FatFIRE is financial independence without the frugality. Where standard FIRE plans often assume $40,000 to $60,000 of yearly spending, FatFIRE aims for a retirement that supports $100,000, $200,000, or more per year: the house in a good school district, travel, help with kids' tuition, generous giving.
The math scales directly. At a 4% withdrawal rate, $100,000 of spending needs $2,500,000. $200,000 needs $5,000,000. Many FatFIRE planners use a more conservative 3% to 3.5% because their retirements are long and their spending is less flexible, which pushes the targets higher still: $200,000 at 3.5% needs about $5,700,000.
It is the natural version of FIRE for people with high and lumpy incomes. A household earning $400,000 with a mix of salary, bonus, and equity can plausibly save $150,000 or more a year, and at that pace a $5,000,000 target is a fifteen- to twenty-year project rather than a fantasy.
The common mistake is letting the target chase the lifestyle. Each new expense that becomes permanent adds 25 to 30 times its annual cost to the number you need. A $20,000-a-year car habit is a $500,000 to $600,000 addition to the finish line. FatFIRE works when you decide the spending level first and hold it, rather than letting equity windfalls set it.