I spent an evening trying to plan our retirement, and every calculator I opened broke on the same question: what happens in the years between when I stop working and when my partner does?
Not a complex question. Two people, two exit dates, one household. And yet every tool I found had a single retirement date field. One slider. As if couples always quit on the same Tuesday.
That was the moment I stopped looking for a tool and started building one. But the more I built, the more gaps appeared. What about the year I want to take off at 36 before officially retiring? What about our son's university costs landing at a specific age? What about the fact that a big chunk of our portfolio is generating active income through options strategies, not sitting in index funds? None of the tools I tried could express any of this cleanly. So I kept going.
This is an account of what I built, what the existing tools look like, and where I think the whole category is still falling short.
What the market looks like
The FIRE calculator space is more crowded than most people realise, and more limited.
| Tool | Strengths | Limitations |
|---|---|---|
| FIRECalc / cFIREsim | Historical backtesting to 1871, solid Monte Carlo | Interface largely unchanged in years, U.S.-only, single retirement date |
| ProjectionLab | Modern UX, scenario lanes, Sankey diagrams | Around $6/month as of writing, U.S. tax focus, no true multi-spouse planning |
| IncomeTree / Meet Warren | Country-specific (Canada, UK) account support | Single-country, no active income modelling |
| Engaging Data / WalletBurst | Free, accessible | Single retirement age, household treated as one entity |
Almost every tool assumes you are American, assumes your portfolio is 100% passive, and treats the household as one entity with one retirement date. ProjectionLab comes closest to handling couples correctly — you can set separate retirement ages and assign accounts per person. But its own community has a long-open feature request called "Family account" asking for two spouses to share a plan without sharing login credentials. The most common workaround people suggest is giving your partner your password.
What none of them handle cleanly is what I will call the interstitial phase: the years between when one person stops working and the other does. What is the safe withdrawal rate when only one salary disappears? What does the household expense structure look like when one person is no longer commuting but the other still is? The math is not complicated. It just requires someone to model it.
What I ended up building
The tool is a single-page React app. No backend, no account, no server. Everything runs in the browser.
The feature that drove the whole thing is per-person retirement tracking. Each person gets their own current age and their own planned exit age. The projection loop runs year by year, tracking which person is working, which has retired, and what the household looks like at each phase, including the interstitial years in between. The gaps the opening tools missed are explicitly modelled, not averaged away.
From there, two more features emerged that I have not seen elsewhere:
The first is sabbatical years. You can mark specific ages as non-earning for either person, and the model treats those years differently from full retirement: no salary, but no portfolio drawdown assumption either. This came from a real conversation in our household about wanting a year off at 36 before either of us had officially retired. No tool I found had a way to express it.
The second is active income as a first-class input. Most FIRE tools assume you put everything in index funds and stop working entirely at a fixed date. This one separates an active portfolio (options income, covered calls, the Wheel strategy) from a passive index portfolio. You set a gross yield, apply your capital gains tax rate, and the model handles reinvestment during accumulation and drawdown during retirement differently. The question this unlocks is: at what portfolio size can I stop actively trading and just let passive growth carry me to FIRE? That crossover point is what the tool calls Coast FIRE, and it is calculated automatically.
It also handles life events landing at specific ages (our son's university, a future wedding, an inheritance we might receive), and real tax brackets for six jurisdictions: Canada (BC and Ontario), the U.S. (California and Texas), the U.K., Australia, and India. For India specifically: the new tax regime brackets, LTCG at 12.5%, and cess. Switching jurisdictions updates the inflation and cash rate assumptions automatically, because the difference between 2.5% Canadian inflation and 3% Australian inflation compounds meaningfully over 30 years.
One last thing, because a few people have asked: the visual theme. The parchment colour palette and serif typography are meant to look like an Age of Empires resource screen, the place where you watched your gold and wood tick upward while planning your next campaign. It is an easter egg, not a design principle. But making a financial planning tool feel like a strategy game turned out to make it more enjoyable to use, and tools you enjoy using are tools you actually update.
What is still missing
The biggest gap is visual rather than computational. The projection loop models the interstitial phase correctly, but the chart does not isolate it. There is no view that says "here is what your household looks like in the 24 months between your exit and your partner's." You can see it in the data table, but not in a dedicated chart. That is the next thing worth building.
The projection is also deterministic. You set return assumptions and it projects them forward. What it does not show is the spread of outcomes across different market sequences. Two households with identical inputs but different market timing in their first five years of retirement can end up in very different places. The tool is honest about being a structured estimate rather than a probability distribution, but that is a real limitation for anyone who wants to stress-test a plan.
And the tax brackets will go stale. Canada will adjust its brackets. India will revise the cess structure. Those numbers will need updating when laws change. That is a maintenance burden I went in knowing about.
Why bother
Let me come back to where this started.
I opened a FIRE calculator to plan our retirement. It had one retirement date field. I tried the next one. Same. Six more, same result. All of them treated the household as a single entity with one salary and one exit date.
What I wanted was to model two people who are different ages, want to retire at different ages, plan to take sabbaticals at different points, and run a portfolio that is not purely passive. Every tool asked me to simplify away at least one of those things.
So I built one that does not ask that. It is a structured napkin calculation, not a replacement for a financial advisor. But it handles the couple-with-different-ages scenario correctly, it knows what a covered call is, and it does not require an account to use or share.
That is the whole reason.
The tool is live at FIRE Planner. No account, no email, no subscription.