How much should you convert to Roth on $40k?
On $40,000 filing single, your taxable income is $23,900 and you are in the 12% bracket with $26,500 of room before the 22% bracket begins. Converting that $26,500 would cost $3,180 in federal tax, all of it at 12%. Converting more than that pushes the excess into the 22% bracket, which is where the case for converting usually stops.
A conversion moves money from a pre-tax account to a Roth and you pay ordinary income tax on it now, at your marginal rate, so that it is never taxed again. The whole question is whether the rate you pay today is lower than the rate you would pay later. Everything else is detail.
That makes the useful number your HEADROOM: how much more income you can add before the next bracket starts. On $40,000 filing single it is $26,500, and filling it costs $3,180. Convert more and the excess is taxed at 22% instead of 12%, which is usually where the argument stops making sense.
Look along the table before assuming yours is typical. The room is not proportional to income and it is not intuitive: someone can earn far more than you and have far more room, simply because they sit at the bottom of a wide bracket while you sit near the top of a narrow one. It is also why this is a decision to re-make every year rather than a plan to set once.
Now the part almost nothing covers, which is when NOT to convert. A skipped year is not a year you forgot. It is frequently the correct answer, and there are four common reasons.
First, your income is already high. Converting at 12% only helps if your later rate would be higher, and for a year like this one it often would not be. Second, before 65 a conversion raises the income that ACA premium credits are measured against, and crossing 400% of the poverty level removes the credit entirely rather than tapering it. The tax on the conversion can be the smaller half of what it costs you.
Third, from 63 a conversion raises Medicare premiums two years later, because IRMAA works off a two-year lookback. Fourth, and most often missed: if you have to pay the conversion tax OUT OF the converted money, you have shrunk the balance you were trying to protect and given up part of the growth you were converting for. A conversion works best when the tax comes from somewhere else.
The window where this is most worth doing is the gap between retiring and claiming Social Security, when your income is at its lowest and the whole low-bracket space is available. That is also when the pre-tax balance is still compounding toward required minimum distributions at 73, which is the thing a conversion is ultimately defusing.
Your income this year vs outcome
The same question at every your income this year, so you can use the one you believe.
| Your income this year | Room before the next bracket |
|---|---|
| $40,000this page | $26,500 at 12% |
| $60,000 | $6,500 at 12% |
| $80,000 | $41,800 at 22% |
| $120,000 | $1,800 at 22% |
| $180,000 | $37,875 at 24% |
Filing single for 2026, standard deduction $16,100, and this is your only income. Notice the room is NOT proportional to income: it depends on where you sit inside a bracket, which is why the answer changes every year.
Assumptions
- Income
- 40000
- Married
- 0
- Standard Deduction
- 16100
- Taxable Income
- 23900
- Current Marginal Rate
- 12%
- Bracket Ceiling
- 50400
- Headroom
- 26500
- Tax To Fill Bracket
- 3180
- Next Bracket Rate
- 22%
- Rmd Start Age
- 73
- Tax Year
- 2026 yr
Frequently asked
How much should I convert to Roth on $40k a year?
Up to $26,500 keeps the whole conversion inside the 12% bracket and costs $3,180. Beyond that the excess is taxed at 22%. Filling the bracket and stopping is the usual rule.
When should I NOT convert?
Four cases. Your income is already high, so today's rate is not lower than your later one. You are under 65 and on a marketplace plan, where the extra income can cost an entire premium tax credit. You are 63 or older, where it raises Medicare premiums two years later. Or you would have to pay the tax out of the converted money, which defeats the purpose.
Why does a skipped year appear in my schedule?
Because skipping was the better answer that year, not because nothing happened. A conversion is only worth doing when the rate you pay now is below the rate you would pay later, and in some years it is not. A schedule that converted every year regardless would be following a rule rather than doing the arithmetic.
Should I pay the tax from the IRA itself?
Preferably not. Paying from the converted balance shrinks the amount that moves into the Roth and gives up the future growth on the part you spent, so the conversion does less of what you wanted. If outside cash is not available, that alone is a reasonable reason to convert less or to wait.
Is there a best time of year to do it?
Late in the year, once your actual income is close to known. Converting in January means guessing your own headroom, and a conversion cannot be undone: recharacterisation of conversions was removed in 2018, so an over-conversion stays over-converted.
Keep going
Rightmont sizes each conversion to your bracket, year by year, and tells you which years it skipped and why. Model it free.
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