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Finance

FIRE Number Calculator (Financial Independence)

Enter your projected annual spending in retirement (everything — housing, food, healthcare, leisure, taxes) and the safe withdrawal rate you plan to use (SWR, default 4% — the Bengen 1994 / Trinity Study standard). The tool instantly returns your FIRE number — the portfolio size required for financial independence: FIRE = annual spending ÷ SWR. The 4% SWR corresponds to the "25× rule" of thumb. Alongside it the tool shows three common community benchmarks: Lean FIRE (frugal, 0.7×), Fat FIRE (generous, 2×), and Coast FIRE @ 25 / 35 years — the "seed today" amount that, at a 4% real return and zero further contributions, will compound up to the full FIRE number by retirement. Runs entirely client-side. Suited for FIRE-movement planners, long-term retirement strategy and any financial-independence goal-setting exercise.

FIRE number

$1,000,000

25.0× annual

Monthly spend: $3,333

Lean FIRE

Fat FIRE

Coast FIRE @ 25 yr

Coast FIRE @ 35 yr

FIRE number = annual spending ÷ SWR; the 4% SWR is the "25× rule" (Trinity Study). Lean = 0.7× and Fat = 2× are community benchmarks. Coast FIRE = FIRE ÷ (1.04)ⁿ assumes a 4% real return and no further contributions to retirement. Investment risk, market sequence, taxes and inflation all affect the real number — use this as a planning anchor, not a guarantee.

Formula

FIRE = annual spending ÷ SWR; Lean FIRE = 0.7 × FIRE; Fat FIRE = 2 × FIRE; Coast FIRE (n yr) = FIRE ÷ (1.04)ⁿ

Frequently asked

Is the 4% rule still safe today?

It depends on your retirement length and asset mix. Bengen's original work targeted a 30-year retirement on a US 50/50 stock-bond portfolio using 1926–1992 historical data. For a 40–60-year early retirement, or under reduced-return assumptions (Vanguard, GMO and others project 2–4% real over the next decade), most research suggests dialling SWR down to 3.0–3.5% (i.e. 28–33× rule). Bengen himself published in 2020 that a more diversified portfolio could support up to 4.7%. The tool defaults to 4%, but you should tune it to your own horizon and risk tolerance.

Should the FIRE number include taxes and healthcare?

Yes — be inclusive. "Annual spending" should be the gross outflow after taxes, insurance premiums (US healthcare especially), expected medical costs and an emergency buffer. Social Security, occupational pensions (US 401(k), UK state pension, MPF in Hong Kong) can be deducted from required portfolio income if you trust them to land, but the conservative approach is to leave them as a margin of safety. The tool gives you the FIRE number for the total spending you input — choose how much of it you want the portfolio alone to cover.

Why are Lean / Coast / Fat fixed at 0.7× / 25 yr / 2×?

These are community conventions, not strict definitions. Lean FIRE refers to a tighter lifestyle than typical middle-class spending — r/leanfire targets roughly $25k–$40k/year in the US, ~0.7× the median FIRE budget. Fat FIRE means a generous, $100k–$200k+ lifestyle — about 2× a typical budget. Coast FIRE at 25/35 years brackets the common case of hitting Coast at 40–55 and retiring around 60–65. Tune the multipliers if your situation differs — the math is straightforward (Lean target = your_factor × FIRE).

Is the 4% real return used for Coast FIRE too optimistic?

4% real is the long-run historical average — Robert Shiller's data 1900–2024 puts S&P 500 total return ~6–7% real, and a 60/40 stock-bond mix lands around 4–5% real over multi-decade windows. Short-term and sequence risk are another matter: 2000–2010 was a "lost decade" near 0% real, while the 2010s ran 7–10%. Coast FIRE assumes you have ≥ 25 years for the average to assert itself, so 4% is the mainstream choice. Conservatives use 3%; aggressive planners use 5%. The tool fixes it at 4% for the labelled Coast columns — if you want a different rate, recompute manually as FIRE / (1 + r)ⁿ.

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