FIRE Number Calculator
Your FIRE number is the investment portfolio size that can sustain your lifestyle indefinitely — calculated as annual expenses × 25 (the 4% rule). This calculator shows your target, how long to reach it, and your projected retirement date.
Enter your annual expenses, current savings, monthly contribution, and expected return to see your FIRE number, years to financial independence, and portfolio growth timeline.
| Year | Portfolio Value | % of FIRE Number | Annual Income Supported |
|---|
How the FIRE Number Works
The FIRE number comes from the 4% rule, which emerged from the 1998 Trinity Study. Researchers found that a portfolio withdrawing 4% annually (inflation-adjusted) survived 30-year retirements in nearly all historical stock/bond scenarios back to 1926. The inverse — 1 ÷ 4% — gives you 25× annual expenses as the required portfolio size.
For early retirees with 40–50 year horizons, many practitioners use 3.5% (28× expenses) or 3.25% (31× expenses) for a larger safety margin. The 4% rule was designed for traditional 65-year retirements; applying it to a 35-year-old who plans to retire at 45 carries more sequence-of-returns risk over a longer period.
Savings Rate: The Real Driver of FIRE Timeline
The single most powerful lever in reaching FIRE is your savings rate. At 5% real returns:
| Savings Rate | Years to FIRE | Example (age 25 start) |
|---|---|---|
| 10% | 43 years | Retire at 68 |
| 25% | 32 years | Retire at 57 |
| 40% | 22 years | Retire at 47 |
| 50% | 17 years | Retire at 42 |
| 70% | 8.5 years | Retire at 33–34 |
LeanFIRE, FIRE, and FatFIRE
The FIRE community distinguishes several versions based on target spending. LeanFIRE: minimize expenses, typically under $40,000/year, FIRE number under $1M. Requires geographic arbitrage, frugality, or minimal lifestyle. Regular FIRE: comfortable middle-class lifestyle, $50,000–$80,000/year, FIRE number $1.25M–$2M. FatFIRE: high-income lifestyle maintained in retirement, $100,000+/year, FIRE number $2.5M+. Most people target regular FIRE; FatFIRE requires substantially higher income or longer accumulation period.
To see how much monthly income your portfolio can support once you reach FIRE, use the Retirement Income Calculator. For the full FIRE philosophy and historical context, read our guide on how to calculate your FIRE number.
Frequently Asked Questions
What is a FIRE number?
Your FIRE number is the investment portfolio size that can sustain your lifestyle indefinitely. It equals annual expenses × 25 (using the 4% rule). Spend $50,000/year → FIRE number is $1,250,000. At that size, you can withdraw 4% annually (inflation-adjusted) with historically high odds of never running out over 30 years.
How long does it take to reach FIRE?
Almost entirely determined by your savings rate. At 10% savings: ~43 years. At 25%: ~32 years. At 50%: ~17 years. At 70%: ~8.5 years. (Assuming 5% real returns, 4% SWR, starting from $0.) Increasing your savings rate matters far more than chasing higher investment returns.
What is LeanFIRE vs. FatFIRE?
LeanFIRE: minimal lifestyle, under $40K/year, FIRE number under $1M. Regular FIRE: comfortable middle-class, $50K–$80K/year, FIRE number $1.25M–$2M. FatFIRE: high spending maintained in retirement, $100K+/year, FIRE number $2.5M+. All versions use the same 25× formula; the difference is just the annual spending target.
Is the 4% rule safe for early retirement?
The 4% rule was tested against 30-year retirements. For 40–50 year FIRE horizons, many practitioners use 3.5% (28× expenses) for greater safety. Historical success rates at 4% over longer horizons are still 80%–90%, but not as robust. Early retirees often use flexible spending (cutting discretionary expenses in down markets) as an additional safety mechanism.
Should I include Social Security in my FIRE number?
If you'll work 10+ years, you'll likely qualify for Social Security starting at 62–70. Every $10,000/year in Social Security income reduces the required portfolio by $250,000 (at 4% SWR). Very early retirees (retiring at 35–45) typically can't count on Social Security in near-term planning but should model it as a supplement starting at 62.
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