Five pieces, ordered so you can start anywhere and still follow the argument. Everything here describes how Roth conversions work — none of it is tax advice.
Start here What a conversion is, and why the obvious way to price one is wrong.
Going deeper The two effects that put the biggest gap between your bracket and your real cost.
Advanced Where the case for converting early gets its strength.
The widow's penalty 8 min The survivor files single on much the same portfolio — half the brackets, half the thresholds.
When you want to put numbers to any of it, the calculator is the point of the whole site.
What this is. A planning model built on 2026 federal tax law — the brackets and standard
deduction from IRS Rev. Proc. 2025-32, the OBBBA senior deduction, Social Security taxability under
Pub. 915, long-term capital gain stacking, the 3.8% net investment income tax, 2026 Medicare IRMAA
tiers from the CMS premium announcement, and SECURE 2.0 required minimum distribution ages.
The optional refinements add the ACA premium tax credit and its restored 400%-of-poverty cliff
(applicable percentages from Rev. Proc. 2025-25, 2025 HHS poverty guidelines), the Form 8606 pro-rata
rule for after-tax IRA basis, qualified charitable distributions at the 2026 $111,000 limit, the
survivor's switch to single filing, and capital gains realised to fund the tax.
What it is not. It is not tax advice, and I am not a tax advisor or a financial advisor.
It simplifies real things: state tax is a single flat rate rather than a real bracket schedule, and it
assumes today's law persists. Returns are a single smooth rate applied to every account, so nothing
here captures volatility or the order in which good and bad years arrive — converting into a market
trough is far better than the average suggests, and converting at a peak far worse. The taxable
account's own dividends and turnover aren't taxed each year either, which quietly flatters the
do-nothing case, since that is the path that ends with the larger taxable account.
IRMAA and ACA thresholds two or more years out are estimates — the real ones aren't published yet, so
leave margin. It also does not model the alternative minimum tax, the 5-year clocks on converted
principal, state-specific credits, or Medicaid eligibility below 138% of poverty. Before you actually
convert, run your numbers past a CPA or a fee-only advisor, and remember that a conversion is
irreversible: recharacterization was eliminated in 2018.