Roth Conversion Calculator 2026
Enter your income and a conversion amount to see the tax cost and your remaining bracket room instantly — then read how conversions work and when they pay off.
Quick answer
This calculator answers one question for the 2026 tax year: how much of a Traditional IRA or 401(k) can you convert to a Roth this year, and what does it cost? It works from taxable income — your income less your deduction — because that is what the tax brackets are measured against. The federal cost comes from the same engine as our Federal Tax Calculator; the state figure is a flat estimate shown on its own line.
Bracket room means the gap between your taxable income and the top of the bracket you are filling. A conversion is ordinary income, so it adds to taxable income dollar for dollar — which makes a dollar of bracket room a dollar of conversion room. It is not measured against AGI or MAGI, and your deduction is subtracted once, not twice.
Main assumption. One conversion in one year, with the rest of your income unchanged. The state figure is a flat rate on the converted amount, not a real state calculation.
Biggest limitation. It cannot tell you whether converting is worth it, because that depends on your tax rate decades from now. It shows this year's cost; the Lifetime Tax Savings calculator models the payoff over a whole retirement.
How these figures are calculated · IRS Pub. 590-A · Rev. Proc. 2025-32 · Tax data last verified
What each conversion size would cost
The same calculation at a ladder of amounts, so you can see where the cost stops being proportional. The highlighted row is the amount that exactly fills your selected bracket.
| Conversion | Federal tax | State estimate | Effective rate | Marginal rate after | Room left after | MAGI flag |
|---|---|---|---|---|---|---|
| $0 | $0 | $0 | 0.0% | 12.0% | $63,000 | clear |
| $10,000 | $1,200 | $500 | 17.0% | 12.0% | $53,000 | clear |
| $20,000 | $2,400 | $1,000 | 17.0% | 12.0% | $43,000 | clear |
| $30,000 | $3,600 | $1,500 | 17.0% | 12.0% | $33,000 | clear |
| $40,000 | $4,800 | $2,000 | 17.0% | 12.0% | $23,000 | clear |
| $50,000 | $6,000 | $2,500 | 17.0% | 12.0% | $13,000 | clear |
| $63,000fills the bracket | $7,560 | $3,150 | 17.0% | 12.0% | $0 | clear |
Every figure comes from the same calculation as the panel above, so the table and the calculator cannot disagree. Watch the effective rate: while a conversion stays inside one bracket it matches that bracket, and it starts to climb the moment a dollar spills over.
Understand your result
When you convert, the dollars you move from a Traditional IRA or 401(k) are added to your taxable ordinary income for the year and taxed at your marginal rates — there's no early-withdrawal penalty on a conversion. In return, the money grows tax-free in the Roth, comes out tax-free in retirement, and is exempt from required minimum distributions during your lifetime.
The strategy most retirees use is bracket filling: in a low-income year, convert just enough to reach the top of your current bracket. Beyond the tax you pay now, watch two side effects this tool flags — IRMAA (higher Medicare premiums about two years later) and the 3.8% net investment income tax — both driven by the higher MAGI a conversion creates. Paying the conversion tax from outside the IRA (with cash) makes the strategy far more effective, because every dollar keeps growing in the Roth.
This is exactly the scenario the calculator opens with: a married couple filing jointly, both aged 60 and so under 65, with $70,000 of ordinary income, converting $40,000 in a low-income year before required minimum distributions and Social Security start. Every figure below is produced by the same function as the panel above, from those same inputs — change an input and the panel moves; this example describes the defaults.
- Ordinary income before converting: $70,000
- No above-the-line adjustments, so AGI is also $70,000
- Less the 2026 married-filing-jointly base standard deduction of $32,200, plus $0 for age 65 or blindness — neither spouse is 65 — for a total deduction of $32,200
- Taxable income before converting: $37,800
- The 12.0% bracket runs to $100,800 of taxable income, so the total available room before the conversion is $100,800 − $37,800 = $63,000
- A $40,000 conversion fits inside that room — $40,000 of it uses the bracket and $0 spills above it — so every converted dollar is taxed at 12.0%: $4,800 of federal tax
- That leaves $23,000 of room still unused in the 12.0% bracket
- The effective federal rate on the converted dollars is 17.0% — the number to compare against your expected future rate. The 5.0% state estimate of $2,000 is a separate figure and is not part of that federal rate.
Change both ages to 66 and the calculator applies the age-65 addition: the deduction rises to $35,500, taxable income falls to $34,500, and the total available room grows to $66,300. That addition is a real, legitimate deduction and the calculator keeps it — it simply shows it on its own line now, so you can see exactly where the room comes from instead of being handed a figure $3,300 larger with no explanation.
- Converting so much you jump a bracket — watch the 'marginal bracket after' row.
- Paying the conversion tax from the IRA itself — pay from cash so the full amount keeps growing tax-free.
- Ignoring IRMAA — a big conversion can raise Medicare premiums two years later.
- Forgetting the pro-rata rule if you have after-tax (non-deductible) IRA money.
- Converting late in December with no time to fix an over-conversion (Roth conversions can't be undone).