Roth Conversion State Tax Calculator: What Your State Adds, and What Lands in the Roth

Guides › Roth Conversions

Updated August 21, 2026. Quick answer: whether your state taxes a Roth conversion is a yes-or-no question, and it is the wrong one to stop at — what decides anything is the size of the bill. Put your own figures in below and this returns four numbers: what the state takes, what the federal bill is beside it, what share of the total the state line actually is, and how much of the conversion reaches the Roth once the tax is paid. It will also price the same conversion against a second state if a move is on the table. Every figure is arithmetic on rates and amounts you supply. No rate, cap or threshold is quoted at you here — your state’s rule, with the statute or revenue-department guidance that says so, is on the 51-jurisdiction table, and that is where the rate you type in should come from.

The calculator

Where each number comes from

Four of the six inputs are lookups rather than guesses, and none of them is a figure this page is entitled to invent for you.

Your state’s rate on conversion income. Start at the 51-jurisdiction table, which gives each state’s answer with the statute or revenue-department guidance behind it, then open your own state’s page for the detail. Three things there change the number you type: some states have no income tax at all, so the rate is zero; some tax the conversion at a flat rate; and some run graduated rates, in which case the figure you want is the rate on the band the conversion lands in, not the bottom of the schedule.

The exclusion you still have available. This is the input people get wrong, and it is worth ten minutes. A state retirement-income exclusion is not a discount on your conversion — it is a cap, and your pension, your annuity and any distributions you have already taken this year consume it first. What is left is what shelters the conversion. Two further traps: several states gate the exclusion by age, so converting before a birthday can cost materially more than converting after it, and several others expressly deny the exclusion to conversion income even though they allow it on ordinary withdrawals. Your state’s page says which case you are in. If you are not certain, enter 0 — the result is then the conservative one.

Your federal marginal rate. The conversion is federal ordinary income first, and for most converters the federal line is the larger of the two by some distance. If you do not know which bracket the conversion lands in, work out how much room your bracket has left before you come back here, and read what a conversion actually costs at the federal level if the mechanics are new to you.

Where the tax is paid from. Not a lookup but a decision, and it is the one that changes what you end up with rather than what you owe. Withholding the tax out of the conversion shrinks the balance that was the entire point of converting — why paying from outside the account is usually the difference between a conversion that works and one that does not. If you are paying from outside, the bill is also not due next April in one lump for everyone: the estimated-tax timing is its own question.

What this calculator deliberately leaves out

Brackets. Both rates you enter are applied flat to the whole conversion. Real tax is marginal: a conversion large enough to matter climbs through bands, so a single rate typed at the bottom of the climb understates the bill and one typed at the top overstates it. This is the calculation’s main simplification and it is deliberate — modelling brackets properly needs your full return, not four inputs. For the federal side, the bracket calculator does that job.

Everything a conversion touches other than income tax. A conversion raises the income figure that several unrelated systems read. It can lift your Medicare premiums two years later (the IRMAA cliffs and the two-year lag), change how much of your Social Security is taxable (the interaction), and push you over an ACA subsidy threshold if you are covered on the exchange (the cliff). None of those is in the arithmetic above, and any of them can be larger than the state line it prices.

Local and part-year tax. Some states let cities, counties or school districts levy their own income tax on top of the state rate; enter a combined rate if that applies to you, because the calculator has no way to know. And a year in which you move is not a year with one state rate in it — a part-year return apportions income between two states, and the comparison above deliberately shows the two states side by side rather than pretending to run that split for you.

Whether to convert at all. Nothing here says the conversion is a good idea. It prices the tax on one you have already decided to consider. The case for and against — and the five signals that actually decide it — is a separate question, and a conversion cannot be undone once it is made.

What the state answer does not decide

The state line is the smaller half for most converters, and it is worth being plain about that on a page built to compute it. A state with no income tax removes one number from the arithmetic; it does not make a conversion the right size, or this the right year to do it.

Three things move more money than the state rate usually does. Which year you convert in — a year with unusually low other income, a gap year between salary and Social Security, or a market that has fallen, so the same shares convert for less tax. How much you convert at once, which is a bracket question rather than a state one. And where the tax money comes from, which the calculator above already shows you.

If your state is one of the ones that shelters part of a conversion, there is a fourth: your age at the moment you convert, because several of those shelters are gated on a birthday. That one is on your state’s own page, and it is the single most common reason a conversion costs more than the converter expected.

Methodology

The arithmetic, in full, so you can check it. Sheltered = the smaller of the conversion and the exclusion you entered. State taxable = conversion − exclusion, floored at zero. State tax = state taxable × your state rate. Federal tax = the whole conversion × your federal rate, with no exclusion applied, because a state retirement-income exclusion is a state-level subtraction and does not reduce federal income. Total = state + federal; the effective rate is total ÷ conversion, and the state share is state tax ÷ total. What lands in the Roth = the whole conversion where the tax is paid from outside, or conversion − total tax where it is withheld from the conversion. The two-state comparison runs the state half of that calculation twice, once with each state’s rate and exclusion, and reports the difference; it does not apportion anything, because a part-year split is not arithmetic this page can do honestly.

Figures verified against the page’s own methodology arithmetic and SSA POMS HI 01101.020 (the two-year look-back for Medicare income-related surcharges) on September 30, 2026, because the page quotes no official rate, cap or threshold; the state rules on the linked 51-jurisdiction table were not re-checked.

Nothing is fetched, stored or sent anywhere: the calculation runs entirely in your browser on the values you type, and this page has no server that ever sees them. It quotes no state’s rate, cap or threshold, deliberately — those change by legislative session and the only figures that govern your conversion are the current ones for your state, which the 51-jurisdiction table carries with its citations.