This calculator shows what converting a chosen amount to a Roth would cost you this year: federal and New York tax on the conversion, how much room is left in your current bracket before it pushes you into the next one, how the New York pension and annuity exclusion applies, and what it does to your Medicare premium two years later.
What would a Roth conversion cost me this year?
The years between retiring and the first required distribution are the low-income years of a lifetime, and they are when a conversion is cheapest. This works out the federal and New York tax on a conversion you choose, and what it does to your Medicare premium two years later. It does not tell you whether to convert.
Taxable income is line 15 of Form 1040. Modified adjusted gross income is line 11 plus any tax-exempt interest; it is the figure Medicare uses, and it is normally the larger of the two.
Federal brackets from IRS Revenue Procedure 2025-32. New York rate schedule from Form IT-2105-I for 2026. The $20,000 pension and annuity exclusion and its application to conversion income from TSB-M-98(7)I. Medicare amounts from the Centers for Medicare and Medicaid Services.
How it works
It costs you tax now to stop taxing it later
A conversion moves money from a pre-tax account into a Roth. You pay income tax on the amount converted in the year you convert it, and what is in the Roth afterwards is not taxed again, is not subject to required minimum distributions in your lifetime, and passes to heirs without income tax.
This tool does not tell you whether to convert. It tells you what the bill is. It does not project growth and it does not compare outcomes, because doing so would require assuming a rate of return and a future tax rate, and the answer would then be a function of those assumptions rather than of the law.
The two edges that catch people
The bracket edge. A conversion that crosses into a higher federal bracket is taxed at that higher rate on the part above the line, not on the whole. The calculator shows how much room is left before that happens, which is usually the figure people actually want.
The Medicare edge, two years out. Medicare premiums are set from the income you reported two years earlier, and they move in steps rather than smoothly. A conversion that pushes you a dollar over a threshold moves you a whole bracket. The calculator gives the exact amount that would stay under the next edge.
One New York point worth knowing
New York treats conversion income as qualifying for the $20,000 pension and annuity income exclusion from age 59 and a half. That is stated in TSB-M-98(7)I, and the calculator applies it. It is not the same in every state, and the New Jersey treatment is genuinely unsettled.
Questions
Common questions
Can I undo a conversion?
No. Recharacterisation of Roth conversions was repealed for conversions made after 2017. The decision is final once made, which is why the December version of this question is a different question from the January one.
Does the five-year rule apply?
Each conversion carries its own five-year clock before the converted amount can be withdrawn without penalty if you are under 59 and a half. The tool does not model that, and it matters most for people converting close to retirement rather than well before it.
Several of these choices cannot be undone.
A conversion is permanent, it interacts with your Medicare premium two years out, and the right amount is rarely the round number people start with. We can cover it in a short conversation, at no charge and with no obligation.
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