Yes, you are correct that for calculating additional income tax amounts, you will want to use the marginal rate to get an estimate of the anticipated amount of tax you will owe. The higher tax brackets cover a very wide range as can be seen on the following link - IRS Tax Bracket 2025 . Unless you are making a very large conversion, it's likely that the conversion will fall completely into one of these brackets.. These brackets will get inflation adjusted for 2026, but also keep in mind that the tax code is written in pencil, so tax law changes can also affect the amount of tax on the conversion.
