A free, open-source FIRE (Financial Independence, Retire Early) calculator that runs in a single HTML file with zero dependencies.
Calculates your numbers for Coast FIRE, Barista FIRE, Fat FIRE, and Lean FIRE — instantly in your browser.
The math:
- FIRE Number = Annual Spending / 4% (Trinity Study safe withdrawal rate)
- Coast FIRE Number = FIRE Number / (1 + Real Return Rate)^Years
Default assumptions (all adjustable):
- Investment return: 10% (S&P 500 historical average)
- Inflation: 3%
- Safe withdrawal rate: 4%
- Real return: ~7%
No signup. No tracking. No server. Download the HTML file and run it offline.
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