Understanding Financial Independence, Retire Early (FIRE)
The FIRE movement is a lifestyle and financial strategy with the goal of gaining financial independence long before the traditional retirement age of 65. The core principle involves aggressively saving a high percentage of your income (often 50% or more) and investing it in low-cost index funds to build a self-sustaining portfolio.
The Mathematical Formula Used
This calculator relies on the legendary "4% Rule," derived from the Trinity Study. It dictates that you can safely withdraw 4% of your total investment portfolio each year (adjusted for inflation) without running out of money over a 30-year period.
FIRE Number = Annual Living Expenses × 25
To calculate how long it takes to reach that number, we run a continuous compounding loop:Balance = Balance × (1 + Return Rate) + Annual Savings
A Quick Practical Example
If your current lifestyle costs $40,000 per year, you need a FIRE Number of exactly $1,000,000 ($40k × 25).
- If you earn $100k, spend $40k, and save the remaining $60k every year.
- Starting from $0 at age 30, assuming a 7% real annual return.
- It will take you just over 10 years to hit your million-dollar target.
- You could theoretically fully retire at age 41.