Why do my expenses matter more than my income on the path to FIRE?

Expenses drive FIRE because they set both halves of the equation: lower spending means you need a smaller portfolio (25x of a small number is a small number) and you can save a larger share of every paycheck. A high earner who spends nearly everything has a low savings rate and a huge target, while a modest earner who lives lean can hit FI faster. Cutting $500 a month from recurring costs lowers your FIRE number by roughly $150,000 at 25x — and frees up $6,000 a year to invest. Income helps, but only to the extent it widens the gap between earning and spending. That's why people obsess over the big three — housing, transportation, and food — since those usually decide the savings rate. Map your real spending at wealthserene.com/tools/budget-analyzer.