Roth Conversion Toolkit is an MIT licensed TypeScript library and embeddable widget that prices a Roth IRA conversion the way the tax code actually works, not the way flat bracket calculators pretend it does. A converted dollar is taxed at its bracket rate, and then three more meters run. It can drag another 85 cents of Social Security benefits into taxable income, it can claw back 6 cents of the temporary senior deduction that exists only through 2028, and it can push income over a Medicare...