What is a FIRE number?
A plain-English guide to the portfolio multiple that underpins Lean, Regular, and Fat FIRE.
Your FIRE number is the size of the invested portfolio that can support a chosen lifestyle without relying on a traditional paycheck. The classic starting formula is simple: annual spending divided by a safe withdrawal rate.
The 25× rule of thumb
At a 4% withdrawal rate, you need 25 times annual spending (because 1 ÷ 0.04 = 25). Spending $60,000 per year implies a $1.5 million FIRE number. Lower withdrawal rates (3–3.5%) mean larger multiples and more buffer for long early-retirement horizons.
Lean, Regular, and Fat
- Lean FIRE: lower spending target; frugal but intentional lifestyle.
- Regular FIRE: middle-class comfort in retirement spending.
- Fat FIRE: higher discretionary spending — travel, housing, hobbies.
These labels are not academic categories. Use them as presets, then replace them with your actual budget. Taxes, healthcare, and housing choices matter more than the nickname.
Try the free FIRE Number calculator at /calculators/fire-number, then stress-test withdrawal rates on the Methodology page and the SWR guide on this blog.