FIRE Archives - Kind of Lost

Retirement Withdrawal Tax Calculator: Your Real Rate

“How much tax will I pay if I take $30,000 out of my IRA?” sounds like it should have a one-line answer. It doesn’t. The withdrawal stacks on top of your other income, it can drag your Social Security into tax with it, and before 59½ there’s a penalty on top. I built a retirement withdrawal tax calculator to do that arithmetic properly for one year, and to show the number most people never see: what the next dollar costs.

It’s free, no signup, and it uses the 2026 federal brackets. I’m 58, single, retired early, and planning my own drawdown, so I use it too.

Retirement withdrawal tax calculator showing $3,226 of federal tax on a $30,000 IRA withdrawal for a single filer with Social Security, a 12% bracket and $222 of tax on the next $1,000 — The example below: a 12% bracket, a 10.8% average rate, and $222 of tax on the next $1,000.

IRMAA Calculator: What One Dollar Over the Line Costs

I’m 58, single, and Medicare is still seven years away. It already matters to me, though, because of one rule: the premium I’ll pay at 65 is set by the income on the tax return I file for the year I turn 63. Those are exactly the years I’d want to do Roth conversions. So I built a small IRMAA calculator that answers the narrow question first: given a year’s income, which Medicare surcharge tier does it land in, what does that cost, and how close is the next cliff?

It’s free, there’s no signup, and it runs in your browser. You enter three things and it answers right away.

IRMAA calculator showing a single filer with $140,000 of MAGI in tier 2 of 5: $2,885 a year extra, $240.40 a month, $31,000 of room before the next step — The example below: a single filer with $140,000 of MAGI lands in tier 2 of 5.

A Roth vs Traditional 401k Calculator for Your Whole Career

I built a Roth conversion optimizer because retirement is the phase I’m in. That sounds reasonable until you notice what it leaves out: by the time anyone needs a conversion plan, the big decision (traditional or Roth, every paycheck, for decades) has already been made. So I built the piece I was missing: a Roth vs traditional 401k calculator that optimizes the working years and the retirement years together, as one plan.

It’s free and needs no signup. You enter your salary, when you plan to stop working, what you spend, which accounts you have, and how your employer matches. It tells you how much to put in each account this year, and every year after that.

Roth vs traditional 401k calculator results: this year's split between Roth 401(k) and Roth IRA, and the optimal mix compared with always-traditional and always-Roth — The sample plan: this year’s split, and what the optimal mix is worth against the two defaults.

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.