Roth Conversion Calculator
Enter your income for the year and see how much room you have to convert before you cross into the next tax bracket, trigger a Medicare IRMAA surcharge, or lose part of an ACA subsidy.
Filing status
Your age
62Other taxable income this year
$40,000Everything before the conversion: Social Security, pension, withdrawals, dividends, after deductions.
Household size on the plan
Roth conversion this year
$40,000Your $40,000 conversion fits under that limit.
Estimated for a single tax year. IRMAA uses your income from two years ago, and the ACA premium is a national average, so your real numbers will differ. This doesn't account for RMDs or future years.
The three things that limit a Roth conversion
Your tax bracket
Every dollar you convert is taxed as ordinary income this year. Most people aim to fill up their current bracket and stop there, since the next bracket up costs more per dollar converted.
Medicare IRMAA
Medicare sets your Part B and Part D premiums based on your income from two years ago. A big conversion at 63 can raise your Medicare bill starting at 65, and the brackets are all-or-nothing, one dollar over the line and you pay the full surcharge for the year.
ACA subsidies
If you're retired before 65 and buying your own health insurance, a conversion raises your MAGI for the year, which can shrink your premium tax credit. For some people this costs more than the conversion saves in tax.
Why this is a one-year snapshot
This calculator answers "how much can I convert this year." It doesn't answer "how much should I convert across my whole retirement," because that depends on every other year too. Converting less now usually means a bigger required minimum distribution later, which can push you into a higher bracket for the rest of your life. Converting more now can mean a smaller RMD later, but it costs more today. The right balance depends on your full account balances, your age, and how many years you have before RMDs start at 73 (or 75, depending on your birth year).
ThunderHarbor's full projection runs this calculation for every year of your retirement, applying the same three checks, tax bracket, IRMAA lookback, and ACA subsidy, and finds the conversion amount each year that minimizes the total tax you pay over your lifetime.
Frequently asked questions
How much should I convert to Roth this year?
It depends on three things: how much room is left in your current federal tax bracket, whether the extra income would push your Medicare IRMAA tier up two years from now, and whether it would reduce an ACA subsidy if you are on a marketplace plan. The smallest of those three numbers is usually your practical limit.
Does a Roth conversion count toward IRMAA?
Yes. A Roth conversion is ordinary income and counts toward the MAGI Medicare uses to set your Part B and Part D premiums two years later.
Does a Roth conversion affect my ACA subsidy?
Yes, if you buy insurance on the ACA marketplace. A conversion raises your MAGI for the year, which can raise the share of income you are expected to pay toward your premium and lower your subsidy.
Is this a substitute for a full retirement projection?
No. This looks at one year in isolation. A full plan needs every year between now and when RMDs start, since converting more now can mean converting less, and paying less tax, later.