Already have a grown Traditional IRA balance you want to convert instead of a fresh contribution? Use the Roth Conversion Calculator calculator, which models tax on investment growth too.
Already have a grown Traditional IRA balance you want to convert instead of a fresh contribution? Use the Roth Conversion Calculator calculator, which models tax on investment growth too.
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Good to Know
The pro-rata calculation aggregates every Traditional, SEP, and SIMPLE IRA balance you hold, per IRS rules -- it does NOT include a still-employer-held 401(k)/403(b) balance, which is excluded from the pro-rata pool entirely. This is a simplified same-year "contribute then immediately convert" model, not a full multi-year tax projection, and doesn't account for the conversion pushing you into a higher tax bracket for the year. Consult a tax professional before executing a backdoor Roth strategy.
Disclaimer
This calculator provides estimates for informational purposes only and does not constitute financial, medical, legal, or tax advice. Always consult a qualified professional about your specific situation.
How the Backdoor Roth Pro-Rata Calculation Works
A “backdoor Roth” contributes to a Traditional IRA (non-deductible, since income is too high)
and then immediately converts it to a Roth IRA — but the IRS pro-rata rule can make part of that
conversion taxable if you have any OTHER pre-tax IRA money anywhere. Enter your new
non-deductible contribution, any existing pre-tax Traditional/SEP/SIMPLE IRA balance, and your
marginal tax rate, and this calculator finds exactly how much of the conversion is taxable.
This is distinct from the Roth Conversion Calculator calculator, which converts an EXISTING
balance that has already grown — a backdoor Roth converts a brand-new contribution right away, so
the pro-rata rule (not investment growth) is the thing to watch for.
The Formula
The combined pool. The IRS treats every Traditional, SEP, and SIMPLE IRA you hold as ONE
account: your new non-deductible contribution plus any other pre-tax balance you already have.
The tax-free fraction. Per IRS Form 8606, the tax-free share of any conversion equals your
total non-deductible basis divided by the total pool:
taxFreePercent = contribution / (contribution + existingBalance).
Converting the whole pool. This calculator assumes the standard “clean” backdoor approach —
converting the entire pool at once. That produces a notable identity: the taxable amount always
works out to exactly your existing pre-tax balance, and the tax-free amount to exactly your new
contribution, regardless of the percentage.
Estimated tax. The taxable amount multiplied by your marginal tax rate gives a rough
estimate of the tax bill.
Worked Example
$7,500 new non-deductible contribution, with a $50,000 existing pre-tax Traditional IRA
balance, at a 24% marginal tax rate:
Combined pool: $7,500 + $50,000 = $57,500.
Tax-free fraction: $7,500 ÷ $57,500 ≈ 13.0%.
Since the entire pool converts, the taxable amount is exactly the existing balance: $50,000
is taxable, and $7,500 comes out tax-free.
Estimated tax: $50,000 × 24% = $12,000 — more than the entire $7,500 contribution itself.
Key Factors to Consider
The “aggregation” measures balances as of December 31 of the conversion year, not at the
moment you contribute. Even if your Traditional IRA is empty right when you make the
non-deductible contribution, any pre-tax IRA money you hold anywhere else by year-end still
counts toward the pro-rata pool for that tax year’s Form 8606 calculation.
The strategy works best when it’s genuinely quick — contribute, then convert soon after. The
longer the non-deductible contribution sits before conversion, the more it may grow, and any
growth beyond your own basis is taxable regardless of the pro-rata rule — a fast conversion
minimizes this separate, smaller tax exposure.
This is a legal, IRS-acknowledged strategy, not a loophole being exploited. The IRS’s own
Form 8606 instructions explicitly describe how to report a non-deductible contribution followed
by a conversion — the pro-rata rule exists precisely to prevent using this path to bypass income
limits with pre-existing pre-tax money, not to prohibit the strategy itself.
Once converted, the money follows normal Roth IRA rules, including the five-year rule for
withdrawals. A backdoor Roth conversion doesn’t get special treatment after the fact — the
converted funds are subject to the same Roth IRA rules (including potential early-withdrawal
considerations) as any other Roth conversion.
Interpreting Your Results
A large taxable amount here doesn’t mean the backdoor Roth strategy failed — it means the
pro-rata rule is doing exactly what it’s designed to do: taxing the pre-tax share of your combined
IRA balance on the way out, regardless of which account label you contributed the new money to.
Before executing anything, use the estimated tax figure to compare the actual after-tax value of
converting now against other options, such as first rolling pre-tax IRA money into an employer
plan (see below) or simply not converting until your other pre-tax balances are gone. This
calculator’s estimate uses your marginal tax rate for a single year — it doesn’t model the
conversion itself pushing you into a higher bracket, so a very large taxable amount may be taxed
at a higher real rate than what you entered.
