FIRE number calculator
Your FIRE number is the invested corpus that can, in a simple model, cover a year of spending at a chosen safe withdrawal rate (SWR).
FIRE number = Annual expenses ÷ (SWR ÷ 100)
At 4% SWR: FIRE number = Annual expenses × 25
$40,000 of annual spending at 4% SWR → $1,000,000. That is 25 years of expenses if the portfolio never grew and you took a flat dollar amount — a teaching shortcut, not a forecast.
What this page does
- Converts monthly spending to annual (×12).
- Lets you edit the SWR (3%, 4%, 5%…).
- Labels amounts as USD, MXN, or GTQ. It does not convert currencies.
What this page does not do
- Sequence-of-returns risk, taxes, account fees, or inflation paths.
- Social Security, pensions, or part-time work (see FIRE types for Lean / Fat / Barista).
- Monte Carlo or advisor recommendations.
Sources (educational)
The 4% rule is commonly traced to William Bengen (1994) and later discussed in the Trinity Study (Cooley, Hubbard, and Walz). NEED-SOURCE: those papers are not stored as PDFs on this site. Treat 4% as a teaching default, not a promise.
This is an educational calculator. A real plan depends on your tax system, healthcare, family, and markets. Returns and inflation are assumptions you type in.
Next tools in this series
- Years to FI — savings rate → years.
- Coast FIRE — how much you need today to stop contributing.
- FIRE types — Lean, Fat, and Barista on one page.
- Safe withdrawal — $1,000,000 at 4% → $40,000/year.
Because 1 ÷ 0.04 = 25. If you spend $40,000 and withdraw 4% of a portfolio each year, you need $40,000 ÷ 0.04 = $1,000,000.
Yes. Switch the currency label. The math is the same; we do not apply an FX rate.
No. It is a teaching model. It does not replace a planner, tax rules, or your own research.