Short answer: Lean FIRE and Fat FIRE aren’t official categories. They are informal labels for retiring on a modest budget or a generous one, and there’s no agreed dollar line between them. What matters is your own yearly spending in retirement, because your FIRE number is that figure divided by your withdrawal rate: 25 times spending at 4%, about 28.6 times at 3.5%. Build the number from a budget, not a label.
Three example budgets
These are hypothetical budgets for one household, in today’s dollars, to show how the pieces add up. They are assumptions, not data; real costs depend heavily on where you live and who you support.
| Yearly spending | Lean example | Middle example | Fat example |
|---|---|---|---|
| Housing (rent or mortgage, tax, insurance, upkeep) | $14,400 | $21,600 | $36,000 |
| Food | $6,000 | $9,000 | $14,400 |
| Transportation | $3,000 | $7,200 | $12,000 |
| Health insurance and care | $6,000 | $8,400 | $12,000 |
| Travel | $1,500 | $5,000 | $15,000 |
| Everything else | $5,100 | $8,800 | $20,600 |
| Total | $36,000 | $60,000 | $110,000 |
What each budget needs invested
| Budget | Yearly spending | FIRE number at 4% | FIRE number at 3.5% |
|---|---|---|---|
| Lean example | $36,000 | $900,000 | $1,028,571 |
| Middle example | $60,000 | $1,500,000 | $1,714,286 |
| Fat example | $110,000 | $2,750,000 | $3,142,857 |
The gap is large. The fat example needs three times what the lean one does, and at the same savings, three times the money usually means many more working years. That trade, more spending in retirement against more years of work before it, is the real Lean-versus-Fat decision.
How the examples compare with real spending
The Bureau of Labor Statistics’ Consumer Expenditure Survey, released October 29, 2026, puts average spending for all US households (“consumer units”) in 2025 at $81,905, with average income before taxes of $110,847. The biggest pieces:
| Category (BLS, 2025 average) | Per year |
|---|---|
| Housing | $27,790 |
| Transportation | $13,492 |
| Food | $10,633 |
| Personal insurance and pensions | $10,175 |
| Healthcare | $6,470 |
| Entertainment | $4,084 |
| Apparel and services | $2,010 |
| All spending | $81,905 |
Use the average as a sense check, not a target. It mixes households of every size, age and location. And some categories, such as “personal insurance and pensions”, cover payments tied to working that may shrink or stop once you retire. Go through the list and keep only what would continue for you.
Build your own target in four steps
- Start from what you spend now. Twelve months of bank and card statements beat a guess.
- Adjust for retirement. Remove work costs such as commuting and retirement contributions. Add what work used to pay for, especially health insurance. Before Medicare, one option is coverage through the Health Insurance Marketplace, where savings depend on your income.
- Add the irregular costs. Car replacement, roof, appliances and travel come in lumps; divide each by how many years it lasts and add it to the yearly figure.
- Divide by your withdrawal rate and put the result into the FIRE calculator to see how long it takes on your savings.
Trade-offs to weigh
- A lean budget has less room to cut. Flexibility is one of the best protections against a bad market early in retirement (see sequence-of-returns risk); a budget that is already bare leaves little to trim.
- A fat budget takes longer to fund. At the same savings rate, a bigger target means more working years; the savings-rate table shows how many.
- Your spending will change. Many plans include a margin, or a lower withdrawal rate, rather than betting on one exact budget for 40 years.
Sources
- US Bureau of Labor Statistics, Consumer Expenditures in 2025, released October 29, 2026.
- HealthCare.gov, What to include as income.
