Lean FIRE vs Fat FIRE vs Coast FIRE: the numbers behind each

Lean, regular and fat FIRE differ in one number, what you spend, and Coast and Barista FIRE are not spending levels at all. The target for each, how long it takes at different savings rates, and where the labels come from.

Sep 27, 2026 · By Calcelate Team

Lean FIRE, regular FIRE and fat FIRE are the same plan at three sizes. Each one means financial independence, retire early: a portfolio big enough to pay for your life indefinitely. The only thing that changes between them is what that life costs a year, and the target follows from it by one division.

Coast FIRE and Barista FIRE are a different kind of thing. They are not spending levels but halfway points: in one you stop saving, in the other you stop working full time. You can be lean and coasting, or fat and a barista. This article puts numbers on all five, so the comparison is between targets and years rather than between labels.

What lean, regular and fat mean in dollars

The FIRE number is annual spending divided by the withdrawal rate. At 4% that is 25 times what you spend: $750,000 for a life that costs $30,000 a year, $1.5 million for $60,000, and $3.75 million for $150,000. Each column to the right is more cautious and needs more money; the same $60,000 a year needs $1,714,286 at 3.5% and $2 million at 3%.

The labels in the second column are conventions, not definitions. Nobody official draws these lines. The terms grew up in online FIRE forums and blogs, and the people who use them disagree about the edges. Lean FIRE is most often put at under $40,000 a year for a US household: Savvy Wealth describes $25,000 to $40,000 as the usual target, Financial Aha gives the same range for a single person and puts regular FIRE at $40,000 to $80,000 and fat FIRE at $100,000 or more. FIRENum sets the fat line higher, at $150,000 and up, with a “chubby” band of $80,000 to $120,000 in between. Fidelity’s definitions avoid dollar figures altogether: lean is a modest lifestyle on a small portfolio, fat is an above-average one on a large portfolio.

So when someone asks what the difference between FIRE and lean FIRE is, the honest answer is a row in that table, not a category. Pick the spending you actually expect, read across, and the label is whatever your forum calls it. Outside the US, or in an expensive city, the same words describe very different sums.

Where the 4% comes from, and why it is American

The withdrawal rate is the assumption that does the most work, and it is American. William Bengen tested it against US stock, bond and inflation data in the Journal of Financial Planning in 1994. Withdrawing 4% in the first year and raising the amount with inflation afterwards never exhausted a portfolio in under 33 years; 3% never did in under 50. The Trinity study in the AAII Journal in 1998 reached a similar conclusion for US portfolios, calling 3% and 4% “extremely unlikely to exhaust any portfolio of stocks and bonds” over the payout periods it tested, the longest of which was 30 years.

Two consequences for anyone retiring early. First, 30 years is short if you stop at 40, which is why the 3.5% and 3% columns exist. Second, it is US market history. Nothing guarantees that another country’s markets, or the next 30 years anywhere, behave the same way, so treat 4% as a rough guide rather than a law. There is no separate “fat FIRE 4% rule”: it is the same 25 times, and people with more room to cut back in a bad year can live with it more easily than people already spending at the lean end.

How long each one takes

Every number here assumes a 7% annual return and 3% inflation, which is about 3.9% a year after inflation, the same defaults as the FIRE calculator, and that you keep spending in retirement what you spent while working.

The savings rate decides almost everything. Save 20% of your take-home pay and it takes 42 years from zero; save half and it takes 18; save 70% and it takes 10. Starting from nothing, your income does not appear in that sum at all, because a higher income raises the savings and the target together. What matters is the share you keep, and that share is where lean and fat actually differ.

Look at the ages. The lean household earning $60,000 and spending half of it gets there at 48. The same lifestyle on a $100,000 salary gets there at 44, because the same modest life now leaves 60% of the pay untouched. The regular household, on that same $100,000 but spending $60,000, waits until 54.

The fat household reaches $3 million at 47, a year before the lean one reaches $750,000. That is not because fat FIRE is easier. It is because $250,000 after tax lets it spend $120,000 and still save more than half. Fat FIRE is a plan for high incomes; on an ordinary salary, the spending that makes it fat is also the spending that makes the savings rate too low to finish.

Coast FIRE: stop saving, not working

Coast FIRE is the point at which the money already invested will grow into your FIRE number by a chosen age with no further contributions. You keep working, but only to pay for the life you live now; retirement saving is done.

The calculator does not show this number directly, so it is derived here with ordinary compound growth: the FIRE number divided by (1 + real return) raised to the years left. The table takes regular FIRE at $60,000 a year, a target of $1.5 million, and the same 3.9% real return.

At 35, $578,665 invested is enough to coast to $1.5 million by 60: 39% of the target, and you never add another dollar. At 25, coasting to 65 takes $326,760. At 45 it takes $700,100. The later you start coasting, the less time compounding has, and the closer the coast number gets to the target itself.

Does Coast FIRE actually work? The arithmetic does, but it leans entirely on the return assumption over 20 or 30 years with nothing going in, which is the part of the plan with the least room for error. A decade of weak markets does not change your FIRE number, it changes the date. The usual safeguard is to treat the coast number as a floor rather than a finish line and keep saving something when you can.

Barista FIRE: work a little, need less

Barista FIRE is leaving full-time work before the portfolio can carry everything, and letting part-time income cover the gap. The portfolio then has to pay only for the difference, so the target shrinks by 25 times every dollar of part-time pay. Fidelity describes it as semi-retirement with a part-time job to fill gaps in the budget, possibly with benefits such as health cover, which is mostly an American reason to keep a job.

Take someone spending $60,000 a year and saving $40,000 from zero. Full FIRE needs $1.5 million and arrives in 24 years. With $20,000 a year of part-time work, the portfolio covers $40,000, the target falls to $1 million, and the switch comes in 18 years, at 48 instead of 54.

That makes the difference between lean FIRE and Barista FIRE plain. Lean FIRE shrinks the target by spending less, forever. Barista FIRE shrinks it by earning a bit, for as long as the earning lasts. It needs a plan for the day the part-time work stops, whether that is a state pension arriving or a few more years of growth, because on that day the portfolio has to cover the full $60,000.

Coast and Barista are easy to mix up, and the difference is what you keep doing. Coast FIRE means you stop saving but still earn everything you spend, until the target age. Barista FIRE means you stop working full time and let a smaller job pay part of the bills while the portfolio pays the rest.

What the numbers leave out

Everything here is in today’s money and before tax on withdrawals. It ignores state pensions and Social Security, which lower the target once they start, and the cost of healthcare before they do. It assumes spending stays flat for decades. Treat each table as the shape of the problem, then put your own spending, savings and starting balance into the calculator and rerun it every year.