Common Mistakes
Assuming only the new contribution is at risk. The IRS looks at your ENTIRE
Traditional/SEP/SIMPLE IRA balance, not just the specific dollars you say you’re converting.
Forgetting a 401(k) rollover already sitting in an IRA. An old employer plan rolled into a
Traditional IRA counts toward the pro-rata pool just like a deductible contribution would.
Not rolling pre-tax money into a 401(k) first. If your employer plan accepts rollovers,
moving pre-tax IRA money there BEFORE converting can eliminate the pro-rata problem entirely —
401(k) balances don’t count toward the pool.
Cómo Funciona el Cálculo del Prorrateo del Roth de Puerta Trasera
Un “roth de puerta trasera” contribuye a una IRA Tradicional (no deducible, porque el ingreso es demasiado alto) y luego la convierte de inmediato a una IRA Roth — pero la regla del prorrateo del IRS puede hacer que parte de esa conversión sea gravable si tienes CUALQUIER OTRO dinero pre-impuestos en una IRA en algún lugar. Ingresa tu nueva contribución no deducible, cualquier saldo pre-impuestos existente en una IRA Tradicional/SEP/SIMPLE, y tu tasa impositiva marginal, y esta calculadora encuentra exactamente cuánto de la conversión es gravable.
Esto es distinto de la calculadora Calculadora de Conversión Roth, que convierte un saldo EXISTENTE que ya ha crecido — un roth de puerta trasera convierte una contribución completamente nueva de inmediato, así que la regla del prorrateo (no el crecimiento de la inversión) es lo que hay que vigilar.
La fórmula
El fondo combinado. El IRS trata cada IRA Tradicional, SEP y SIMPLE que tengas como UNA sola cuenta: tu nueva contribución no deducible más cualquier otro saldo pre-impuestos que ya tengas.
La fracción libre de impuestos. Según el Formulario 8606 del IRS, la parte libre de impuestos de cualquier conversión es igual a tu base no deducible total dividida entre el fondo total: taxFreePercent = contribution / (contribution + existingBalance).
Convertir todo el fondo. Esta calculadora asume el enfoque estándar y “limpio” de puerta trasera — convertir todo el fondo de una vez. Eso produce una identidad notable: el monto gravable siempre resulta ser exactamente tu saldo pre-impuestos existente, y el monto libre de impuestos exactamente tu nueva contribución, sin importar el porcentaje.
Impuesto estimado. El monto gravable multiplicado por tu tasa impositiva marginal da una estimación aproximada de la factura de impuestos.
Ejemplo resuelto
$7,500 de nueva contribución no deducible, con un saldo pre-impuestos existente en una IRA Tradicional de $50,000, a una tasa impositiva marginal del 24%:
Fondo combinado: $7,500 + $50,000 = $57,500.
Fracción libre de impuestos: $7,500 ÷ $57,500 ≈ 13.0%.
Como todo el fondo se convierte, el monto gravable es exactamente el saldo existente: $50,000 son gravables, y $7,500 salen libres de impuestos.
Impuesto estimado: $50,000 × 24% = $12,000 — más que la contribución total de $7,500.
Factores clave a considerar
La “agregación” mide los saldos al 31 de diciembre del año de la conversión, no en el momento
en que contribuyes. Aunque tu IRA Tradicional esté vacía justo cuando haces la contribución no
deducible, cualquier dinero pre-impuestos de una IRA que tengas en cualquier otro lugar para
fin de año igual cuenta para el fondo de prorrateo en el cálculo del Formulario 8606 de ese año
fiscal.
La estrategia funciona mejor cuando es genuinamente rápida — contribuye, y luego convierte
poco después. Cuanto más tiempo permanezca la contribución no deducible antes de convertirse,
más puede crecer, y cualquier crecimiento más allá de tu propia base es gravable sin importar la
regla del prorrateo — una conversión rápida minimiza esta exposición fiscal separada y más
pequeña.
Esta es una estrategia legal y reconocida por el IRS, no un vacío legal que se esté
explotando. Las propias instrucciones del Formulario 8606 del IRS describen explícitamente cómo
reportar una contribución no deducible seguida de una conversión — la regla del prorrateo existe
precisamente para evitar usar este camino para eludir los límites de ingreso con dinero
pre-impuestos ya existente, no para prohibir la estrategia en sí.
