roughly what it will cost. It won’t compute your tax bracket for you — you supply your own marginal rate, because bracket thresholds change every year and a hardcoded number would go stale and quietly give you the wrong answer.

This tool applies the pro-rata formula to the figures you enter and multiplies by the rate you enter. It does not calculate brackets, state rules, surcharges, or your full tax picture — it’s an illustration, not tax advice.

The Pro-Rata Rule (The Trap That Catches Most People)

You can’t cherry-pick which dollars you convert. For pro-rata purposes, the IRS treats all of your Traditional, SEP, SIMPLE, and rollover IRAs as a single account, and every conversion is deemed to come proportionally from pre-tax and after-tax money across that whole pool — not just from the account you happen to convert. The proportion is based on your total IRA balances, measured at year-end.

This is why two people asking whether a backdoor Roth is worth it can get completely different answers. Someone with no other pre-tax IRA money can convert a nondeductible contribution and owe almost nothing. Someone with a large pre-tax IRA balance elsewhere will find that most of any conversion is taxable, even if the dollars they’re converting were just contributed after-tax.

Employer retirement plans, such as a 401(k), generally sit outside this aggregation. That’s why some people use a reverse rollover — moving pre-tax IRA money into an employer plan that accepts incoming rollovers — before doing a backdoor Roth, so the IRA left behind holds only after-tax basis. This is a widely used approach, not a guaranteed fix; it depends entirely on whether your employer’s plan accepts the rollover.

All of this gets reported on Form 8606, which also tracks your basis from year to year, as laid out in the Form 8606 instructions. Skipping it is how people end up paying tax twice on the same money — once on the pre-tax portion at conversion, and again later if the IRS has no record that some of it was already after-tax.

The Backdoor Roth — and Whether It’s Still Allowed

A “backdoor Roth” isn’t a separate account or a special IRS program. It’s a two-step sequence: make a nondeductible contribution to a Traditional IRA, then convert it to a Roth. It exists because contributions have income limits and conversions don’t — for 2026, direct Roth contributions phase out between $153,000 and $168,000 of modified adjusted gross income for single filers and heads of household, and between $242,000 and $252,000 for married couples filing jointly, but a conversion has no such ceiling.

Whether it’s worth doing depends entirely on the pro-rata rule above. For someone with no other pre-tax IRA money, a backdoor Roth can be nearly tax-free. For someone with a large pre-tax IRA balance, most of the conversion will be taxable, and the “backdoor” label doesn’t change that math. Report both the contribution and the conversion on Form 8606; tax software will generally walk you through entering it, but the form itself is what actually establishes your basis with the IRS.

A “mega backdoor Roth” is a different mechanism entirely — it involves after-tax contributions made inside an employer 401(k) plan and requires the plan to allow them, rather than converting an IRA.

The Five-Year Rule on Every Conversion

Each conversion starts its own five-year clock, separate from any other conversion you’ve made, per IRS Publication 590-B. If you withdraw a converted amount before that specific conversion’s five years are up, and you’re under 59½, an additional 10% tax can apply to that converted amount — even though you already paid income tax on it when you converted. The clock runs from January 1 of the year you convert.

This is a different rule from the five-year clock that governs tax-free earnings, which runs from the first year you funded any Roth IRA, by contribution or conversion, and never resets. Meeting that one determines whether your earnings come out tax-free; the per-conversion clock determines whether your converted principal comes out penalty-free.

Once you’re 59½ or older, reaching that age is itself an exception to the additional 10% tax, so the conversion clock generally stops mattering for the early-withdrawal penalty. If you’re already past 59½ and converted years ago, you’re very likely in the clear on this specific rule.

The Deadline: December 31, Not April

This is one of the most commonly, and expensively, misunderstood points in the whole topic. People who are used to funding an IRA up until tax season assume they have the same runway to convert. They don’t. A conversion counts for the calendar year in which the money actually lands in the Roth IRA, not the year you decide to do it.

In practice, that means starting well before December 31 — year-end processing at financial institutions slows down, and a transfer initiated in the last days of the year can land in January instead, pushing the taxable event into the following year whether you intended that or not.

When Does It Make Sense to Do a Roth Conversion?

These are common considerations, not a personal recommendation — your own numbers decide this, ideally with a tax professional.

A conversion probably makes sense if…

• This year’s income is unusually low — a gap year, early retirement before Social Security and RMDs begin, a business loss, or a year with large deductions.
• You expect meaningfully higher tax rates later, whether from your own income trajectory or from RMDs eventually forcing large withdrawals.
• Reducing future required withdrawals matters to you — a Roth IRA has no RMDs for the original owner. See our RMD 2026: Age, Tables, and How to Avoid the Taxes guide for what those withdrawals actually look like.

Probably wait if…

• You’d have to pay the conversion tax out of the IRA itself.
• You expect a materially lower tax rate in retirement than you’re in now.
• You’ll need the money within five years and you’re under 59½.
• The added income would push you over a threshold that costs more than the conversion saves.

The Conversion Ladder

Some people convert a planned amount each year, on purpose, so that once each year’s amount clears its own five-year clock, it becomes available to withdraw penalty-free before traditional retirement age. This “conversion ladder” is mainly a tool for people retiring earlier than 59½ who need a bridge of accessible money; it takes planning several years out and isn’t something to start without mapping the whole ladder first.

