Your FIRE number is the amount of money you need invested to cover your expenses for life — the point at which work becomes optional. It is the single most important number on the path to financial independence . Once you hit it, your investments generate enough income to replace your paycheck. The good news: calculating your FIRE number is surprisingly simple. The math takes about 30 seconds. The hard part is building the habits and systems to get there. This guide covers the formula, the variations, and how to adjust for the life you actually want. What Is a FIRE Number? FIRE stands for Financial Independence, Retire Early . Your FIRE number is the investment portfolio size that lets you live off the returns without ever running out of money. It is based on the 4% rule — a guideline from the Trinity Study that found a 4% annual withdrawal rate sustained a portfolio for at least 30 years in nearly every historical scenario.…