Roth Conversion Calculator

How a Roth conversion works

A conversion moves money from a traditional IRA or 401(k) into a Roth account. You pay ordinary income tax on the amount this year, and in exchange that money — and everything it earns from here — comes out tax-free later and is never subject to required minimum distributions. There is no age limit, no income limit, and no penalty for converting at any age.

The question is never really whether to convert. It is how much to convert in any one year, because the tax is paid at your marginal rate and the rate climbs in steps.

Fill the bracket, don't spill out of it

The standard approach is to convert exactly enough to reach the top of the bracket you are already in. The classic window is the stretch between retiring and the year RMDs begin: earned income has stopped, Social Security may not have started, and taxable income is often at the lowest point it will ever reach. Every dollar converted in those years at 12% or 22% is a dollar that will not be forced out later, potentially at a higher rate, as part of a required minimum distribution.

A converted dollar can cost more than a dollar

Conversions rarely raise taxable income by exactly the amount converted. Two effects pile on. More of your Social Security becomes taxable as provisional income rises — up to 85% of benefits. And the 2026 senior deduction phases out as income climbs, so part of your deduction disappears as you convert. That is why this calculator searches for the conversion amount that lands on a threshold rather than subtracting your income from it: the relationship is not one-to-one, and the effective rate on a conversion is often several points above your nominal bracket.

Watch the Medicare threshold too

Because a conversion inflates modified adjusted gross income, it can push you across an IRMAA tier and raise your Medicare premiums — two years later, which is long enough that people forget the connection. IRMAA is a cliff: one dollar over costs the full surcharge for that tier, for both spouses if both are enrolled. For anyone on Medicare or within two years of it, the IRMAA line often binds before the tax bracket does, which is why both appear side by side in the table above.

Two deadlines that cannot be undone

A conversion counts in the calendar year the money leaves the traditional account — there is no grace period into the following April the way there is for IRA contributions. And since 2018 a conversion cannot be recharacterized: once done, the tax is owed even if the market falls the next week. Size it before you move the money. One last ordering rule: if you are old enough to owe an RMD this year, that distribution must be taken first and cannot itself be converted.

Frequently asked questions

How much should I convert in one year?

The common approach is to fill your current tax bracket without spilling into the next one, while staying under the next Medicare IRMAA threshold. That turns an open-ended question into two concrete numbers, which is what the calculator above computes from your own income.

How is a Roth conversion taxed?

The converted amount is ordinary income in the year you convert, taxed at your marginal rates. There is no early-withdrawal penalty on a conversion regardless of age. Because the conversion raises your adjusted gross income, it can also pull more of your Social Security into taxable income and shrink income-tested deductions — so the true cost is often higher than the amount times your bracket rate.

Can I undo a conversion if I convert too much?

No. Recharacterizing a conversion was eliminated for conversions made in 2018 and later. Once the money moves, the tax is owed, which is why it pays to size the conversion before making it rather than after.

Does a conversion count toward my RMD?

No, and the order matters. If you are old enough to owe a required minimum distribution, that distribution must be taken first, and it cannot itself be converted. Only amounts above the RMD are eligible to move into a Roth.

When is the deadline?

December 31 of the tax year. Unlike an IRA contribution, a conversion cannot be made after year-end and applied to the prior year — a conversion completed in January counts on that new year’s return.

Do I have to wait five years to use the money?

Each conversion starts its own five-year clock. Withdraw converted principal before that clock runs out and before age 59½, and a 10% penalty applies to it. After 59½ that particular rule no longer bites, though earnings still require the account to have been open five years to come out entirely tax-free.