How do I calculate my FIRE number?

Your FIRE number is the total portfolio size needed to fund your retirement indefinitely using the 4% safe withdrawal rate. Formula: annual spending × 25. For example, if you spend $50,000/year, your FIRE number is $1,250,000. To retire on $80,000/year, you need $2,000,000. Use this as a starting point — actual needs vary based on healthcare, taxes, lifestyle changes, and market conditions in early retirement.