FI Number Calculator

Calculate your Financial Independence number - the investment portfolio size needed to cover your expenses indefinitely.

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Quick Facts

The 4% Rule
25x Annual Expenses
Classic FI number formula
Conservative (3%)
33.3x Annual Expenses
For longer retirements
Trinity Study
96% Success Rate
4% rule over 30 years
Real Return
~4% / year
After inflation (historically)

Your FI Results

Calculated
FI Number
$0
Target portfolio size
Years to FI
0
At current savings rate
Progress
0%
Toward your FI number
Amount Remaining
$0
Still needed to reach FI
Safe Annual Withdrawal
$0
Your FI income per year
Safe Monthly Income
$0
Your FI income per month

Key Takeaways

  • Your FI number equals Annual Expenses / Withdrawal Rate
  • At a 4% withdrawal rate, you need 25 times your annual expenses
  • Lower expenses = lower FI number = faster path to financial independence
  • The Trinity Study showed a 4% withdrawal rate has a 96% success rate over 30 years
  • Consider using 3-3.5% for early retirement (40+ year timeframes)

What Is Your FI Number?

Your FI Number (Financial Independence Number) is the total amount of invested assets you need to cover your living expenses indefinitely without working. Once you reach this number, the returns from your investments can sustain your lifestyle, making work truly optional.

The concept is elegantly simple: if your investments can generate enough passive income to cover your expenses, you no longer need employment income. This is the core principle behind the FIRE (Financial Independence, Retire Early) movement that has helped millions achieve financial freedom.

The FI Number Formula

FI Number = Annual Expenses / Safe Withdrawal Rate
Annual Expenses = Your yearly living costs
Safe Withdrawal Rate = The percentage you can safely withdraw each year (typically 4%)

For example, if you spend $40,000 per year and use the traditional 4% withdrawal rate:

FI Number = $40,000 / 0.04 = $1,000,000

FI Numbers at Different Expense Levels (4% Rule)

$30K/year $750,000
$50K/year $1,250,000
$80K/year $2,000,000

Understanding the Safe Withdrawal Rate

The Safe Withdrawal Rate (SWR) is the percentage of your portfolio you can withdraw each year with a high probability of not running out of money. The famous "4% Rule" comes from the Trinity Study, which analyzed historical market returns and found that a 4% initial withdrawal rate (adjusted annually for inflation) had a 96% success rate over 30-year periods.

Which Withdrawal Rate Should You Use?

Conservative
3%
33.3x expenses
Moderate
3.5%
28.6x expenses
Traditional
4%
25x expenses
Aggressive
5%
20x expenses

Pro Tip: Adjust for Early Retirement

If you're retiring in your 30s or 40s, consider using a 3-3.5% withdrawal rate instead of 4%. A 50-year retirement requires more conservative planning than the 30-year period the Trinity Study analyzed. Many early retirees also maintain some flexibility in spending or keep small income sources as additional safety margins.

Two Ways to Reach FI Faster

There are only two levers to accelerate your path to financial independence:

1. Reduce Your Annual Expenses

Every $100 you cut from your monthly expenses reduces your FI number by $30,000 (at a 4% withdrawal rate). This is often the most powerful lever because it simultaneously:

  • Lowers the amount you need to save
  • Increases the amount you can save each month
  • Proves you can live on less, giving confidence for retirement

2. Increase Your Savings Rate

The more you save and invest, the faster your portfolio grows toward your FI number. A 50% savings rate gets you to FI in roughly 17 years starting from zero. A 75% savings rate can do it in about 7 years.

Lean FIRE vs. Fat FIRE

The FIRE community recognizes different "levels" of financial independence:

  • Lean FIRE: FI number based on minimal expenses ($20,000-$40,000/year). Requires $500K-$1M portfolio. Fastest to achieve but requires frugal lifestyle.
  • Regular FIRE: FI number based on moderate middle-class expenses ($40,000-$60,000/year). Requires $1M-$1.5M portfolio.
  • Fat FIRE: FI number based on comfortable or affluent expenses ($80,000-$150,000+/year). Requires $2M+ portfolio. Takes longer but provides more cushion.

Common FI Number Mistakes to Avoid

  • Forgetting healthcare costs: Before Medicare (age 65 in the US), you'll need to budget for health insurance, which can cost $500-$1,500+/month.
  • Not accounting for taxes: Withdrawals from traditional 401(k)s and IRAs are taxed as ordinary income.
  • Ignoring expense changes: Your expenses may change in retirement - some costs decrease (commuting, work clothes) while others may increase (healthcare, hobbies).
  • Calculating based on gross income: Your FI number should be based on expenses, not income replacement.
  • Not stress-testing your plan: Consider what happens if markets drop 40% right after you retire (sequence of returns risk).

Your Next Steps

Use the calculator above to find your personal FI number. Then:

  • Track your actual expenses for 3-6 months to get accurate numbers
  • Calculate your current savings rate
  • Automate your investments to hit your monthly savings target
  • Review and adjust annually as your expenses and goals evolve

Financial independence is not about deprivation - it's about aligning your spending with your values and building a life where work is optional. Your FI number is simply the math that makes freedom possible.