Retirement & investing · free calculator
FIRE number calculator
Compute your Financial Independence / Retire Early target — Lean FIRE, regular FIRE, Fat FIRE — based on annual spending and safe withdrawal rate.
Years to FIRE
Show the work
- FIRE number$1,250,000
- Lean FIRE (spend × 25 ÷ 1.4)$892,857
- Fat FIRE (spend × 25 × 1.5)$1,875,000
FIRE — the math is the easy part
The FIRE math is simple: 25× annual spending = the portfolio that supports it indefinitely at 4% withdrawal. The hard parts are the assumptions: how stable is your spending, what's your real return, what's your post-FIRE healthcare plan?
The three FIRE flavors
- Lean FIRE (~$25-40k/yr spend): smaller portfolio, requires lifestyle compression. Often abroad or in low-cost-of-living areas.
- Regular FIRE (~$40-80k/yr spend): mid-tier, $1-2M portfolio
- Fat FIRE (~$100k+/yr spend): suburban-comfortable, $2.5M+ portfolio
What the math doesn't capture
- Healthcare gap — pre-65 health insurance pre-Medicare. ACA subsidies make this manageable for low-income retirees but require staying under MAGI thresholds. Real cost: $400-1,200/month per person.
- Sequence-of-returns risk — first 5-10 years of retirement returns determine 30-year survivability more than average return. Bad early years can sink an otherwise solid plan.
- Lifestyle creep — your actual spending in retirement tends to grow with portfolio. The 4% number is calibrated on inflation-adjusted constant spending.
- Family changes — divorce, kids' weddings, parent care. The $50k/yr spend assumption is fragile.
Why 4% works (and when it doesn't)
Bengen's 1994 study tested 4% across all 30-year retirement periods 1926-1990. It survived. But:
- 50-year retirements (FIRE at 35): 4% fails ~10% of historical paths. Drop to 3.5%.
- International equity weighting matters; Bengen used 100% US.
- Trinity Study (1998) backed 4% with broader portfolios; recent updates push it to 4.5% for 60/40 portfolios.
Export
CSVPrintable PDFEmbedNot sure which calc you need? Ask →Related calculators