Your FIRE Number: How to Calculate Lean, Regular, Fat, and Coast FI Targets

The Basic Formula

FIRE number = annual spending ÷ withdrawal rate. At 4%: spending × 25. At 3.5%: spending × 28.6. At 3%: spending × 33.3. A lower rate is more conservative and suits longer retirements, such as 40 or 50 years, because the original 4% studies looked at 30-year periods.

Use your actual annual spending, not income. Spending is what the portfolio must replace, and it can be reduced by lowering your cost of living, which both shrinks the target and boosts your savings rate.

Lean, Regular, and Fat FIRE

Lean FIRE means retiring on a frugal budget, often under $40,000 a year for a household. Regular FIRE covers a middle-class lifestyle, perhaps $60,000 to $100,000. Fat FIRE implies a comfortable or luxurious lifestyle, typically spending above $100,000. The numbers depend heavily on your location, family size, and housing costs. A person with a paid-off home and low costs may need far less than the national averages.

Barista FIRE is a hybrid in which part-time income covers some expenses, so the portfolio must cover only the gap. If part-time work covers $15,000 of a $40,000 budget, the portfolio needs to supply $25,000, requiring $625,000 at 4%.

Coast FI

Coast FI is the point at which your current investments, with no further contributions, will grow to your FIRE number by traditional retirement age. The formula: coast number = FIRE number ÷ (1 + r)^years. If you need $1,000,000 at age 60 and expect a 5% real return, then at age 35 (25 years away) you need $1,000,000 ÷ 1.05^25 = $295,300 invested. After that, you only need to earn enough to cover current expenses.

This is attractive for people who want to downshift to lower-paying, more satisfying work without sacrificing retirement later.

Years to FI

With a starting portfolio of zero, a savings rate s, and a real return of 5%, the time to reach 25 times spending falls rapidly with higher savings rates: about 37 years at 20%, 22 years at 40%, and 17 years at 50%. A starting balance and rising income shorten the timeline. Use a retirement calculator for your own figures.

Risks and Adjustments

The 4% rule worked in the historical US data for 30-year retirements, but early retirees face sequence-of-returns risk: poor market returns in the first years can deplete a portfolio. Health insurance before Medicare eligibility is a major cost in the US. Inflation, taxes, and unplanned expenses matter. Many early retirees keep flexibility by adjusting spending, earning some income, or holding a cash buffer. Review your withdrawal rate each year rather than treating it as fixed forever.