A few years ago I sat down with a financial adviser in the US and asked a straightforward question: when can I afford to retire?
He was good at his job. He understood 401(k)s, IRAs, Social Security. Then I mentioned I also have a UK State Pension entitlement, a SIPP, and an ISA from before I moved to the States. He was honest about it: that wasn't something he could model.
Fair enough. Most advisers are licensed in one country. That's how the system works. But it left me with a problem. I had retirement savings split across two countries, two currencies, two tax systems, and two state pension schemes — and no tool that could put them all in one place.
So I went looking for one. I tried every retirement calculator I could find. They all assumed one country. One currency. One pension. That's fine if your entire financial life fits inside a single border. Mine doesn't. If you're reading this, yours probably doesn't either.
What I built
RetireFlexi started as a spreadsheet for myself. Then a better spreadsheet. Then a spreadsheet with so many tabs that I started rebuilding it as a proper application.
I shared it with a few friends — other expats in the same situation. They found it useful and started asking me to add things. Australian superannuation. Canadian RRSPs. Monte Carlo simulations. Rental property modelling. It kept growing.
Today it covers 49 countries, handles any combination of accounts and pensions, converts everything to a single reporting currency using live exchange rates, and stress-tests your plan against 5,000 randomised market scenarios. It does the thing I couldn't find anywhere else: it puts the whole picture in one place.
I also started writing about the problems I ran into along the way. If you're dealing with US Social Security and a UK State Pension at the same time, I wrote up how the two systems actually interact. There's also a guide to the tax side of expat retirement planning a practical look at the best countries for expat retirement in 2026, and a deep dive into retiring in Portugal with the actual tax numbers.
Why your data never leaves your browser
I wouldn't type my 401(k) balance into a random website. So I built RetireFlexi to never ask for that trust.
Everything runs in your browser. Your account balances, pension values, income figures — none of it is sent to a server. There is no database of retirement plans. No account to create. Nothing to breach. No data is stored on our servers. Ever.
The save question took some thinking. One friend was using RetireFlexi on an iPad. Another on a Chromebook. Neither works in technology — they just wanted to check their numbers and come back to them later. Devices like those don't handle long-term storage of ad-hoc files all that well, and asking non-technical people to manage JSON exports felt like a bad answer. So I built save-to-email: your plan is delivered as an attachment straight to your own inbox. You keep it in your email, open it whenever you want, and I handle the delivery — but I never see, store, or have access to what's inside.
Why it's free
Because it started as something I needed for myself. I never set out to build a product — I set out to answer a question about my own retirement. When other people found it useful, charging for it felt wrong. The running costs are low, and I'd rather more people have access to decent multi-country retirement projections than gate them behind a subscription.
What this is not
I work in software and technology product management, so I know how to build things — but I'm not a financial adviser. RetireFlexi is a calculator — it runs the numbers you give it through the logic you configure. It doesn't tell you what to invest in, when to retire, or where to move. Those decisions are yours. The tool just makes them easier to think about with real numbers in front of you.
If you need personalised financial advice, especially on cross-border tax, find an adviser who specialises in expat finance. There aren't many, but they exist. RetireFlexi can help you arrive at that conversation with better questions.