Coast FIRE

Coast FIRE: the moment you can stop saving and let compounding finish the job

Dylan 7 July 2026 6 min read

There is a strange, quiet moment in a FIRE plan when you run the numbers and realise you might already be done saving. Not done working, not suddenly rich, just done adding to the pot. If the money you have already invested will grow on its own into your full retirement number by the time you are in your sixties, you never have to put in another krone. You only have to leave it alone. That is Coast FIRE: the point where compounding, with no more help from you, finishes the job by your target age.

What Coast FIRE actually means

Coast FIRE is a threshold, not a finish line. You reach it the day the money already in your investments will, on its own, compound up to your full FIRE number by your target retirement age, with zero further contributions. From then on, the saving job is done. You keep working, but only to cover this month's rent and groceries, not to feed the pot. Past your Coast number, the pot does the saving for you, and your job just has to cover today.

The "keep working" part is the whole trick, so it is worth being precise about it. You are not retired. You still earn and you still pay your way. What changes is that none of that income has to go into investments anymore, because the future is already funded by the growth on what you hold. Everything you make above today's costs is simply yours.

Finding your Coast number

To find your Coast number you work backwards. Start from the full FIRE number you will need at your target age, then discount it back to today at an assumed real return, the growth rate after inflation. The further away your target age, the more years compounding has to run, so the smaller the slice you need invested right now. Here is the rough shape of it, using a 5 percent real return, which is only an assumption:

Years to your target age	Roughly what fraction of your FIRE number you need invested today
30 years	about 23%
20 years	about 38%
15 years	about 48%
10 years	about 61%

Assumes a 5 percent real return, which is an assumption, not a promise. Fewer years, or a lower return, means you need more today.

Read a row like this: at twenty years out, having roughly 38% of your eventual number already invested means that, on this assumption, you could stop adding to it today and still coast to the full figure by your target age. Nudge the return down, or shorten the runway, and every fraction in the table climbs. That is why the number is a feel for where you stand, not a line to bank your life on.

Why it is freeing, and the catch

The freeing part is real. Hitting your Coast number can mean downshifting decades before a normal retirement: going part-time, moving to work you actually like, taking the lower-paid job that fits your life, because that income now only has to cover today, not build tomorrow. The quiet pressure to out-earn and out-save, the thing that makes so many diligent savers miserable, comes off. You have already done the hard part.

The catch is that Coast FIRE leans its whole weight on one assumption: that the market delivers something close to that long-run return over your remaining decades. It might not. A weak decade early on, or a bad run of returns right as you stop contributing, what people call sequence-of-returns risk, can leave the pot short of where the tidy discount table promised, and you are no longer saving to make up the difference. You also still have to cover today's costs the entire time, so this is a change in what your job is for, not an escape from having one. Coast FIRE trades certainty for time. It can be a wonderful trade, as long as you go in knowing which side of it you are standing on.

Past your Coast number, the pot does the saving for you, and your job just has to cover today.

Runway's money-over-time chart showing a pot growing toward a goal line — Watch the pot grow toward your number, year by year.

Find the age you can stop saving

Runway has a Coast solver that finds the age you can stop saving from your real figures, not a round-number guess, and shows it against your full number. It launches on the App Store on 25 August 2026, and the beta is open now.

Runway has a Coast solver that finds the age you can stop saving from your real figures, not a round-number guess, and shows it against your full number. Your freedom age is free, forever.

Try the beta on TestFlight Download free on the App Store

Frequently asked

What is Coast FIRE?+

Coast FIRE is the point where the money you have already invested will, on its own, compound up to your full retirement number by your target age, with no further contributions. Once you are past it, you can stop saving and keep working only to cover today's spending, while the pot grows into your future number by itself.

How do I calculate my Coast FIRE number?+

You work backwards. Take the full FIRE number you will need at your target age and discount it back to today at an assumed real return, the growth rate after inflation. That discounted figure is your Coast number: the amount that, left alone, should grow into the full number by then. The further off your target age, the smaller the slice you need invested now. Change the assumed return and the number moves, so treat it as a feel for it, not a promise.

Is Coast FIRE risky?+

It carries a specific risk. Coast FIRE leans its whole weight on the market delivering something like its assumed long-run return over your remaining decades. A weak decade, or a bad run of returns just after you stop contributing, can leave the pot short of where the tidy math said it would be, and you are no longer saving to close the gap. You also still have to cover today's costs the whole time. It can be a great trade, as long as you know it is one.

What is the difference between Coast FIRE and Barista FIRE?+

They overlap, but they are not the same. Coast FIRE is about the pot: you have invested enough that you can stop saving and let it grow into your full number on its own. Barista FIRE is about income: you semi-retire and keep some part-time work to cover your costs, often for the benefits, so you do not have to touch the pot yet. You can be both at once. More on the half-retired version in Barista FIRE.

Written by Dylan, maker of Runway

Italian, in Norway about eight years, building the cross-border FIRE planner that did not exist for someone like me. Runway runs entirely on your iPhone. It is an educational planning tool, not financial or tax advice.

The takeaway: Coast FIRE is the day compounding can finish the job without you. It can buy you decades of freedom, as long as the returns it quietly assumes actually turn up.