Roth Conversion Calculator
↻ Updated 2026Converting to a Roth adds to this year's taxable income. See the upfront tax cost, the tax-free balance it grows into by retirement, and the breakeven tax rate that tells you whether to convert.
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This is the side of the trade most conversion calculators leave out. The tax you pay today is visible and certain; the tax you avoid is a stream of forced distributions starting at 75 that grows with the balance and does not care whether you need the money. Converting shrinks that stream permanently — and unlike a traditional account, a Roth has no lifetime RMD at all.
Runs entirely in your browser — nothing you enter is sent to us.How this works
How to read your Roth conversion result
The number that decides this is the breakeven rate, not the tax-free value. Converting is a bet that your retirement tax rate will be higher than the rate you're paying to convert today — at the defaults that's 23.4%, and everything else on the page is scenery around that one comparison.
How the tax cost and breakeven of a Roth conversion are calculated
A conversion is treated as ordinary income in the year you do it. So the tax cost isn't the amount times a rate — it's the difference between two tax bills: what you'd owe on your income alone, and what you owe with the conversion stacked on top.
That stacking is why the cost is non-linear. The conversion lands on top of your existing income and fills whatever's left of your current bracket before spilling into the next, so the first dollars converted are cheaper than the last.
conversion tax = tax(income + amount) − tax(income) effective rate = conversion tax ÷ amount tax-free value = amount × (1 + return) ^ years breakeven rate = effective rate convert if you expect a higher rate in retirement
- amount
- What you move from a traditional IRA or 401(k) to a Roth — added to this year's ordinary income in full
- income
- Your taxable income before the conversion — after the standard or itemised deduction — not gross salary
- tax()
- 2026 federal ordinary-income tax for your filing status — IRS Rev. Proc. 2025-32 — federal only, no state tax anywhere in this model
- effective rate
- What the conversion actually cost, as a percentage — a blend of every bracket the conversion touched — always at or below your top bracket
- return
- Expected annual return, nominal — applied to the converted balance for the whole horizon
- years
- Time until you'd withdraw — scales both sides of the comparison identically — it can't change the breakeven
- breakeven rate
- The retirement tax rate at which converting and not converting tie — equal to the effective conversion rate — see the note below on why
Why breakeven equals the conversion rate: leaving the money in a traditional account means it grows by the same factor and gets taxed once at withdrawal. Converting means it's taxed once now. Multiplication is commutative, so paying r% at the front and paying r% at the back produce identical after-tax dollars — the years and the return cancel out entirely. That's why the horizon slider moves the headline but never the decision. Note the tension in the model, though: the tax-free value assumes you pay the tax from outside funds so the full $50,000 keeps compounding, while the breakeven assumes the tax comes out of the conversion. Both are defensible; they're just not the same scenario. See the traditional vs Roth calculator for the same algebra applied to contributions.
Worked examples
Example: converting $50,000 on $90,000 of taxable income, single
The calculator's defaults. Your taxable income puts you in the 22% bracket, and $50,000 of conversion pushes the top of it into the 24%.
| Tax on $90,000 alone2026 single brackets | $14,512 |
| Tax on $140,000income plus the conversion | $26,198 |
| Conversion taxthe difference — what the conversion costs | $11,686 |
| of which at 22%$15,700 fills the rest of the 22% bracket | $3,454 |
| of which at 24%$34,300 spills into the 24% bracket | $8,232 |
| Effective conversion ratebelow the 24% marginal rate | 23.4% |
| Tax-free value in 20 years$50,000 × 1.07 ^ 20 | $193,484 |
$11,686 now buys $193,484 of tax-free money in twenty years — but that framing is a sales pitch, not an analysis. The real result is 23.4%: convert if you believe your retirement rate will exceed it, don't if you don't. Note that $193,484 assumes you pay the $11,686 from a taxable account, not from the IRA.
Example: converting only $15,700 — filling the 22% bracket exactly
The same $90,000 of taxable income, but converting only up to the top of the 22% bracket, which for a single filer in 2026 ends at $105,700. Not a dollar spills into the 24%.
| Room left in the 22% bracket$105,700 − $90,000 | $15,700 |
| Conversion taxevery dollar taxed at 22% | $3,454 |
| Effective conversion ratedown from 23.4% — and it's a flat 22% | 22.00% |
| Tax-free value in 20 years$15,700 × 1.07 ^ 20 | $60,754 |
| Breakeven ratea lower bar to clear | 22.0% |
Converting a third as much drops the breakeven from 23.4% to 22.0%. That's the entire logic of the conversion ladder: each year you convert only what fits below a bracket edge, and repeat. The last $34,300 of the first example cost 24% — a rate you might never pay in retirement, and therefore the part of that conversion hardest to justify.
Frequently asked questions
Is a Roth conversion worth it?
