Roth conversion calculator
See what a conversion actually costs, bracket by bracket, how much more you could convert before the next rate kicks in, and whether it beats leaving the money where it is.
On $120,000 of income, converting $100,000 costs about $29,134, an effective 29.1% even though the conversion reaches the 32% bracket. About $1,800 of room is left in your current bracket.
Wages and anything else ordinary
What you expect to pay on withdrawals
An effective 29.1% on $100,000, even though the conversion reaches the 32% bracket. It is taxed bracket by bracket, not at one rate.
Before the next dollar costs 24%
Stacked on $103,900 of taxable income
At a flat 5%
Tax-free from here on
Taxed at 22% on withdrawal, plus the side fund
| Bracket | Converted at this rate | Federal tax |
|---|---|---|
| 22% | $1,800 | $396 |
| 24% | $96,075 | $23,058 |
| 32% | $2,125 | $680 |
Converting is behind by $15,533 on these assumptions. Paying from savings is credited fairly: the money you would have spent on tax is given to the other side as an invested side fund, taxed on its gain. This conversion also pushes your income across the net investment income tax threshold, which can pull investment income into an extra 3.8%. That is flagged here, not costed.
Estimates only, not tax advice. Uses the 2026 federal schedule and a flat state rate. Excludes the 5-year rule on converted amounts, required minimum distributions, pro-rata basis in an IRA holding after-tax contributions, and state tax at withdrawal. Net investment income tax and IRMAA surcharges are flagged where relevant but not costed.
The effective rate climbs as the conversion grows
| Converted | Federal tax | Effective rate | Top bracket reached |
|---|---|---|---|
| $25,000 | $5,964 | 23.9% | 24% |
| $50,000 | $11,964 | 23.9% | 24% |
| $100,000 | $24,134 | 24.1% | 32% |
| $200,000 | $57,564 | 28.8% | 35% |
| $400,000 | $127,564 | 31.9% | 35% |
Single filer with $120,000 of other income, 2026 federal schedule, no state tax. Note the effective rate is always below the top bracket reached, which is exactly what a flat-rate estimate misses.
Why one marginal rate is the wrong answer
A conversion is not taxed at your bracket. It is stacked on top of your other income and taxed in slices, so the first part may fall in the band you are already in and the rest spills upward. The cost is the difference between your tax with the conversion and without it, which is what this calculator computes, and it always comes out below the top rate the conversion reaches.
That is why bracket headroom is the useful number. Converting exactly up to the top of your current band costs one known rate; a dollar more starts paying the next one. Spreading conversions across several years to stay inside a band is the whole strategy, and it only works if you can see where the line is.
The comparison at the end is deliberately fair. Paying the tax from outside savings is usually the better move, but the cash is real, and it would otherwise have stayed invested. So the leave-it-alone side gets credited with a side fund holding that same money. If you cannot contribute to a Roth directly because of income limits, the Roth IRA calculator shows where those limits fall, or see the whole picture in the retirement calculator , or book a free consultation .