Roth Conversion Calculator (US)

Roth Conversion Strategy Guide

What is a Roth Conversion?

A Roth conversion moves money from a Traditional IRA / 401(k) (pre-tax) to a Roth IRA (post-tax). The amount converted is added to your taxable income for that year. You pay tax now at your marginal rate. In exchange, the money grows tax-free FOREVER and qualified withdrawals after age 59½ are tax-free. There's no income limit on conversions (unlike Roth contributions). No conversion limit either — you can convert any amount. The decision is fundamentally about tax-rate arbitrage: pay tax now versus later, betting on whether your tax rate today is lower than it will be in retirement.

When Conversions Make Sense?

Strong cases for conversion: (1) Low-income year — gap years between retirement and Required Minimum Distributions (RMDs at 73) are prime conversion windows. (2) Bear market — convert when account values are depressed, future recovery happens tax-free. (3) Estate planning — Roth IRAs have no RMDs during owner's lifetime; heirs inherit tax-free (10-year drawdown rule). (4) Expecting higher future tax rates — TCJA expires end of 2025; tax rates may rise. (5) Want tax diversification — splitting between Traditional and Roth accounts to hedge against uncertainty about future tax rates and rules.

What do I need to know about The Roth Conversion Ladder (FIRE Strategy)?

Early retirees in the FIRE community use conversion ladders to access retirement money before 59½ without 10% penalty. Strategy: (1) Retire at, say, 45 with $1M in 401(k). (2) Roll 401(k) to Traditional IRA. (3) Each year, convert $40,000 from Traditional to Roth. Pay tax at low rate (no other income). (4) Wait 5 years — conversions can be withdrawn penalty-free after 5 years from Roth (the seasoning rule). (5) At age 50, start withdrawing the conversions you made at age 45. Continue rolling the ladder forward each year, converting a new batch 5 years before you plan to withdraw it, to access retirement funds penalty-free before the standard retirement age.

What should I know about Conversion Gotchas?

Watch out for: (1) Medicare IRMAA surcharges — higher income from conversions raises Medicare Part B/D premiums 2 years later for those 63+ converting. (2) Social Security taxation — conversions can push more SS into the 85%-taxed bracket. (3) ACA subsidies — pre-Medicare retirees on ACA marketplace plans lose subsidies as conversion income rises. (4) Pro-rata rule — if you have any deductible Traditional IRA money, you can't selectively convert non-deductible portion. (5) No recharacterization allowed since 2018 — once a conversion is made, it cannot be reversed if your circumstances or tax situation change, so plan conversions carefully before executing them.

What a Roth Conversion Actually Does and Why People Choose to Pay Tax Early

A Roth conversion moves money from a traditional, pre-tax retirement account into a Roth account, triggering ordinary income tax on the converted amount in the year of conversion, in exchange for all future growth and qualified withdrawals being entirely tax-free from that point forward. The core bet behind any conversion is that paying tax now, at today's known rate, will end up cheaper than paying tax later on withdrawals, at a future rate that might be higher — whether due to rising tax rates generally, required minimum distributions pushing you into a higher bracket in retirement, or simply having grown the account substantially by the time you'd otherwise withdraw it. Conversions are especially attractive in years of unusually low taxable income, such as an early-retirement gap year before Social Security and required distributions begin, when the conversion can be taxed at a historically low marginal rate.

Why "Filling Up" a Tax Bracket Is the Common Conversion Strategy

Rather than converting a large traditional balance all at once — which risks pushing a big chunk of the conversion into a much higher marginal tax bracket in a single year — many people convert smaller amounts annually, calculated specifically to "fill up" the current tax bracket without spilling into the next one. Done over several years during a lower-income window, this strategy can convert a meaningful traditional balance over time while keeping each year's conversion taxed at a comparatively low marginal rate, rather than facing one enormous tax bill in a single year. It's also worth factoring in any Medicare IRMAA thresholds for those near that age, since a large conversion can trigger higher Medicare premiums two years later even where the income tax impact alone seems acceptable.

The Five-Year Rule Each Conversion Starts

<p>Every Roth conversion starts its own five-year clock, separate from the five-year rule that applies to Roth contributions and separate from any other conversion made in a different year. Withdraw converted funds before that specific conversion's five years are up and before age 59½, and the converted amount can be hit with a 10% early withdrawal penalty, even though the conversion itself was already a taxable event. This matters most for anyone using the 'Roth conversion ladder' strategy to access retirement funds early, since each year's conversion needs to season for five years before it can be withdrawn penalty-free, meaning the ladder has to be started years ahead of when the money is actually needed. It also matters for anyone converting in multiple tranches over several years as part of ordinary tax-bracket management — tracking which converted amount belongs to which year's five-year clock becomes necessary record-keeping, since the IRS applies ordering rules to determine which dollars are considered withdrawn first.</p>

US Tax Brackets and the 'Fill the Bracket' Strategy

The core Roth conversion strategy is converting just enough traditional IRA or 401(k) money each year to use up the remaining space in a lower tax bracket, without pushing income into the next one up. The table shows (illustrative, check current-year figures) how much headroom a retiree might have in a given bracket.

A retiree with, say, $30,000 of other taxable income (Social Security, pension, interest) filing jointly has roughly $64,000 of headroom remaining in the 12% bracket before crossing into 22%. Converting exactly that amount each year — rather than converting a large lump sum that jumps straight into the 22% or higher bracket — means every dollar converted is taxed at 12% rather than a blended higher rate. This is why Roth conversion strategies are usually planned as a multi-year ladder rather than a single large event: spreading a large traditional balance across several years of "filling the bracket" minimizes the average tax rate paid on the whole conversion.

Worked Example: A Four-Year Conversion Ladder

A retiree has $240,000 in a traditional IRA and wants to convert it to a Roth over several years to manage the tax bill, rather than converting it all in one year (which could push a large chunk of it into a 24% or even 32% bracket). Based on their other income, they calculate they have roughly $60,000 of headroom in the 12% bracket each year. Converting $60,000 a year for four years converts the full $240,000, each year's conversion taxed at 12% — total tax of $28,800 across the four years (ignoring that marginal rates could shift slightly year to year with inflation adjustments). Compare that to converting the full $240,000 in one year: the first $60,000 might still get the 12% rate, but the remaining $180,000 would push well into the 22% and possibly 24% brackets, with a blended effective rate on the full conversion of perhaps 19-21% rather than a flat 12% — total tax of roughly $45,600 to $50,400, some $17,000-$22,000 more than the laddered approach for exactly the same amount converted. This is the single biggest lever in Roth conversion planning: the tax cost depends heavily on pacing, not just on the total amount converted or the account's investment performance.

Roth Conversions and Medicare IRMAA Surcharges

For those near or over 63, a Roth conversion has a side effect that's easy to miss: it counts as taxable income in the year of conversion, and Medicare's Income-Related Monthly Adjustment Amount (IRMAA) looks back two years at that income to set higher Part B and Part D premiums. A conversion large enough to push modified adjusted gross income over an IRMAA threshold can trigger a surcharge that applies for a full year, sometimes adding well over a thousand dollars annually in extra premium between two people — a real cost that a simple 'tax bracket' calculation of the conversion itself won't capture. This is a strong reason some retirees deliberately convert smaller amounts over more years, or do most of their converting before age 63, rather than one large conversion that looks efficient on a tax-bracket basis alone but trips an IRMAA threshold two years later.