The original FIRE math is one number. Take your annual spending, multiply by twenty-five, save that, retire. Done. The problem is that most people who run that equation get a result they cannot reach in any reasonable horizon, so they conclude FIRE is for software engineers in San Francisco with stock grants and no children. The variants exist because the original math was load-bearing for a person who probably wasn’t you.
Five variants are worth knowing. Each one solves a real problem the pure 25× number ignores. None of them are aspirational labels for a forum bio. They are different shapes of exit.
Pure FIRE
The classic. Annual spending × 25, hold in a 60/40 portfolio, withdraw 4% adjusted for inflation, retire forever.
Worked example: Marco, 38, spends $55,000 a year in Denver. His pure FIRE number is $55,000 × 25 = $1,375,000.
At a savings rate of $40,000/yr and a 6% real return, he hits it around age 53. That’s fifteen years of grinding from where he stands. Most people, reading that sentence, quietly close the tab.
Pure FIRE assumes you’ll live to roughly 95 and want the portfolio to survive. It is calibrated for the longest plausible retirement. If your honest horizon is shorter, you are over-saving by a factor that buys you years of the wrong life.
Lean FIRE
Same math, lower threshold. Annual spending of $20,000–$30,000, so the number lands between $500,000 and $750,000.
Worked example: Priya, 35, has stripped her life to $24,000/yr — small apartment in Pittsburgh, one used car, cooks at home, no streaming bloat. Her lean FIRE number is $24,000 × 25 = $600,000.
That is reachable. At $30,000/yr saved with a 6% real return, she gets there in about eleven years.
What lean FIRE hides: the spending floor is fragile. A medical event, a roof, a divorce — any of these eats years of margin. Lean FIRE works for people who genuinely prefer the lower-budget life, not for people performing it. The forums are full of the second group, and they tend to quietly un-retire around month eighteen.
Fat FIRE
The same equation moved upmarket. Annual spending floor of $150,000+, so the number runs from $3.75M up.
Worked example: Daniel and Sarah, both 41, two kids, Manhattan. Honest spending is $180,000/yr (private school, two-bedroom co-op, the works). Their fat FIRE number is $180,000 × 25 = $4,500,000.
For most readers this is a fantasy line item, not a plan. Fat FIRE is functionally the version available to high earners in HCOL cities who don’t want to relocate or simplify. It is FIRE without lifestyle change. The variant is real but the readership is small.
What it hides: lifestyle inflation continues after you stop working. Fat FIRE often becomes Fatter FIRE, then Just-One-More-Year FIRE.
Coast FIRE
The hidden gem. The idea: save enough early that compound growth alone takes you to traditional-retirement spending by 65. After that point, you stop saving and let the portfolio coast. You can keep working — but at lower intensity, lower pay, lower stakes.
The math is the 25× number discounted backward at your expected return.
Worked example: Hannah, 33, wants $60,000/yr at age 65. Her age-65 number is $60,000 × 25 = $1,500,000. Discounted back 32 years at 6% real:
$1,500,000 ÷ (1.06)^32 ≈ $232,000
If she has $232,000 invested today, she never has to save another dollar to retire at 65 in current-dollar comfort. She still has to earn her living expenses for the next 32 years — but she does not have to save.
That changes everything. The next 32 years can be a part-time job, a small business, a teaching gig, a thing she’d actually do. The savings vise loosens. The trade is that you keep working, just not at full intensity.
What coast FIRE hides: it assumes you’ll actually downshift. Most people, once they’ve hit their coast number, just keep saving — because the habits don’t dissolve when the math says they can.
Barista FIRE
The US-specific patch. The original problem: your portfolio is large enough to cover most of your spending, but US health insurance under the ACA without subsidy can run $20,000+ a year for a family. Barista FIRE solves the gap with a part-time W-2 job that provides health insurance (the canonical example was Starbucks, hence the name).
Worked example: David, 49, has $700,000 invested and spends $42,000/yr. Pure FIRE at 25× would demand $1,050,000 — he is short. But: a 20-hour-a-week job at $20/hr nets ~$20,000/yr and includes health insurance. His portfolio now only needs to cover $22,000/yr. At 4%, that’s $550,000. He is over his real number.
| Variant | Spending floor | Portfolio needed (25×) | Who it’s for |
|---|---|---|---|
| Lean | $24,000 | $600,000 | Genuinely modest tastes |
| Pure | $55,000 | $1,375,000 | Mainstream, full exit |
| Fat | $180,000 | $4,500,000 | High earners, no lifestyle change |
| Coast | $232,000 now | n/a — coasts to $1.5M | Young savers, want to downshift work |
| Barista | $550,000 | with part-time job | US-specific, healthcare bridge |
What barista FIRE hides: the part-time job has to actually exist where you live, and the employer has to actually offer benefits at part-time hours, which is increasingly rare. Also, you are still working — and the 20-hour version often becomes 30 hours, then 35.
Which one is you?
Three variables determine which variant fits: your honest spending rate, your healthcare situation, and how much of your identity is wrapped in working.
If you can genuinely live on $30,000 and your healthcare is solved (expat, Medicaid-expansion state, spouse’s plan), lean FIRE is real. If you’re 33 with $200,000 and 30 years of compounding ahead, coast is the move and you’re already there or close. If you’re 49 in the US with no expat appetite and a $700,000 portfolio, barista is the bridge. If you’re earning $500,000 in New York and don’t want to leave, fat is honest about what you’re actually planning.
Pure FIRE is the default because it’s the cleanest equation. It’s also, for most readers, the wrong one. The 25× number is calibrated to a life that runs through age 95 with no Social Security, no part-time income, no geographic flexibility, and no honest horizon. If any of those assumptions don’t apply to you, your real number is smaller than the calculator says.
Pick the variant that matches your actual life. Then run that math. The result is closer than you think.
Next in this series: Healthcare Without a Job — Honest 2026 Numbers for US Early Retirees.
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