How to Use the FIRE (Financial Independence, Retire Early) Calculator
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1
Enter your current age and target early retirement age.
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2
Provide your current invested portfolio value, annual after-tax income, and living expenses.
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3
Adjust expected real investment returns (typically 7% after inflation) and Safe Withdrawal Rate (typically 4%).
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4
Inspect your Standard FIRE Number, Lean FIRE, Fat FIRE, and Coast FIRE milestones.
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5
Review the exact number of years remaining and your projected monthly passive income.
Practical Example & Use Case
A 28-year-old with $65,000 saved and $45,000 annual expenses discovers that with a 47% savings rate, they will reach financial independence in 13.2 years at age 41.2 with a $1,125,000 nest egg.
Technical Notes & Limitations
Uses deterministic compounding and the Trinity Study 4% safe withdrawal rule. Does not factor unpredictable tax legislation or black swan market downturns.
Frequently Asked Questions
What is the 4% Safe Withdrawal Rule?
Originating from the Trinity Study, the 4% rule states that a retiree can withdraw 4% of their initial portfolio value in year one (adjusted for inflation thereafter) with a 95%+ probability of lasting 30+ years.
What is the difference between Lean FIRE, Fat FIRE, and Coast FIRE?
Lean FIRE covers basic bare-bones expenses (75%), Fat FIRE allows luxury spending (125%), and Coast FIRE is the amount needed in your portfolio today that will grow to your full retirement number by age 65 without saving another dollar.
Why is Savings Rate the most critical metric?
Your savings rate simultaneously increases the amount you invest each month while reducing the annual expenses your portfolio needs to replace.