FIRE Number Formula
The FIRE Number formula provides the crucial target for your investment portfolio, representing the total assets needed to fund your desired lifestyle in early retirement, based on your annual spending and a sustainable withdrawal rate.
Formula
Copy the exact expression or work through it step by step below.
FIRE Number = Annual Spending / Withdrawal Rate Variables
FN
FIRE Number
The fire number value plugged into the fire number calculation.
AS
Annual Spending
The annual spending value plugged into the fire number calculation.
WR
Withdrawal Rate
The withdrawal rate assumption used in the fire number calculation.
Step By Step
- 1
Set the baseline case with the real calculator inputs.
Current Age = 34, Current Portfolio = 180,000, Annual Spending = $52,000, Annual Savings = $24,000
- 2
Translate rates, periods, and cash values onto the same footing before combining them.
Keep the fire number assumptions consistent instead of mixing monthly and annual views.
- 3
Apply the formula and read the first calculator outputs, not just the headline assumption.
The calculator lands with target portfolio at 1,300,000 and lean target portfolio at 1,040,000.
- 4
Run one changed scenario so the formula is stress-tested before it is trusted.
The fire calculator page is the fastest way to compare that second case.
Worked Example
FIRE Number sample case
Current Age
34
Current Portfolio
180,000
Annual Spending
$52,000
Annual Savings
$24,000
FIRE Number = Annual Spending / Withdrawal Rate using current age 34, current portfolio 180,000, annual spending $52,000, annual savings $24,000.
The calculator lands with target portfolio at 1,300,000 and lean target portfolio at 1,040,000.
Common Variations
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Sources & References
- Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable — Fidelity Investments
- The Trinity Study: A Historical Look at Withdrawal Rates — AAII Journal
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