Fat FIRE: independence with the lifestyle intact.
Fat FIRE doesn't change the arithmetic — it raises the spending. A bigger annual budget means a bigger portfolio and a longer runway, in exchange for a retirement that gives nothing up.
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Sample result
PreviewThis household's Fat FIRE number
$3,750,000
Funds $150,000 a year at a 4% withdrawal rate
Reached at
Age 61
Years away
29 years
Coast Fat number
$1.1M
Coasting by
Age 53
That's 2× this household's $1,875,000 target number, and arrives about 11 years later — the price of the bigger lifestyle, and nothing else.
The sample's assumptions
- Age 32, retiring at 65
- $220,000 invested today
- $175,000 take-home pay
- Saving 35% of it ($5,104/mo)
- $75,000/yr target retirement spending
- 4% safe withdrawal rate
- 7% return, 3% inflation
Run it with your own numbers
Create a free account to enter your own spending, edit every tier, and watch all four numbers update — saved across devices.
It isn't a different formula. It's a different lifestyle.
Every tier of FIRE runs the same arithmetic: the money you expect to spend in a year, divided by your safe withdrawal rate. Change the spending and you change the number — that's the whole difference between Fat FIRE and every other flavour.
$150,000 ÷ 4% = $3,750,000
Fat FIRE spending ÷ safe withdrawal rate = the portfolio that funds it indefinitely.
Lean FIRE
$1.3M
funds $52,500/yr
Coast number today $373.3K
Your target
$1.9M
funds $75,000/yr
Coast number today $533.3K
Fat FIRE
$3.8M
funds $150,000/yr
Coast number today $1.1M
Every number here comes from the same household above — only the spending figure changes.
What counts as fat?
Whatever 'no compromises' costs you — travel, a bigger home, private school, generosity, a cushion for the unexpected. ProsperMap starts the fat tier at twice the retirement spending you entered, because comfort is relative to your own life, and the figure is fully editable.
Coast Fat, explained
Every tier has a coast number: the amount that, left completely alone, grows into that tier's FI number by your target retirement age. The fat tier's coast number is what the community calls Coast Fat — cross it and the comfortable retirement is already funded, even if you never invest another dollar.
Explore the other flavours
Same calculator, same formula — a different spending figure each time.
Frequently asked questions
See your own fat number.
Create a free account to run every FIRE tier — including Coast Fat — on your real numbers, then learn the system behind them in Build Real Wealth.