What is the 25x Rule? The 25x Rule is a FIRE shortcut stating that your FI Number equals 25 times your expected annual expenses, the arithmetic inverse of a 4% Safe Withdrawal Rate. It converts any spending level into a concrete savings target in one multiplication, making FIRE planning accessible without spreadsheets.
Examples:
| Annual expenses | 25x FI Number |
|---|---|
| $30,000 | $750,000 |
| $50,000 | $1,250,000 |
| $80,000 | $2,000,000 |
| $120,000 | $3,000,000 |
Because expenses, not income, drive the target, the rule highlights FIRE’s core insight: every $1,000 cut from annual spending reduces the required portfolio by $25,000. Refinancing a mortgage to save $300/month ($3,600/year) slashes your FI Number by $90,000. That is why expense optimization beats income optimization in the final miles of the FIRE journey.
Use conservative variants for very early retirement: 28x (3.5% SWR) or 33x (3% SWR) build in buffer for sequence risk, healthcare shocks, and 50+ year horizons. The 25x Rule is the starting point, not the finish line.