Coast FIRE means you have invested enough that, without adding anything more, compounding alone will grow your money into a full retirement by a normal retirement age. It sits beside lean, fat and barista FIRE, the finish lines on the way to financial independence (FI): the stage at which your investments can cover your living costs and working becomes a choice. FIRE adds "retire early" to the idea.
Pictured as one distant gate, FI is so far off that it changes nothing you do this week. In fact there are several finish lines at very different distances, and the nearer ones can come decades before the last. Knowing all of them turns a far-off dream into a route you can follow.
What is Coast FIRE, and why it comes first
Coast FI: the turning point. You have invested enough that, with no further contributions, the money will grow into full retirement funding by a normal retirement age. You still work, but only to pay for today, never again to fund later.
That changes how risky a career move feels. A lower-paid job you care about, a business of your own or a few part-time years become affordable, because the future is already paid for.
How to work out your Coast FIRE number
You need 2 numbers. Your FI number is about 25 times the yearly spending you want to cover. Your Coast FIRE number is the amount that, invested today and left alone, grows into your FI number by the age you stop: your FI number divided by (1 + the yearly return), once for each year until then.
Coast FI can come early. Say you are 30, spend 30,000 a year and plan to stop at 65. Your FI number is 750,000. At 5% a year after inflation, over 35 years, about 136,000 invested today grows to that 750,000 by 65, so 136,000 is your Coast FIRE number.
The free Coast FIRE calculator runs the same sum on your own age, savings and spending. It opens on 7% a year after inflation; set a more careful rate if you prefer.
Coast FIRE vs lean FIRE vs fat FIRE vs barista FIRE
Lean FI: freedom at the level of essentials. Your investments can keep paying for a lean version of your life: housing, food, utilities and insurance, roughly the essentials you would protect first in a bad month.
It is a plain life, but from here work is optional in survival terms, and everything you earn past it buys comfort and room to breathe.
Full FI: the classic finish line. Your investments can pay for your whole current lifestyle, indefinitely. The usual estimate is about 25 times your yearly spending, the shorthand behind the well-known 4% guideline; treat it as a planning estimate rather than a promise. From here, work is a choice.
Barista FI: part-time pay fills the gap. You leave full-time work once your investments cover part of your spending, and part-time pay covers the rest. The name comes from the coffee-shop job people joke about, but any part-time work you would choose counts.
Because your investments only fund part of your life, the number is smaller. Spend 30,000 a year and keep 12,000 a year of part-time pay, and your investments need to cover 18,000: at 25 times, 450,000 instead of 750,000.
If you mean to keep some part-time pay for good, the calculator has a box for income in retirement. Put the monthly amount there, and your FI number and your Coast number drop with it.
Fat FIRE: a bigger life needs a much bigger number
Fat FI, or fat FIRE, means independence on a lifestyle bigger than the one you live now. It is a fair goal, and it costs more than most people expect, because the target grows with every bit of lifestyle you add.
If fat FI means spending twice what you spend now, you need twice the money: 50 times today's yearly spending instead of 25. For someone saving 25% of their income at 5% a year after inflation, that is about 12 more years of work after reaching full FI. Aim for half as much again instead of double, and it is about 7.
That is why fat FI is worth choosing on purpose rather than by default.
Every finish line is measured in the same unit: your yearly spending. Each bit of lifestyle you don't add moves all of them closer at once.
It is the same reason your savings rate helps twice: what you keep builds the pot, and what you don't spend shrinks the target.
Which line is yours: coast, lean, fat or barista FIRE?
Work out your spending
Every FI number is measured in what your life costs, and only tracked spending tells you that. Essentials (for lean FI) and your full lifestyle (for full FI) are two different numbers, so know both.
See where you stand against coast
Take what you have invested now, grow it at a careful rate to your retirement age, and compare it with your full FI number then. Already past it? That changes this decade's choices right away.
Close to it? The next few years of saving count for a lot, because that money has the longest time to grow.
Pick the target that changes what you do
The right finish line is the one near enough to shape this week's decisions. For early savers that is usually coast; for people further along, lean and then full. A target that feels like pure fantasy changes nothing.
Automate toward it, then mostly look away
Set the saving to happen on its own, raise it with every raise, and check your progress every quarter. FI rewards steady habits more than clever moves.
Watching a finish line decades away is hard, so we built Future Self into Wealth Mutant, our personal finance app. Future Self carries your real saving pace 10, 20 and 30 years ahead, and when your savings rate goes up, the number decades out goes up with it. Each purchase takes seconds to note, your bank is never linked, and you pay once.
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Buy — $99 onceWhat every version has in common
Every version of FI runs on the same settings: spend less than you earn, invest the difference, leave it to grow, and give it time. The names just let you count wins along the way instead of waiting for one distant gate.
And the first win comes before any of them: the month you know your numbers well enough to work out your finish lines at all. That takes a spending habit and one evening with your accounts, so start with the looking habit.
In Wealth Mutant, Future Self then shows those distances from your own entries, and the tour shows the screens around it.