How "Fill the Bracket" Conversions Work
A Roth conversion moves money from a traditional IRA or 401(k) into a Roth IRA. The converted amount is added to your taxable income for the year and taxed at your ordinary income rates — but future growth and withdrawals from the Roth account are tax-free. The "fill the bracket" strategy means converting just enough to use up the remaining room in your current tax bracket without pushing any income into the next, higher bracket.
2026 Federal Income Tax Brackets
The table below shows the 2026 brackets used by this calculator (Source: IRS Revenue Procedure 2025-32, via Tax Foundation).
| Rate | Single | Married Filing Jointly | Head of Household |
|---|---|---|---|
| 10% | $0 – $12,400 | $0 – $24,800 | $0 – $17,700 |
| 12% | $12,401 – $50,400 | $24,801 – $100,800 | $17,701 – $67,450 |
| 22% | $50,401 – $105,700 | $100,801 – $211,400 | $67,451 – $105,700 |
| 24% | $105,701 – $201,775 | $211,401 – $403,550 | $105,701 – $201,775 |
| 32% | $201,776 – $256,225 | $403,551 – $512,450 | $201,776 – $256,200 |
| 35% | $256,226 – $640,600 | $512,451 – $768,700 | $256,201 – $640,600 |
| 37% | $640,601+ | $768,701+ | $640,601+ |
Why Convert Now Instead of Later?
Traditional retirement accounts are taxed when you withdraw, and Required Minimum Distributions (RMDs) eventually force withdrawals whether you need the income or not. Converting in years when your taxable income is unusually low — between jobs, early retirement before Social Security and RMDs begin, or any year with lower-than-usual income — lets you pay tax on that money at a lower rate than you might face later. It also reduces the size of future RMDs and can leave heirs a tax-free inheritance.
State Taxes on Conversions
Most states that tax income treat a Roth conversion as ordinary income, the same as the IRS does. A few states have no income tax at all, in which case you can set the state rate to 0%. If you're considering relocating to a no-tax state in retirement, converting before or after a move can change your total tax bill significantly — that timing decision is outside the scope of this calculator but worth discussing with a tax professional.
Reading Your Results
The recommended conversion amount is the smaller of two numbers: how much room remains in your selected bracket, and how much you actually have available in traditional accounts. The tax shown is calculated using the full progressive bracket structure — if your current income is below the target bracket, part of the conversion may be taxed at lower rates on its way up to the target ceiling, which is why the effective rate on the conversion is often below the target bracket's rate.