Are you Fat FIRE — and what's your number?

Fat FIRE is financial independence with no spending constraints — the top of the FIRE spectrum. It sits above Chubby FIRE: a budget built around the life you want rather than the life you can afford. In practice it means a household spending roughly $150,000 to $300,000+ a year, backed by a portfolio of about $5M and up.

The confusing part is that nobody agrees on the band. You'll find Fat defined as $150k+ of spending in one place and $250k+ in another; some call $200k+ "obese" or "super" FIRE, and net-worth targets range from $3.5M to $10M and beyond. That ambiguity is exactly why the calculator above leads with a clear answer: type your spending, and it resolves both questions at once — are you Fat, and what's your number?

FIRE isn't one finish line — it's a spectrum of how much you spend in retirement, and therefore how big a portfolio you need. Fat is the open top: the largest number, the longest to build, in exchange for a life with no budget ceiling.

Fat is the open-topped end — there's no upper limit, just how large a life you're funding. The step down, Fat vs Chubby, is below.

There's only one formula, and it's the same 25× rule behind every flavor of FIRE — your annual spending divided by a safe withdrawal rate:

To get the date, project what you have invested forward at your expected return, adding your annual contribution each year, until the balance reaches that number:

At a 3.5% withdrawal rate — this page's default, and the long-horizon convention for the decades-long retirement Fat usually implies — a Fat budget lands between $4.3M and $8.6M ($150k–$300k of spending × 28.6). Prefer the classic 4% rate? The same band eases to roughly $3.75M–$7.5M (× 25). The toggle on the calculator switches between the two live.

The number is open-topped. Unlike the other tiers, Fat has no ceiling — every extra $100k of annual spending adds $2.5M–$2.9M to the target. That's why "Fat FIRE" means so many different numbers to different people: it's defined by the life, not a round figure.

Single vs. couple. The number is driven by spending, not headcount — so a couple spending $200k together needs the same $5.71M as a solo spender at $200k. Couples often reach Fat sooner, because two high incomes build the portfolio quickly even at a luxury budget.

This is the comparison that actually keeps people up at night, because it's the one with real lifestyle stakes. Fat FIRE removes the last constraint: first-class everything, a second home, giving at scale — and a number to match, typically $5M and up. Chubby FIRE is a comfortable-but-considered life: nice travel, a paid-off house, no anxiety about a restaurant bill — but you still notice a $40k splurge, and the number is roughly half.

The gap is enormous in time, not just dollars. Moving your target spending from $120k to $200k roughly doubles the wait on the same savings — which is why many people who think they want Fat FIRE discover Chubby buys back the years that matter. Fat is worth it when the bigger life is genuinely the point, not when it's a number you're anchoring on out of caution.

It fits people who genuinely want an unconstrained retirement and have the income to fund it — high earners whose real life needs a big budget and who aren't willing to trade it down. If first-class travel, a second home, or giving at scale is the actual goal, Fat is the honest target, not an indulgence.

It's a weaker fit if you're reaching for Fat out of fear or anchoring when a Chubby budget would free you a decade sooner — the "one more year" trap is most expensive here, because the number is so large. Sequence-of-returns risk and pre-Medicare healthcare still apply, though Fat carries the most margin to absorb them; the real risk is letting a number you don't need keep you working.