What Is Coast FIRE? The Point Where Your Savings Finish the Job
Coast FIRE is the moment your invested savings are big enough to grow into full retirement on their own - no new contributions needed. Here's how to find that point, and why it's a probability, not a date.
Coast FIRE is the point where the money you’ve already invested is big enough to grow into your full retirement number on its own - without another dollar of new savings. You still work, but only to cover today’s bills. The portfolio takes over the long job of getting you to retirement, and compounding does the rest.
That’s the whole idea in one sentence. The interesting part is everything that sentence quietly assumes.
What “coasting” actually means
Once you hit your coast number, you stop contributing. You don’t sell anything and you don’t retire - you just cover your living costs from your income and leave the invested balance alone. Left untouched, it keeps compounding, and over enough years a large-enough starting balance can grow into a full retirement fund by itself.
The appeal is obvious: the hardest, most disciplined stretch of saving happens early, and then the pressure comes off. You can drop to one income, take the lower-paying job you actually want, or work part-time - all without touching the plan, because the plan no longer needs your paycheck.
Coast FIRE vs. regular FIRE
Regular FIRE means you’ve saved enough to stop working altogether - your portfolio funds your entire life, today. Coast FIRE is an earlier, lower bar: you’ve saved enough that you no longer have to add money, but you still work to pay for the years between now and retirement.
So Coast FIRE isn’t “retire now.” It’s “stop saving now, and let time finish the job.” That’s why the coast number is always smaller than the full-FIRE number - the younger you are, the more growth you have left, and the less you need in the account today.
Find your own coast number
Enter your age, savings, and spending, and watch where your invested balance is big enough to coast - then see how often that plan held up across real market history.
How the number moves with age
Because coasting relies on years of growth, the same retirement target needs a very different balance today depending on when you start. Someone with four decades of compounding ahead needs far less in the account than someone with two.
| Your age today | Years of growth left | Coast number today |
|---|---|---|
| 25 | 40 | $178k |
| 30 | 35 | $227k |
| 35 | 30 | $289k |
| 40 | 25 | $369k |
| 45 | 20 | $471k |
Illustrative only - one example saver aiming for a $1.25M nest egg at 65, discounted at a 5% real return. Your own coast number depends on your target, your timeline, and the return you assume. Run your real number →
Your coast number is a probability, not a date
Here’s the catch most calculators hide. A typical coast calculator compounds your balance at one fixed return - 5%, 7%, whatever you pick - and hands you a single age. But no real portfolio grows in a straight line. Two savers can earn the exact same average return and still end up decades apart, because it matters enormously when the good and bad years arrive. A rough stretch right after you stop saving hits a smaller balance harder and leaves it less time to recover.
That’s called sequence-of-returns risk, and it’s the reason a coast number is better read as a probability than a promise. Instead of a straight line, Coastward replays your plan across more than a century of US market history (international series run shorter, and we say so) - thousands of actual sequences, crashes and recoveries kept in their true order - and reports how often it actually made it. You get the straight-line answer first, then the honest one. Here’s exactly how that works, and why the sequence of returns is the risk that matters most.
Is Coast FIRE a good idea?
It can be a genuinely good move - with two honest caveats. The first is your runway: the more years between your coast age and your retirement, the more room a bad early stretch has to recover, so coasting young is far more forgiving than coasting late. The second is your return assumption. The long US record - roughly 7% real for stocks - describes an unusually lucky century; plan to that average and you bake in survivorship luck. Coastward defaults to 5% real, deliberately below the historical mean, and lets you dial it lower. If the future turns out kinder, you’ll simply be early - the good kind of wrong.
Coast FIRE isn’t a trick or a shortcut. It’s a real plan with a specific weak point, and the point of running it against history - instead of a single-line spreadsheet - is to see that weak point clearly before you lean on it.
Frequently asked
What is Coast FIRE in simple terms?
Coast FIRE is the point where the money you've already invested is enough to grow into your full retirement number on its own - so you can stop adding new savings and just cover your living costs until you retire.
How is Coast FIRE different from regular FIRE?
Regular FIRE means you've saved enough to stop working entirely. Coast FIRE is earlier: you've saved enough that you no longer need to add money, but you still work to cover today's expenses while your portfolio compounds.
How do I calculate my Coast FIRE number?
Take your target retirement number, then discount it back to today at a realistic real return over the years until you retire. Coastward does this and then shows how often that plan actually survived real market history.
Is Coast FIRE a good idea?
It can be, if you have a long runway before retirement and a realistic return assumption. The main risk is the sequence of returns right after you stop saving - which is why it's better read as a probability than a single age.