Financial independence means your investment portfolio generates enough income to cover your expenses indefinitely, without requiring you to work. Your FIRE number is the specific portfolio value where that becomes true.
The number most people use, 25 times annual expenses, is a starting point. The exact FIRE number depends on your planned withdrawal rate, what other income you have, when you plan to stop working, and how much flexibility you have in spending.
The Standard FI Calculation
FI Number = Annual Expenses / Safe Withdrawal Rate
At a 4% withdrawal rate: FI Number = Annual Expenses x 25
| Annual Expenses | FI Number (4% rule) |
|---|---|
| $30,000 | $750,000 |
| $40,000 | $1,000,000 |
| $50,000 | $1,250,000 |
| $60,000 | $1,500,000 |
| $80,000 | $2,000,000 |
| $100,000 | $2,500,000 |
Adjusting for Guaranteed Income
Most FI calculations ignore Social Security, pensions, or rental income. These reduce how much your portfolio needs to generate.
Adjusted FI Formula:
FI Number = (Annual Expenses - Annual Guaranteed Income) / Safe Withdrawal Rate
Example: $60,000/year expenses, $24,000/year Social Security (at 67), 4% withdrawal rate.
- Portfolio needs to cover: $60,000 - $24,000 = $36,000/year
- FI Number: $36,000 / 0.04 = $900,000
That is $600,000 less than the standard calculation. The Social Security adjustment is significant.
But if you plan to retire at 45 and Social Security is 22 years away, you need the portfolio to cover full expenses for 22 years before Social Security kicks in. The calculation becomes more complex.
Early Retirement vs Traditional Retirement
The 4% rule was derived from 30-year retirement periods. Early retirees face 40-60 year horizons. A safer withdrawal rate for longer periods:
| Retirement Length | Suggested Withdrawal Rate |
|---|---|
| 30 years | 4.0% |
| 40 years | 3.5% |
| 50+ years | 3.0-3.25% |
At 3.25%, a $60,000 annual expense requires a $1,846,000 portfolio, $346,000 more than the 4% rule number.
Breaking Down Your Actual Retirement Expenses
Your FI number is only as good as your expense estimate. Most people underestimate retirement expenses.
Items to include in retirement spending:
- Housing (mortgage, rent, or equivalent maintenance on a paid-off home)
- Food
- Healthcare (especially before Medicare at 65)
- Transportation
- Travel and leisure (often increases in early retirement)
- Insurance (life, home, auto, umbrella)
- Property taxes
- Long-term care provisions
Items that typically drop in retirement:
- Payroll taxes
- Work-related expenses
- Retirement savings contributions
- Mortgage payments (if paid off)
- Some childcare and school costs
Run a detailed retirement budget rather than using a percentage-of-current-income estimate.
The Coast FI Number
Coast FI is the amount you need saved such that if you stop contributing, the portfolio will grow to full FI by retirement with no additional contributions.
At 7% real returns, money doubles every 10 years:
- If retirement is 30 years away and your FI number is $1,500,000
- Coast FI number: $1,500,000 / (1.07^30) = $197,000
If you have $197,000 invested at 30 years from your target retirement and stop contributing entirely, compounding does the rest.
The 4% Rule in Practice
The 4% rule is not a guarantee. It is a starting point based on historical US market data. It assumes:
- 60-70% equity, 30-40% bond allocation
- Annual withdrawals adjusted for inflation
- No adjustment to spending in bad years
Adding flexibility by reducing withdrawals 10-15% in market downturns dramatically extends portfolio survival and allows a higher initial withdrawal rate.
See Best Investing Platforms for retirement account management and portfolio tracking tools.
Use the CalcMoney FIRE Calculator to model your specific FI number with custom withdrawal rates, expenses, and income assumptions.
Frequently Asked Questions
Should I include home equity in my FI number?
Generally no, unless you plan to downsize or reverse mortgage. Home equity requires selling or borrowing to access. A paid-off home reduces expenses (no mortgage) but does not generate income. Count the expense reduction, not the equity value.
How does inflation affect my FI number?
Your FI number is in today's dollars. If you plan to retire in 15 years, your expenses in retirement will be higher due to inflation. Either calculate in real (inflation-adjusted) terms with a real return assumption, or inflate your current expenses to your retirement start date.
What withdrawal rate should I use if I have no other income?
For a very long retirement (45+ years) with no pension or Social Security, consider 3-3.5%. The extra cushion dramatically reduces the probability of portfolio depletion in a bad sequence-of-returns scenario.
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