Transparent method
The formula
Worked example
Example inputs
How to interpret the result
Converting funds specifically up to the top of a chosen tax bracket, rather than converting a round dollar amount, is what actually keeps the conversion taxed at the intended rate. A round-number conversion that overshoots the bracket ceiling pushes part of that conversion into the next higher bracket without the filer necessarily realizing it happened.
Before you rely on it
What to check
Calculate room remaining in the target bracket specifically, rather than picking a round conversion amount and assuming it stays entirely within that bracket.
The common error
Where people go wrong with roth conversion bracket-fill calculator
Converting a round dollar amount without checking it against the specific bracket ceiling. Overshooting the ceiling pushes part of the conversion into the next higher bracket, taxed at a rate the filer may not have intended to pay on any part of it.
Sensitivity evidence
How estimated taxable income changes the available conversion room
| Estimated taxable income | Available conversion room | Estimated federal tax on room |
|---|---|---|
| $120,000 | $91,400 | $20,108 |
| $135,000 | $76,400 | $16,808 |
| $150,000worked example | $61,400 | $13,508 |
| $165,000 | $46,400 | $10,208 |
| $180,000 | $31,400 | $6,908 |
Every input, tested
Which input moves the available conversion room most
| Input | Tested from | To | Available conversion room at each end | Swing |
|---|---|---|---|---|
| Target bracket ceiling | $190,260 | $232,540 | $40,260 to $82,540 | $42,280 (69%) |
| Estimated taxable income | $135,000 | $165,000 | $76,400 to $46,400 | $30,000 (49%) |
| Marginal rate | 20.0% | 24.0% | $61,400 to $61,400 | none |
Two variables at once
Available conversion room by estimated taxable income and target bracket ceiling
| Estimated taxable income \ Target bracket ceiling | $169,120 | $211,400 | $253,680 |
|---|---|---|---|
| $120,000 | $49,120 | $91,400 | $133,680 |
| $135,000 | $34,120 | $76,400 | $118,680 |
| $150,000 | $19,120 | $61,400 | $103,680 |
| $165,000 | $4,120 | $46,400 | $88,680 |
| $180,000 | $0.00 | $31,400 | $73,680 |
Step by step
The worked example, input by input
| Input | Value used |
|---|---|
| Estimated taxable income | $150,000 |
| Target bracket ceiling | $211,400 |
| Marginal rate | 22.0% |
| Available conversion room | $61,400 |
| Estimated federal tax on room | $13,508 |
Where the inputs come from
Estimated taxable income is your projected taxable income for the year before the conversion, from a draft return or last year's return adjusted for changes. The target bracket ceiling is the top of the federal bracket you want to fill up to, and it depends on filing status and the tax year. The marginal rate is the rate charged in that bracket. Use figures from the current IRS tables, since brackets adjust yearly.
When the result stops applying
Filling a bracket does not account for the phase-in of other taxes: taxable Social Security, the 3.8% net investment income tax, Medicare surcharges and the loss of deductions and credits. State taxes add to the cost. Future tax law changes, including the scheduled expiry of some rates, can alter the outcome. The estimate is federal only.
What to compare it with
Use the Roth conversion calculator to test whether the tax paid pays off, and the IRMAA and taxable Social Security pages to check side effects. The RMD calculator shows what conversions reduce later. Many people convert a moderate amount each year rather than one large sum.
People also ask
Frequently asked questions
What is bracket filling?
It means converting or realizing just enough income each year to use up a low tax bracket, without spilling into the next higher one.
Which years work best for conversions?
Years with unusually low income, such as after retiring but before Social Security, RMDs or a pension begin, or a year with a big deduction.
Do I need to include state tax?
Yes, if your state taxes IRA income, since it adds to the total cost of the conversion. Some states exempt retirement income.