Fat FIRE targets a higher expense level and a correspondingly larger portfolio. Many Fat FIRE planners use a more conservative withdrawal rate (3.5% instead of 4%) for longer horizons.
FIRE number
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Coast FIRE number
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Years to FIRE
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Age at FIRE
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Year-by-year projection
| Year | Age | Portfolio |
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What the word "fat" actually adds to FIRE
Standard FIRE answers a spartan question: what is the smallest portfolio that lets me stop working. Fat FIRE asks a different one. It targets a comfortable, even luxurious, lifestyle in retirement, typically defined by spending of $100,000 or more per household per year. That means travel, premium healthcare, private school or college for kids, and living in a high cost city without trimming your life to fit a budget. The arithmetic is the same as ordinary FIRE; the inputs are simply larger and the safety margin tends to be wider.
This calculator builds your FIRE number by dividing annual expenses by a safe withdrawal rate, then projects how many years of saving and compounding it takes to get there. It also reports a Coast FIRE figure, the amount that, once reached, can grow to your full target with no further contributions before your retirement age.
Building a $4.3 million target on cautious assumptions
The default scenario describes a high earner: a 32 year old spending $150,000 a year, holding $300,000 today, saving $75,000 a year, expecting a 5% real return, and using a conservative 3.5% withdrawal rate with a retirement target of 50. Watch how the FIRE number and the timeline come out.
| Quantity | Result |
|---|---|
| FIRE number ($150,000 divided by 3.5%) | $4,285,714 |
| Expense multiple (1 divided by 3.5%) | about 29 times |
| Years of saving to reach it | 24 years |
| Age when the target is hit | 56 |
| Coast FIRE number today (target at age 50) | $1,780,803 |
Two honest lessons fall out of this. First, $4.3 million is a serious number, and even on a $75,000 annual savings rate it takes 24 years to build, landing at age 56 rather than the hoped for 50. Fat FIRE at a young age usually requires either a much higher savings rate or a business exit. Second, the Coast FIRE figure of roughly $1.78 million shows the power of front loading: reach that balance and compounding alone carries you to the full target by 50, even if you never save another dollar.
Watching the portfolio climb to target
The projection compounds year by year. Because growth is multiplicative, the curve is gentle early and steep late. The chart traces the balance at five year marks on the way to the $4.29 million goal line.
Why Fat FIRE leans on 3.5% instead of 4%
The familiar 4% rule comes from the Trinity Study, which tested a 30 year retirement. Fat FIRE retirees often quit in their 40s or early 50s, facing 40 or even 50 years of withdrawals. Over that longer horizon, a 4% rate carries more sequence of returns risk, the danger that a bad market early in retirement permanently damages the portfolio. Dropping to 3.5% lifts the required multiple from 25 times expenses to about 29 times, and a 3% rate pushes it to 33 times. The larger cushion also leaves more room to absorb the lumpier, less predictable spending that a Fat FIRE lifestyle tends to involve, from major travel to helping adult children.
Who this is built for, and one quiet assumption
This tool fits high income professionals in tech, finance, law, or medicine, and founders modeling life after a liquidity event. If you spend well into six figures and refuse to downsize in retirement, this is your version of the FIRE math. A subtle point worth knowing: the engine adds your annual savings first and then applies the year's growth, so the first year's contribution earns a full year of return. That is a reasonable convention, but it makes the result slightly optimistic compared with contributing at year end, and it can shift the years to FIRE by one. The bigger caveat is that the calculator works in real, after inflation returns and pretax dollars. It does not model the substantial tax drag a Fat FIRE retiree faces, since drawing $150,000 a year from taxable and traditional accounts creates a real tax bill. Build a margin for taxes on top of the number this produces.
How is Fat FIRE different from regular FIRE and Lean FIRE?
It is the same formula at three spending levels. Lean FIRE targets a frugal lifestyle, often under $40,000 a year and a portfolio near $1 million. Regular FIRE sits in the middle. Fat FIRE aims at $100,000 or more in annual spending and a portfolio of $2.5 million and up, with many adherents targeting $4 million or more once a conservative withdrawal rate is applied.
Should I use a nominal or real return in this tool?
Use a real, after inflation return, which is why the default is 5% rather than 8%. Because the calculator keeps everything in today's dollars, entering a nominal return would overstate your future purchasing power. A 5% real return roughly corresponds to an 8% nominal return with 3% inflation.