It's worth it if your retirement tax rate will exceed the rate you pay to convert — 23.4% at the defaults — and it's a loss if it won't. Everything else is a refinement of that comparison.
The window most often cited is the gap between retiring and starting Social Security or RMDs, when income is unusually low and you control it. Other cases that come up: a low-earning year, a market drop that lets you convert more shares for the same tax, and estate planning, since heirs inherit a Roth free of income tax. Against it: money you'll need within five years is a poor candidate, because each conversion has its own 5-year clock before the converted principal can come out penalty-free (IRS Publication 590-B), and a conversion can't be undone — recharacterisation of conversions was eliminated by the Tax Cuts and Jobs Act.
Should I pay the Roth conversion tax from the IRA or from savings?
From outside funds, on the arithmetic — and the calculator's headline quietly assumes you do. Paying the $11,686 from a taxable account means all $50,000 converts and compounds to $193,484. Paying it from the IRA means only $38,314 lands in the Roth, growing to about $148,300 instead — roughly $45,000 of tax-free money forgone to cover a bill you could have paid another way.
Under 59½ the case is stronger still: dollars withheld from the IRA to cover tax are a distribution, not a conversion, and they can draw the 10% early-withdrawal penalty on top of the income tax. The practical mechanics are quarterly estimated payments or increased withholding from other income — and if the conversion is large enough, safe-harbour rules matter, since underpaying triggers a penalty regardless of what you owe in April.
What is the pro-rata rule for Roth conversions?
You can't convert only your after-tax IRA dollars. The IRS treats all your traditional, SEP and SIMPLE IRAs as one pool, and every conversion pulls a proportional slice of pre-tax and after-tax money — so if 90% of your combined IRA balance is pre-tax, then 90% of any conversion is taxable, no matter which account you draw from.
This calculator assumes the whole conversion is taxable, which is the correct default for anyone whose IRA money is entirely pre-tax. It's wrong for anyone with non-deductible basis, and it's the rule that most often ambushes a backdoor Roth. Two details worth knowing: the calculation uses balances as of 31 December of the conversion year, not the conversion date, and 401(k) balances are excluded from the pool — which is why rolling an old 401(k) into an IRA can create a pro-rata problem that didn't exist before.
Can a Roth conversion increase my Medicare premiums?
Yes, and it's the cost this calculator misses entirely. A conversion raises your MAGI, and Medicare's income-related monthly adjustment amount (IRMAA) uses a two-year lookback — so a 2026 conversion sets your 2028 Part B and Part D premiums.
What makes it dangerous is that IRMAA tiers are cliffs, not ramps: one dollar over a threshold triggers the full surcharge for the entire year, which makes the effective marginal cost of the last dollars of a conversion enormous. And a voluntary conversion isn't a qualifying life-changing event for the SSA-44 appeal, so there's no relief once it applies. For anyone 63 or older this is a live constraint that can outweigh the bracket arithmetic on the page above.
What this Roth conversion calculator ignores
The bracket arithmetic is exact for 2026 federal tax. Almost every real cost of a conversion sits outside it, and they all point the same way — conversions cost more than this page shows.
- IRMAA — Medicare surcharges are absent. A conversion that crosses an IRMAA threshold raises Part B and D premiums two years later, and because the tiers are cliffs, the marginal cost of the last dollar can dwarf the 24% the model charges it.
- No state tax — Federal brackets only. In a high-tax state the true conversion rate can be several points above the 23.4% shown, which moves the breakeven — sometimes decisively.
- The pro-rata rule — The whole conversion is treated as taxable. If you hold non-deductible basis in any traditional, SEP or SIMPLE IRA, your actual taxable portion is lower and the tax cost here is overstated.
- Two inconsistent assumptions — The tax-free value assumes the tax is paid from outside funds, so all $50,000 compounds. The breakeven rate assumes the tax comes out of the conversion. Both are reasonable framings; they just describe different transactions, and the page shows them side by side.
- One rate for all of retirement — Breakeven compares the conversion rate to a single future rate. Real withdrawals fill brackets from the bottom, so the fair comparison is against your future marginal rate on the last dollars — which is exactly what large RMDs and taxable Social Security tend to push upward.
- The five-year clocks — Each conversion starts its own 5-year period before the converted principal is penalty-free under 59½ — separate from the 5-year rule on Roth earnings. Neither appears in the projection.
- ·IRS Rev. Proc. 2025-32 — 2026 inflation adjustments — Tax year 2026 brackets & standard deduction
Rates, brackets and limits here are checked against primary sources. If a number still looks off, email support@realmoneyiq.com and we'll review and fix it.
RealMoneyIQ provides free educational calculators, not financial, tax, investment or legal advice. Results are estimates based on the assumptions you enter and publicly published rates; your actual outcome will differ. Always confirm decisions with a licensed professional who knows your full situation.