Home » Planning » FI Number

Financial Independence Number Calculator

Calculate the exact amount you need to never work again. Based on the 4% rule and your actual annual expenses.

Your data stays in your browser. Nothing is stored or sent to any server.

Enter Your Details

The Math Behind Financial Independence

Financial independence (FI) is the point where your investment income covers all living expenses — work becomes optional. The formula is elegantly simple: FI Number = Annual Expenses ÷ Withdrawal Rate. At the standard 4% withdrawal rate: $48,000/year expenses requires $1,200,000. At 3.5% (more conservative): $1,371,429. At 3% (very conservative): $1,600,000.

The 4% rule comes from the Trinity Study (1998, updated), which found that a portfolio of 50-75% stocks and 25-50% bonds, withdrawing 4% in year one and adjusting for inflation each year, survived 95-100% of all 30-year periods in market history. For retirements longer than 30 years (early retirees), a 3.25-3.5% rate is safer. The most powerful lever is reducing expenses: cutting annual spending from $60,000 to $48,000 reduces your FI number by $300,000 — equivalent to years of additional saving. Build your budget with our 50/30/20 Budget Calculator.

Accelerating Your Path to FI

Increase your savings rate. The savings rate is the single most important variable in reaching FI. At 10% savings rate: ~40 years to FI. At 25%: ~30 years. At 50%: ~15 years. At 70%: ~8 years. Every percentage point matters exponentially. Optimize the big three: Housing (aim for 25% of income or less), transportation (used cars, minimize commute), and food (cook at home). These three categories account for 60-70% of most budgets. Increase income while keeping expenses flat. Every raise or side income dollar that goes to investing (not lifestyle inflation) accelerates FI dramatically. Track lifestyle creep with our Lifestyle Inflation Calculator and model your timeline with our FIRE Calculator.

People Also Ask

What is the 4% rule?
Withdraw 4% of your portfolio in year one, then adjust the dollar amount for inflation each year. Historical data shows this has a 95%+ success rate over 30 years. Example: $1.2M portfolio → $48,000/year first withdrawal.
How much do I need to retire at 40?
Depends on expenses. At $48,000/year expenses and 3.5% withdrawal rate (safer for long retirements): $1,371,000. At $36,000/year expenses: $1,028,000. Reducing expenses is as powerful as increasing savings.
Does the 4% rule account for Social Security?
No — Social Security is a bonus. When SS kicks in (typically age 62-67), you can reduce portfolio withdrawals, significantly extending portfolio longevity.
What is Coast FI?
The point where your existing savings, without any additional contributions, will grow to your FI number by traditional retirement age (65-67). For a 30-year-old with $200,000 saved and a $1.2M target: $200,000 × 1.07^35 = $2.15M — already past Coast FI.