Find Your FIRE Number in 30 Seconds

Your FIRE number is the total investment portfolio size you need to retire early and sustainably live off investment returns. It equals your annual expenses × 25, based on the 4% safe withdrawal rate — a figure validated by the Trinity Study. For example, if you spend $50,000/year, your FIRE number is $1,250,000.

The 4% rule states you can safely withdraw 4% of your investment portfolio annually in retirement without running out of money over a 30+ year horizon. It was established by the 1998 Trinity Study analyzing historical US stock and bond returns. Many FIRE planners use 3.5% for longer retirements or higher equity exposure.

Savings rate is the single biggest lever. At a 10% savings rate it takes ~43 years; at 25% it's ~32 years; at 50% it's ~17 years; at 75% it's only ~7 years. This is because a higher savings rate both grows your portfolio faster AND reduces your FIRE number (since you need less to sustain lower spending).

Coast FIRE is reached when your current investments, left to grow untouched, will compound to your full FIRE number by your target retirement age — even if you stop adding money today. Many pursue Coast FIRE first: once reached, you only need to cover current expenses without saving, giving you much more lifestyle freedom.

Lean FIRE is retiring on a very frugal budget (typically under $40k/year), Regular FIRE targets the standard 4% rule, and Fat FIRE means retiring with a larger portfolio for a comfortable lifestyle (typically $100k+/year spending). The "right" variant depends on your desired lifestyle and flexibility tolerance.