Financial Independence Calculator (FIRE)
Calculate when you can retire early with the FIRE method.
See how savings rate, investments, and expenses determine your financial independence date.
Financial independence (FI) means your investment portfolio generates enough passive income to cover all living expenses indefinitely. The core calculation uses the 4% Safe Withdrawal Rate (SWR) derived from the Trinity Study — a landmark analysis of 30-year retirement survival rates across historical market conditions.
FI Number Formula:
FI Number = Annual Expenses / Safe Withdrawal Rate
Using the standard 4% SWR: FI Number = Annual Expenses × 25
Years to FI Formula:
This requires compound growth calculation — there’s no simple closed form, but the following estimate works for planning: Years ≈ [ln(FI Number / Current Portfolio) − ln(1 − (Savings Rate))] / ln(1 + Return Rate)
Worked example: Annual expenses: $48,000 FI Number = $48,000 × 25 = $1,200,000
Current portfolio: $120,000 Monthly savings: $2,000 ($24,000/year) Expected real return: 7%/year
Using calculator: approximately 22–24 years to FI.
Impact of savings rate on years to FI (7% return, starting from zero):
| Savings Rate | Years to FI |
|---|---|
| 10% | ~40 years |
| 20% | ~32 years |
| 30% | ~26 years |
| 50% | ~16 years |
| 70% | ~8 years |
Variations on the 4% rule:
- 3% SWR (FI × 33): more conservative, suitable for 40+ year retirements
- 3.5% SWR (FI × 28.6): common choice for early retirees
- 5% SWR (FI × 20): used when retirement is 20 years or less
Income sources (Social Security, pension, rental income) reduce the portfolio target dollar-for-dollar: Adjusted FI = (Expenses − Passive Income) × 25