Money Archives - Kind of Lost

How Full Should You Fill Your Tax Bracket? I Ran the Numbers

“Fill up your tax bracket” skips the hard part: which bracket. I ran my Roth conversion optimizer 34 times to see where it stops, and why a big IRA should fill more than feels comfortable.

“Fill up your tax bracket” is the most common Roth conversion advice there is, and it skips the only part that’s hard: which bracket? The 12%? The 22%? Halfway into the 24% because it’s only two points more? I got tired of the hand-waving, so I ran my own Roth conversion optimizer 34 times, changing one thing at a time, and watched where it stopped.

Short version: it almost always stops exactly at a bracket edge, never somewhere in the middle. Which edge depends on a single comparison, and that comparison isn’t the one most people make.

Chart: total Roth conversions by assumed future tax rate. With a $1.2M IRA it is flat at about $196k up to 20%, then jumps to $565k at 23% and above. With a $3M IRA it rises steadily and converts the whole IRA from 25% up. — Same retiree, same accounts, only the future tax rate changes. The small IRA doesn’t slide gradually, it jumps from one bracket edge to the next.

Roth Conversion vs ACA Subsidy: The Cliff Is Back

Two dollars of income cost a couple I was modeling last week $9,574. Not two thousand — two. That is the Roth conversion vs ACA subsidy problem in one line, and as of January it is live again for anyone retiring before 65.

The enhanced premium tax credits that ran from 2021 through 2025 expired on December 31 and were not extended. What came back with them is the old 400%-of-the-federal-poverty-line cliff: below it you get a subsidy, above it you get nothing at all. Not a taper. Nothing.

Chart of the 2026 ACA subsidy cliff: household premium rises gently with income, then jumps from $8,426 to $18,000 at $84,600 of MAGI — What a married couple pays for a benchmark silver plan as income rises. At 400% of the federal poverty line the premium tax credit disappears all at once — which is why a Roth conversion in a pre-Medicare year needs to be sized, not guessed.

Safe Withdrawal Rate by Age: Why 4% Isn’t One Number

The “4% rule” gets repeated like it’s one universal number, but the safe withdrawal rate by age isn’t actually flat — it moves depending on how long your money needs to last, which is another way of saying it depends heavily on your age when you start withdrawing. I built my own withdrawal calculator specifically because a flat percentage didn’t fit an early-retirement timeline, and the more I dug into the math, the more the “4%” felt like a rounding of something that should really be a curve.

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How to Retire Early: The Math That Actually Matters

People ask me how to retire early like there’s a secret I’m withholding — some clever investment, a trick with real estate, a system nobody else knows about. There isn’t. I retired early, I still don’t have a boss more than a decade later, and the math behind it is boring enough to explain in two paragraphs. The hard part was never the math. Here’s the version I wish someone had handed me plainly, instead of making me piece it together from forum threads.

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A Withdrawal Rate Calculator That Draws Down to Zero

After I put the Roth conversion tool online, the question I kept getting wasn’t about conversions at all. It was simpler and scarier: “OK, but how much can I actually spend?” Almost every withdrawal rate calculator answers that by multiplying your savings by 4% and calling it a day. So I added a mode to my own optimizer that throws the flat percentage out and solves for the real number — the most you can spend every year while drawing every account down to zero by the end of the plan.