FIRE Number Calculator
Your FIRE number is the portfolio size you need to retire and live off investment returns forever. Drag the sliders to see your Lean, Standard, and Fat targets update instantly — all in today's dollars.
Your Numbers
Enter this to see your progress toward FIRE.
Minimalist lifestyle
Current lifestyle
Comfortable lifestyle
How this calculator works
The FIRE number is built on a single formula: annual expenses ÷ withdrawal rate. It tells you how large a portfolio must be so that X% drawn each year exactly covers your spending — forever.
With the classic 4% rule (from the 1998 Trinity Study), this simplifies to multiplying your annual expenses by 25. The study backtested balanced portfolios over historical US market data and found a very high probability of success over 30-year retirement windows.
The three variants:
- Lean FIRE — 60% of today's spending. Ideal for minimalist lifestyles or low cost-of-living relocations.
- Standard FIRE — 100% of today's spending. The most commonly cited target.
- Fat FIRE — 175% of today's spending. Provides a comfortable cushion for healthcare, family, and lifestyle upgrades.
All figures are in today's dollars using real (inflation-adjusted) returns. If you use a 5% real return, that already accounts for ~3% inflation built in.
Frequently Asked Questions
What is my FIRE number?
Your FIRE number is the total investment portfolio you need to retire and live off investment returns indefinitely. It equals your expected annual retirement expenses divided by your safe withdrawal rate. At the standard 4% withdrawal rate, your FIRE number is 25× your annual spending — so $50,000/year in expenses requires a $1,250,000 portfolio.
What is the 4% rule?
The 4% rule comes from the 1994 Trinity Study, which found that a balanced portfolio of stocks and bonds could sustain 30+ years of annual withdrawals at 4% with a high historical success rate. It's the most widely used benchmark in FIRE planning. People retiring very early (before 50) often prefer 3–3.5% to account for a longer retirement horizon.
What's the difference between Lean, Standard, Fat, and Chubby FIRE?
Lean FIRE targets a frugal retirement budget — typically 60% of current expenses. Standard FIRE replaces your current lifestyle exactly. Chubby FIRE adds a moderate cushion (roughly 110–135% of current expenses). Fat FIRE targets a significantly higher lifestyle (150%+). This FIRE calculator shows Lean, Standard, and Fat targets simultaneously — use the dedicated Lean, Chubby, or Fat FIRE calculators to customise the spending multiplier.
Should I use current or future expenses?
Enter your expected annual spending in retirement in today's dollars. If you plan to pay off your mortgage before retiring, subtract that payment. If you expect higher healthcare costs, build in a buffer. The calculator uses real (inflation-adjusted) returns, so entering today's dollars gives an answer in today's purchasing power — no separate inflation adjustment needed.
Does the FIRE number include home equity?
Typically no. Your FIRE number refers to liquid, investable assets such as index funds, stocks, and bonds. Owning a paid-off home reduces your annual expenses (no rent or mortgage payment), which lowers your FIRE number — but the home value itself is not usually counted as part of the investable portfolio.