Una vez convertido, el dinero sigue las reglas normales de una IRA Roth, incluida la regla de
los cinco años para retiros. Una conversión de roth de puerta trasera no recibe un trato
especial después del hecho — los fondos convertidos están sujetos a las mismas reglas de IRA
Roth (incluidas las posibles consideraciones de retiro anticipado) que cualquier otra conversión
Roth.
Cómo Interpretar Tus Resultados
Un monto gravable alto aquí no significa que la estrategia de roth de puerta trasera haya
fallado — significa que la regla del prorrateo está haciendo exactamente lo que fue diseñada
para hacer: gravar la parte pre-impuestos de tu saldo combinado de IRA al momento de salir, sin
importar bajo qué cuenta hiciste la nueva contribución. Antes de ejecutar cualquier cosa, usa la
cifra de impuesto estimado para comparar el valor real después de impuestos de convertir ahora
frente a otras opciones, como transferir primero el dinero pre-impuestos de la IRA a un plan del
empleador (ver más abajo) o simplemente no convertir hasta que tus otros saldos pre-impuestos
desaparezcan. La estimación de esta calculadora usa tu tasa impositiva marginal para un solo
año — no modela que la propia conversión te empuje a una categoría fiscal más alta, así que un
monto gravable muy grande podría gravarse a una tasa real más alta que la que ingresaste.
Errores comunes
Asumir que solo la nueva contribución está en riesgo. El IRS observa TODO tu saldo de IRA Tradicional/SEP/SIMPLE, no solo los dólares específicos que dices estar convirtiendo.
Olvidar una transferencia de 401(k) que ya está en una IRA. Un plan antiguo de un empleador transferido a una IRA Tradicional cuenta para el fondo de prorrateo igual que lo haría una contribución deducible.
No transferir el dinero pre-impuestos a un 401(k) primero. Si el plan de tu empleador acepta transferencias, mover el dinero pre-impuestos de la IRA allí ANTES de convertir puede eliminar por completo el problema del prorrateo — los saldos de 401(k) no cuentan para el fondo.
The IRS treats every Traditional, SEP, and SIMPLE IRA you own as ONE combined account when you convert any of it to a Roth -- you can't cherry-pick converting only your new, already-taxed non-deductible contribution. Only the fraction of the WHOLE pool that's your own already-taxed basis comes out tax-free; the rest is taxed as ordinary income, no matter which specific dollars you say you're converting.
How is this different from the Roth Conversion Calculator?
The Roth Conversion Calculator calculator models converting an EXISTING Traditional IRA balance that has already had time to grow -- the taxable part is largely investment gains. A backdoor Roth converts a NEW non-deductible contribution right away, before it grows, so ideally there is little or no investment gain to tax -- the pro-rata rule is the real risk here instead, not growth.
How can I avoid the pro-rata rule?
If your employer's 401(k) or similar plan accepts incoming rollovers, you can often roll your existing pre-tax Traditional IRA balance INTO that 401(k) first -- 401(k) balances are not part of the IRA pro-rata pool. Once your Traditional IRA holds only your new non-deductible contribution, converting it is fully tax-free. Not every 401(k) plan accepts rollovers, so check with your plan administrator first.
When exactly is my pre-tax IRA balance measured for the pro-rata rule?
As of December 31 of the year you do the conversion, not the moment you make the non-deductible contribution. Even if your Traditional IRA is empty right when you contribute, any pre-tax IRA money you hold anywhere else by year-end still counts toward the pro-rata pool on that year's Form 8606.
Is the backdoor Roth strategy legal?
Yes -- it's an IRS-acknowledged strategy, and Form 8606's own instructions describe how to report a non-deductible contribution followed by a conversion. The pro-rata rule exists specifically to prevent using this path to bypass income limits with pre-existing pre-tax IRA money, not to prohibit the strategy itself.
Do I have to file anything special with the IRS for a backdoor Roth?
Yes -- Form 8606 is required for the year of the non-deductible contribution and again for the year of the conversion (often the same year). It's what tracks your basis and reports the taxable and non-taxable portions of the conversion to the IRS -- filing it correctly is what keeps you from being taxed twice on the same already-taxed contribution down the road.
Does this calculator account for state income tax?
No -- the marginal tax rate you enter is whatever single combined rate you want to apply to the taxable amount, so you can enter a blended federal-plus-state rate yourself if your state also taxes the conversion as income. Not every state's tax treatment of a Roth conversion is identical, so check your own state's rules if this matters to your estimate.
What if I already have a Roth IRA -- does that affect the pro-rata calculation?
No -- an existing Roth IRA balance is never part of the pro-rata pool. The pro-rata rule only aggregates Traditional, SEP, and SIMPLE IRA balances (the pre-tax and non-deductible accounts), since those are the account types a backdoor Roth conversion actually draws from.
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