or-tools-series-roth Archives

Building a Roth Conversion Optimizer: Lessons Learned

This is the third model I’ve pulled out of a spreadsheet and rebuilt as a web app, after the staff scheduler and the vehicle router. Going in, I assumed the optimization would be the hard part. It wasn’t. The solver finished in under a second every single time. The hard part was trusting what it told me — and the lessons that came out of that are the ones I keep coming back to.

Here’s what building a Roth conversion optimizer actually taught me. Not about Roth conversions — that’s a separate post — but about the craft of turning a twenty-year-old model into something other people can trust.

Roth conversion optimizer web app interface

Free Roth Conversion Software (It’s Live)

A while back I wrote here that I was turning my Excel model into free Roth conversion software — and that post promised “coming soon.” It’s no longer coming; it’s live and free to use. No signup, no download, no spreadsheet skills required: enter your numbers in the browser, click optimize, and a real solver plans your conversion schedule year by year.

The Roth Conversion Math: A Linear Program

This is the “show your work” post in the series. If you came for the FIRE strategy you can happily skip it; if you want the Roth conversion optimization written out as an actual linear program — decision variables, constraints, objective — this is for you. It mirrors the Excel + OpenSolver model I described in part 2.

How Much Should I Convert to a Roth Each Year?

This post is about a question I keep circling back to as an early retiree: how much to convert to a Roth in any given year. Not whether to convert — I’m already sold on that — but the actual dollar amount, year by year. It turns out to be a surprisingly good little optimization problem, and this is how I think about it.

Hand-drawn sketch of the IRA to Roth conversion trade-off, tax versus time — This is how it started — the sketch in my notebook, long before any spreadsheet.

The Roth Conversion Ladder (and Its Blind Spot)

If you retire before 59½ with most of your money locked in a traditional IRA or 401(k), you run into an awkward problem: the money is there, but reaching it normally means a 10% early-withdrawal penalty on top of income tax. The Roth conversion ladder is the classic FIRE workaround, and it is the setup for everything else I want to write about in this series.