What Is FIRE (Financial Independence, Retire Early)?
FIRE is a strategy where you save and invest aggressively—typically 50% or more of your income—so you can cover all living expenses from investment returns alone. Once your portfolio generates enough passive income to replace your paycheck, you're financially independent. You don't have to stop working, but you never have to work for money again.
The math is surprisingly simple: divide your annual expenses by your safe withdrawal rate (usually 4%). If you spend $50,000/year, your FIRE number is $1,250,000. If you spend $80,000/year, it's $2,000,000. The lower your expenses, the faster you get there—and the smaller the portfolio you need.
The 4% Rule and Why It Works
The 4% rule comes from the 1998 Trinity Study, which analyzed every 30-year rolling period from 1926 to 1995. A retiree who withdrew 4% in year one (adjusting for inflation each year after) had a 95% success rate of not running out of money over 30 years. For early retirees with a 40+ year horizon, many FIRE practitioners target 3.5% or build a buffer.
In practice: a $1,250,000 portfolio at 4% yields $50,000/year—or $4,167/month—in passive income. That number adjusts upward each year with inflation, and the remaining portfolio keeps compounding.
How Savings Rate Determines Your Timeline
Your savings rate is the single biggest lever in FIRE. More than investment returns, more than income—the percentage you save determines how many years until financial independence.
| Savings Rate | Years to FIRE | FIRE Age (Starting at 25) |
|---|---|---|
| 10% | 51 years | 76 |
| 25% | 32 years | 57 |
| 50% | 17 years | 42 |
| 75% | 7 years | 32 |
Assumes 7% real returns and starting from $0. At a 10% savings rate, you're working until traditional retirement age. At 50%, you cut that to 17 years. At 75%, you're financially independent before your friends finish paying off student loans.
Coast FIRE vs Lean FIRE vs Fat FIRE
Coast FIRE means you've saved enough that compound growth alone will carry you to full FIRE by traditional retirement age (65). You still need to cover current expenses, but you can stop investing entirely. A 30-year-old with $250,000 invested at 7% returns will have over $1.9 million by 65 without adding another dollar.
Lean FIRE targets a bare-bones lifestyle—typically 70% of your current expenses. If you spend $50,000/year, Lean FIRE requires $875,000 (at 4% withdrawal). This works for people willing to live frugally, move to a lower-cost area, or rely on part-time income to supplement.
Fat FIRE means financial independence with no lifestyle compromises—usually 150% or more of current spending. At $50,000/year in expenses, Fat FIRE is $1,875,000. This gives you a buffer for travel, healthcare surprises, and lifestyle inflation without anxiety.
5 Common FIRE Mistakes
1. Ignoring healthcare costs. Before 65, you don't have Medicare. Budget $500–$1,500/month per person for ACA marketplace plans. This alone can add $300,000+ to your FIRE number.
2. Using nominal returns instead of real returns. A 10% average market return is ~7% after inflation. Use 5–7% in your projections, not 10–12%. Overly optimistic returns lead to retiring too early with too little.
3. Forgetting about taxes. Withdrawals from traditional 401(k) and IRA accounts are taxed as income. A $50,000/year withdrawal might need $55,000–$60,000 gross depending on your state. Plan for the tax drag.
4. Lifestyle creep after hitting Coast FIRE. Once you stop aggressively saving, expenses tend to expand. Track spending even after you pass Coast FIRE—a $10,000/year increase in spending adds $250,000 to your FIRE number.
5. Skipping the withdrawal strategy. The 4% rule is a starting point, not a rigid formula. Build a plan that includes variable withdrawals (spend less in down markets), a cash buffer of 1–2 years of expenses, and Roth conversion ladders for tax efficiency.
To model how your investments compound over time, use the compound interest calculator. For traditional retirement planning with Social Security considerations, try the retirement calculator. To set intermediate milestones on the path to FIRE, check the savings goal calculator.