Lean vs Fat FIRE Calculator
Compare the Lean FIRE and Fat FIRE nest eggs side by side — how much more you must save for a comfortable versus a frugal early retirement.
How it works
FIRE number = annual expenses ÷ SWR · Extra = Fat number − Lean number
Lean FIRE targets a frugal early retirement on minimal expenses, while Fat FIRE aims for a comfortable, spend-freely lifestyle. Because the required nest egg is just annual spending divided by the withdrawal rate, the two numbers scale directly with your spending. This calculator shows the price of a bigger lifestyle in nest-egg terms.
Worked example
At a 4% withdrawal rate, $30,000 of lean spending needs $750,000, while $100,000 of fat spending needs $2,500,000 — 3.33× as much, an extra $1,750,000 to retire in comfort rather than frugality.
Frequently asked questions
What counts as Lean vs Fat FIRE?
There is no official line, but Lean FIRE usually means living on a tight budget (often under about $40,000/year), while Fat FIRE means retiring with a generous budget (often $100,000+/year) and few sacrifices. Both use the same math — only the spending assumption changes.
Why is the Fat FIRE number so much larger?
Because the nest egg is a fixed multiple of annual spending (25× at a 4% rate), doubling your target lifestyle doubles the savings you need. Small differences in yearly spending become large differences in the portfolio.
Which one should I aim for?
That depends on how much you value time versus lifestyle. Lean FIRE gets you out of work sooner; Fat FIRE takes longer to fund but leaves more room in the budget. Many people target a level in between, sometimes called Chubby FIRE.
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Educational estimate, not financial advice.