Coast FIRE
The milestone where you can stop contributing and still retire on time.
What Coast FIRE is
Coast FIRE means you've saved enough early that compound growth alone — with no further contributions — grows into a full retirement number by a traditional retirement age. Once you hit that point you only need to earn enough to cover your current living expenses. The retirement savings coast.
It is not early retirement. You keep working; what changes is that you stop having to save, which is a different and much earlier milestone than FIRE.
Why it's reachable when FIRE isn't
Full FIRE asks you to fund every year of retirement. Coast FIRE asks you to fund only the first stretch and let time do the rest — and time is doing most of the work either way. Money invested at 25 has forty years to compound; the same dollar at 45 has twenty.
That's why the number falls so sharply the earlier you hit it, and why it's the milestone worth aiming at if a 50% savings rate was never going to happen.
Working out your number
Start from the retirement number you'd need at your target age, then discount it back to today at your expected real return. What you get is the balance that, left completely alone, arrives at that number on time.
The compound interest calculator does this directly: set contributions to zero after the year you'd stop, and see whether the balance still lands where it needs to. Its advanced option exists for exactly this — changing the contribution partway through the timeline.
What it actually buys you
Optionality, mostly. Hitting Coast FIRE means a lower-paying job you'd rather do, a career break, or a period of one income instead of two stops threatening the retirement plan — the plan is already funded.
It's also a hedge against the thing that derails most retirement saving: a decade where life costs more than expected. Front-loading the saving means that decade costs you flexibility rather than the whole plan.