Milestones
Coast FIRE: When You Can Stop Contributing
Coast FIRE is the point where your existing portfolio, left completely alone, grows into your full retirement target on its own. Here is how to calculate it, why the real return assumption decides everything, and what it actually buys you.
Full FIRE asks: when can I stop working? Coast FIRE asks a smaller and often more useful question: when can I stop saving?
They are not the same milestone, and the gap between them is usually a decade or more of your life spent under very different conditions. Coast FIRE arrives far earlier, and it changes what your job is for.
The definition
You have hit Coast FIRE when your current invested balance, with no further contributions ever, will compound into your full retirement target by your retirement age.
From that day forward, every dollar you earn only has to cover the life you are living now. Your retirement is already funded — not paid out, but paid for. You are coasting.
That distinction matters. Coast FIRE does not mean you can stop working; it means you can stop working for the future. Your income requirement drops from “cover expenses plus save aggressively” to “cover expenses,” and that difference is what buys the career change, the four-day week, the sabbatical, or simply the ability to walk out of a bad job without doing arithmetic first.
The calculation
One formula, discounting your target back to today:
coast number = FIRE target / (1 + real return)^years until retirementTwo things need care.
Use your real return, not your nominal one. If your target is expressed in today’s
money — as it should be — then discounting it with a nominal rate double-counts inflation
and will tell you that you are done years before you are. At 7% nominal and 3% inflation
the real rate is 1.07 / 1.03 − 1 = 3.88%, not 4%.
Use a real FIRE target. Coasting to a target that was itself a 25× guess just moves the error. Size the target properly first — see how to calculate your FIRE number.
Worked example
Take the target from that guide: $1,394,107 in today’s money, for someone spending $50,000 a year who wants to stop at 50. At a 3.88% real return:
| Years until retirement | Age (if retiring at 50) | Coast number today |
|---|---|---|
| 30 | 20 | $444,529 |
| 25 | 25 | $537,814 |
| 20 | 30 | $650,677 |
| 15 | 35 | $787,223 |
| 10 | 40 | $952,425 |
The shape of that column is the entire lesson. A 30-year-old with $651,000 invested and a 50-year-old’s retirement plan never has to save another dollar for retirement. The same person ten years later needs $952,000 to be in the same position — $300,000 more for the same outcome, purely because they have ten fewer years of compounding to work with.
Coast FIRE gets more expensive every year you do not have it. That is the argument for front-loading savings hard in your twenties and thirties, stated in dollars.
Why the return assumption dominates
Coast FIRE is more assumption-sensitive than any other FIRE milestone, because it is a single discount applied over a very long period. Small changes compound hard.
For that same 20-years-out person with a $1,394,107 target:
| Real return assumed | Coast number |
|---|---|
| 3.0% | $771,884 |
| 3.88% (7% nominal, 3% inflation) | $650,677 |
| 5.0% | $525,424 |
A two-point swing in a number nobody can predict moves the milestone by nearly a quarter of a million dollars. Two implications follow:
- Be conservative. An optimistic coast number is not a harmless error — it is a decision to stop saving, taken years too early, discovered decades later when there is no time left to fix it.
- Coasting is not “set and forget.” Recheck annually. If markets deliver 1% real for five years, you are no longer coasting, and the correct response is to resume contributions, not to keep believing the number you calculated in a better year.
What Coast FIRE is genuinely good for
It is the first milestone that changes your actual life. Full FIRE is a distant binary. Coast FIRE is reachable in your thirties for a lot of people, and the day it arrives your relationship to work changes even if your job does not.
It converts a savings problem into an income problem. “Do I earn enough to cover my life?” is a far lower bar than “do I earn enough to cover my life plus fund my retirement?” — and it is a bar that a much wider range of work can clear.
It is a resilient state. Being coast-fired makes a layoff a disruption rather than a crisis, because the compounding continues regardless of what your employer does.
The three traps
Coasting to a target that is too small. If you coast to a 25× number and your actual horizon needs 28×, you spent a decade not saving toward a number that was never right. Get the target right before you get the coast number.
Forgetting that expenses grow. The coast number is pinned to your current spending. Have a child, buy a bigger house, upgrade your baseline permanently, and the target moves up while your untouched portfolio does not. Recalculate after every structural change to your life, not just after market moves.
Treating it as irreversible. Coasting is a state you can fall out of. Markets can underperform. Health can force early retirement. Keep the option to resume saving open, and check every year whether you are still where you thought you were.
Coast FIRE versus Barista FIRE
They are frequently confused. The cleanest distinction:
- Coast FIRE is about the portfolio: it is already large enough to finish the job alone. You still need income to cover today’s expenses, from any source.
- Barista FIRE is about the income: you have deliberately shifted to part-time or lower-stress work that covers your expenses, often precisely because you have hit Coast FIRE.
Coast is the balance-sheet condition. Barista is the lifestyle you can choose once you meet it.
The calculator shows your coast number alongside your full FIRE number, computed from the same target and your own return assumption, so you can see both milestones and the distance between them at once.