FIRE Calculator
Formula and Calculation Method
FIRE Number and savings rate calculations:
FIRE Number = Annual Living Expenses ÷ Safe Withdrawal Rate (e.g., 0.035 to 0.04)Savings Rate (%) = (Annual Savings ÷ Annual Take-Home Income) × 100
Common FIRE variations:
- Lean FIRE: Living on frugal expenses (<$40,000/yr).
- Regular FIRE: Maintaining median household lifestyle ($50,000–$90,000/yr).
- Fat FIRE: Abundant, unconstrained retirement living ($100,000+/yr).
Worked Example and Step-by-Step Calculation
- Annual Net Income: $110,000
- Annual Living Expenses: $55,000
- Annual Savings: $55,000 (50% savings rate)
- Current Portfolio: $120,000
- Expected Real Return (after inflation): 6.0%
- Safe Withdrawal Rate: 3.75%
1. Target FIRE Number = $55,000 ÷ 0.0375 = $1,466,667
2. Net worth growth from $120,000 initial + $55,000 annual additions at 6% real return.
3. Years required to cross $1,466,667 = 13.4 years.
How to Use the FIRE Calculator
- Enter your annual post-tax household income and annual living expenses.
- Input your current invested portfolio value in stocks, bonds, and ETFs.
- Select your safe withdrawal rate (typically 3.5% for early 40+ year retirements or 4.0% for traditional horizons).
- Choose your target return rate after inflation (5% to 7% real).
- Review your Lean, Standard, and Fat FIRE milestones and exact years to retirement.
Common Mistakes, Limitations & Practical Guidance
- Early retirement spanning 40 to 50 years faces greater sequence-of-returns risk than traditional 30-year retirements, often requiring a 3.25% to 3.75% SWR.
- Pre-Medicare private health insurance costs must be budgeted into early retirement living expenses.
Frequently Asked Questions About FIRE Calculator
How is your FIRE number calculated?
Your Financial Independence number equals your anticipated annual retirement living expenses multiplied by 25 (under the 4% rule) or 30 to 33 (under a conservative 3.0% to 3.3% safe withdrawal rate for early retirements).
What is a FIRE number?
Your FIRE number is the total net worth invested in income-producing assets needed to cover your living expenses permanently without requiring earned employment income, typically calculated as 25 to 30 times your annual expenses.
Why is savings rate so important in the FIRE movement?
Your savings rate matters more than your absolute salary. A 50% savings rate means you save one year of living expenses for every single year you work. At a 65% savings rate, you can reach financial independence in approximately 10 to 11 years starting from zero.
What is the difference between Lean FIRE, Barista FIRE, and Fat FIRE?
Lean FIRE involves retiring on a minimalist, low-cost budget (<$40,000/yr). Barista FIRE means having enough investments to cover major expenses while working a low-stress or part-time job for healthcare. Fat FIRE covers a luxurious lifestyle ($100k-$150k+/yr).
Is the 4% rule safe for a 40-year or 50-year early retirement?
The original 4% rule was tested for a 30-year horizon. For early retirees who retire in their 30s or 40s expecting 50+ years of withdrawals, financial researchers recommend a more conservative Safe Withdrawal Rate between 3.25% and 3.75%.
How is the FIRE Calculator different from the standard Retirement Calculator?
Our standard Retirement Calculator targets conventional retirement ages (60-67) with Social Security integration. This FIRE Calculator models aggressive savings rates (30% to 70%), multi-decade early retirement horizons, and flexible spending tiers.