How to use the FIRE Calculator
- Enter your Current age and Target retirement age.
- Enter Current savings and Annual spending.
- Enter your Expected return and Annual savings.
- Read your FIRE number and timeline.
Worked example
Age 30, retire at 50, $50k saved, spend $40k/yr, save $20k/yr, 6% return.
- Current age: 30; Target age: 50; Spending: $40,000/yr
- Saved: $50,000; Annual savings: $20,000; Return: 6%
FIRE number: $1,000,000 (25× spending). Projected at retirement: $896,069 — on track to retire early.
The 4% rule and the FIRE number
FIRE uses the 4% rule: you can safely withdraw 4% of your portfolio per year. That means you need about 25× your annual spending invested. Cut spending and your target drops immediately.
FIRE number = Annual spending × 25
The 4% rule is a historical guideline, not a guarantee — sequence-of-returns risk in the first years of retirement is real.
Frequently asked questions
Why 25× spending?
Because 1 ÷ 0.04 = 25. It's the inverse of the 4% safe-withdrawal rate.
What if returns are lower?
Many FIRE planners use a 3% (33×) or 3.5% assumption for more safety, especially early retirement with a long horizon.
Does this include Social Security?
No. Many early retirees bridge to Social Security with a cash buffer; this tool shows the portfolio you'd need independent of it.