Converting a 401(k) to a Roth IRA

The same taxable-event logic applies if the money you’re converting started in an employer 401(k) rather than a Traditional IRA: the pre-tax portion becomes ordinary income in the year of the conversion. The mechanics of getting money out of a 401(k) and into an IRA first are their own topic and aren’t covered here.

The Hidden Costs Nobody Mentions

Converting doesn’t just raise this year’s tax bill in isolation — it raises your modified adjusted gross income (MAGI), and MAGI touches things people don’t expect a retirement account decision to touch.

• Medicare premiums. Higher MAGI can trigger IRMAA surcharges on Medicare Part B and Part D. The Social Security Administration generally uses your income from two years earlier to set the surcharge, so a conversion this year can raise your premiums two years from now. See IRMAA 2026 Brackets: How to Avoid the Medicare Surcharge for the current thresholds.
• Social Security. Added income from a conversion can increase the taxable share of Social Security benefits you’re already receiving.
• Marketplace subsidies. If you buy health coverage through the ACA marketplace, a conversion can reduce or eliminate a premium subsidy for that year.
• State income tax. Most states tax conversion income too, and treatment varies by state — check your own state’s rules before finalizing an amount.

None of this makes a conversion a bad idea. It means the size of the conversion matters as much as the decision to do one — a smaller conversion that stays under a threshold can beat a larger one that trips it.

Can You Undo a Roth Conversion?

No. Recharacterizing a Roth conversion — treating it as if it never happened — was eliminated for conversions made in 2018 and later, as confirmed in the IRS’s IRA FAQs on recharacterization. Before that change, you could reverse a conversion if the market dropped or your income came in higher than planned. That option is gone. Once you convert, it’s permanent.

That’s different from recharacterizing a contribution, which is still generally available. If you contributed to a Roth IRA for the year and later discover your income was too high to be eligible, you can typically recharacterize that contribution as a Traditional IRA contribution instead. A large number of people searching for “Roth to Traditional” conversion are actually asking about this contribution fix, not about reversing a conversion — they’re two different transactions with two different outcomes.

Because a conversion can’t be undone, many people convert smaller amounts over several years instead of moving everything at once. Spreading it out limits how wrong a single year’s guess about income or rates can go.

How to Convert, Step by Step

The mechanics are the same regardless of which institution holds your IRA — you request the conversion through whichever firm holds the account.

1. Decide the amount, using the tax cost and hidden-cost sections above to avoid tripping a threshold you didn’t mean to cross.
2. Confirm your basis and your total balance across every Traditional, SEP, SIMPLE, and rollover IRA you own — pro-rata treats them as one account.
3. Open a Roth IRA if you don’t already have one.
4. Request a direct transfer from the Traditional IRA to the Roth IRA through the institution holding the funds.
5. Arrange to pay the resulting tax from money outside the IRA, and consider whether an estimated tax payment is needed for the quarter to avoid an underpayment penalty.
6. File Form 8606 with your tax return to report the conversion and update your basis. Most tax software handles the entry once you know the numbers; the form itself is the record that keeps the IRS from taxing the same basis twice.

You’ll typically receive a Form 1099-R reporting the distribution from the Traditional IRA and a Form 5498 reporting the contribution to the Roth IRA — keep both with your tax records.

Frequently Asked Questions

What is a Roth conversion?

Moving money from a Traditional, SEP, SIMPLE, or rollover IRA into a Roth IRA, with the pre-tax portion taxed as ordinary income in the year you convert.

How much tax will I pay on a Roth conversion?

The pre-tax amount you convert is taxed at your ordinary income tax rate for that year; use the calculator above for an estimate based on your own numbers.

Is there a limit on how much I can convert?

No. Conversions have no income limit and no dollar cap, unlike regular Roth contributions.

What is the deadline for a Roth conversion?

December 31 of the tax year — not the following April’s filing deadline, which only applies to contributions.

What is the pro-rata rule?

All your Traditional, SEP, SIMPLE, and rollover IRAs are treated as one account for conversion purposes, so you can’t choose to convert only your after-tax basis; every conversion is proportional to your total pre-tax and after-tax balances.

Is the backdoor Roth still allowed?

Yes, as of August 13, 2026. There’s no federal law prohibiting the contribute-then-convert sequence, though it has repeatedly been the target of legislative proposals, so it’s worth re-checking its status periodically.

Does every conversion have its own five-year rule?

Yes. Each conversion starts a separate five-year clock for penalty purposes, distinct from the five-year clock on Roth earnings.

Does the five-year rule still apply if I’m over 59½?

Generally no, for the early-withdrawal penalty — reaching 59½ is itself an exception to that additional tax.

Can I undo a Roth conversion?

No. Recharacterizing a conversion was eliminated for conversions made in 2018 and later; it’s permanent once completed.

Should I pay the tax out of the converted money?

Generally no — paying from outside the IRA keeps the full converted amount growing tax-free, and withholding from the conversion itself can trigger an additional tax if you’re under 59½.

Will a conversion raise my Medicare premiums?

It can, through IRMAA, with a two-year lookback on the income that triggers it — a conversion this year can raise premiums two years from now.

Do I need to file Form 8606?

Yes. Form 8606 reports the conversion and tracks your basis; skipping it is a common way people end up taxed twice on the same money.