Model Roth conversions, IRMAA thresholds, Monte Carlo outcomes, and estate strategy — with the depth of a professional tool and the privacy of software you actually own. Start free in the web app, including a federal retirement sample for FERS-style planning. $149 unlocks the full planner and desktop app. No subscriptions. No cloud.
No sign-up required. Start with sample data, your own numbers, or the federal sample path.
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.
Not sure yet? Run a real retirement projection in 60 seconds. Enter your savings, Social Security, and spending — get a year-by-year forecast with Monte Carlo simulation. No sign-up. No install. Nothing to download. Federal visitors can also start with a FERS-style sample plan.
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 server, your data never leaves your machine. 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. Your data is always yours.
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.
Most retirement software sends your income, assets, and account details to a cloud server. That data is used for analytics, shared with marketing partners, and potentially used to train AI models.
Fatboy is built differently. The desktop app runs entirely on your machine — no account creation, no data harvesting. The web app runs Python locally in your browser via Pyodide — your calculations never touch a server.
Pro users can optionally sync an encrypted backup across devices. Your plan is encrypted in your browser before it leaves — using your license key as the encryption key. We receive ciphertext we cannot read. Your retirement plan is nobody else's business.
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 to compare strategies, save scenarios, export reports, and keep using the tool for years.
Start free in the web app, move to the full planner when you want deeper control, or lock in Founding Member pricing at $149 before the price rises to $249 at 200 users.
Free preview first. Full planner and desktop access when you are ready for saved scenarios, exports, and deeper analysis.