Answer a few questions and get a fast first read on whether your plan works, where it gets tight, and whether your retirement date still holds up. Answer a few questions and get a fast first read on whether your plan still works.
No signup. No install. Works on phone or desktop. Many planning tools are built around accounts, subscriptions, and cloud storage first. Fatboy is built around control first: quick answer now, guided planner next, and desktop plus optional encrypted sync when you want more depth.
No signup | No install | Opens instantly
Want saved scenarios, exports, or deeper analysis after the quick answer? See what Desktop Pro adds.
Founding Member price | Increases to $249 at 200 users
Price increases to $249 after 200 Founding Members
Founding Member spots
Founding Member pricing
Best for people who want to compare strategies, save scenarios, export reports, and revisit decisions over time.
One-time purchase. Direct support. No subscription lock-in.
Most people do not need the full build right away. Start with the quick answer, then move into the guided planner or desktop version when the result is worth pressure-testing.
Use the quick web experience when you want to know whether the plan basically works before you invest more time.
Use the guided planner or Desktop Pro when you want more comparison depth, saved scenarios, exports, and a tool you keep coming back to.
Use a few key numbers to get a fast read on whether your retirement plan works. If the answer is close, shaky, or worth exploring, continue into the guided planner with your numbers carried forward.
The free trial gives you a real taste. The Pro license unlocks everything - on your desktop and in your browser.
Limited trial | No account required
Runs entirely in your browser via Pyodide - Python in the browser, no planning server receiving your numbers by default, and a local-first workflow from the start. Try the full interface with limited scenarios before you buy.
Founding Member | Price increases to $249 at 200 users
One license key unlocks the Windows desktop app, the Linux AppImage, and the full web app. Use whichever fits the moment. Local-first by default, with optional encrypted cloud sync when you want it.
Price increases to $249 after 200 Founding Members
Already purchased? Download: Windows | Linux AppImage
When OBBBA passed in July 2025, most retirement tools went stale. Fatboy users updated their tax parameters in 10 minutes and kept planning.
Edit federal and state tax brackets yourself. Model TCJA expiration, OBBBA senior deductions, capital gains rate changes - without waiting 6 months for a vendor update.
See exactly how a $50k Roth conversion impacts your taxes this year, your IRMAA brackets at 65, and your RMDs at 75. Year-by-year, full tax effects.
From optimistic GBM baseline to conservative regime switching to a full century of historical data. A plan that holds up across all seven is a plan you can retire on.
Find exactly where your plan starts to fail. Minimum required returns. Maximum safe withdrawal rate. Color-coded risk zones so you know what margin you actually have.
Year-by-year estate projections, legacy goal tracking, inherited IRA RMD implications under the SECURE Act 10-year rule, and estate tax exposure against TCJA exemption thresholds.
Export polished, client-ready summaries of your analysis. Useful for reviewing with a spouse, sharing with a CPA, or documenting your strategy for annual review.
1% AUM on $1M is $10,000 a year. Boldin is $12/month. ProjectionLab is $109/year. Fatboy is $149 once - desktop app, web app, all future updates. By year two you've paid less than one month of a competing subscription.
Federal retirement is not just a pension input. Fatboy models how federal-style income sources start, stop, and interact inside the full retirement plan year by year.
See pension, supplement, TSP, and Social Security work together year by year instead of flattening everything into one generic income line.
Fatboy is planning depth, not hand-holding. The people who get the most from it know what they want to model.
Many planning tools are built around accounts, subscriptions, and cloud storage first. That means your retirement workflow begins by handing over your financial details to somebody else's system.
Fatboy is built around control first. The desktop app runs on your machine with a local-first workflow. The web app runs Python locally in your browser via Pyodide, so your calculations do not depend on a planning server.
If you want cross-device access later, Pro users can optionally sync an encrypted backup. Your plan is encrypted in your browser before upload using your license key, and we receive ciphertext we cannot read.
The Windows and Linux apps run entirely on your machine. No internet required for planning. Data lives only on your computer.
The web app runs Python locally in your browser - not on a server. Your numbers stay on your device by default. No account required for the trial.
The only automatic server call is license key validation. Pro users can optionally sync plans across devices - but the data is encrypted in your browser before upload, using a key only you hold. We store ciphertext we cannot read. How it works ->
We don't sell data, run analytics on your plans, or share anything with third parties. There's no business model that requires it.
Built for serious DIY planners who want a fast first answer now and a deeper tool ready when the decision gets more serious.
Get the quick answer first. If the result makes you pause, continue in the guided planner or lock in Founding Member pricing for the full desktop and web version.
Quick answer first. Guided planner next. Desktop Pro when you want saved scenarios, exports, and deeper ongoing analysis.