Fat FIRE Calculator

How Fat FIRE works

Fat FIRE means reaching financial independence with a generous budget: enough for travel, hobbies, helping family and a cushion for surprises, not just the essentials. Because spending is higher, the target is much bigger, and getting there early usually takes a high income and a high savings rate.

What counts as fat?

In the US, people often call a budget fat if it's over roughly $100,000 a year, and some set the bar much higher. Like "lean", it's an informal label from FIRE communities, not a rule, and it depends heavily on where you live and who you support. A family in an expensive city may need $120,000 a year just to live comfortably, while the same amount goes much further elsewhere. Lean FIRE vs Fat FIRE compares the two approaches.

A worked example

Spending $120,000 a year at a 4% withdrawal rate gives a Fat FIRE number of $3,000,000. Starting at 32 with $400,000 invested and $4,000 a month going in, at a 7% yearly return and 2.5% inflation (a 4.39% real return), you'd reach it in 23 years 4 months, at age 55.

Big targets are sensitive to small changes. At a 3.5% withdrawal rate, the number rises to $3,428,571 and takes 25 years 7 months (age 57). At 3%, you'd need $4,000,000, which this saver doesn't reach before 60. In the other direction, spending $100,000 instead lowers the 4% target to $2,500,000, reached in 20 years 3 months (age 52), while saving $5,000 a month instead of $4,000 gets to the full $3,000,000 in 20 years 11 months (age 52).

Why aim for a bigger budget?

A generous budget buys margin. If markets fall early in retirement, you can cut back on travel and extras without touching the essentials, something a lean plan can't easily do. That ability to spend less in bad years is one of the best protections against running out of money, and it helps a fat plan get through a rough start that would strain a tighter one.

The trade-offs

The cost is time. At a 4% rate, every extra $10,000 a year of spending adds $250,000 to the target, which can mean several more years of full-time work. That's a real price if work is what you want to leave. Taxes also weigh more at higher spending: withdrawals from tax-deferred accounts such as a 401(k) or traditional IRA count as income, so the spending you enter should include the tax you expect to pay. In the US, budget for health insurance until Medicare starts at 65 as well.

Some people take a middle path: reach Coast FIRE or Barista FIRE first, then keep earning on their own terms while the portfolio grows toward the fat number. With the example numbers, you'd reach Coast FIRE after 13 years 11 months, at 45, more than nine years before full Fat FIRE. The Coast FIRE calculator finds that month for you, and the Barista FIRE calculator shows how part-time income lowers what you need.

More tools and reading

For a budget closer to average, use the FIRE number calculator. The Coast FIRE number page shows how much you need invested at each age, and the methodology page explains every formula and default. For background, read what is FIRE and the 4% rule explained.