What Is Coast FIRE — and How Do I Know If I've Hit It?
What Coast FIRE actually means
FIRE stands for Financial Independence, Retire Early. Coast FIRE is a specific milestone on that path. You reach it when your invested balance is large enough that, left completely untouched, it will compound up to your full retirement target by the age you plan to retire — without any further contributions.
The word 'coast' is literal. Picture pedaling a bike hard up to speed, then taking your feet off the pedals and gliding. Once you are coasting, your existing momentum carries you the rest of the way. In financial terms, compounding is the momentum: after you have invested enough early on, decades of growth do the remaining work while you simply cover today's expenses with today's income.
Coast FIRE vs. full FIRE vs. Barista FIRE
These terms get mixed up, so it helps to separate them. Full FIRE means your portfolio is already large enough to fund your living expenses right now — you could stop working entirely. Coast FIRE is earlier and easier: your portfolio isn't big enough to live on yet, but it is big enough to grow into a full nest egg on its own, so you only need to earn enough to pay current bills. Barista FIRE is a close cousin — working part-time (the classic example being a job with health benefits) to cover expenses while your investments coast.
The practical difference is freedom of choice. A Coast-FIRE saver can downshift to lower-paying but more meaningful work, take a career break, or start a business, because they are no longer racing to fund retirement — that account is already on autopilot. They just need to not withdraw from it and to cover their monthly costs some other way.
How to calculate your Coast FIRE number
The math is a compounding calculation run in reverse. Start with the nest egg you will need at your retirement age, then discount it back to today at your expected annual return. The result is the amount you need invested now for compounding alone to reach the goal. The formula is:
Coast FIRE number = Target retirement nest egg ÷ (1 + real return)years until retirement
A common way to set the target nest egg is the 4% rule of thumb: multiply your desired annual retirement spending by 25. So if you want $40,000 a year in today's dollars, your target is roughly $1,000,000. The exact figure is sensitive to your assumptions — a percentage point of return or a few years of horizon moves it a lot — so it is worth calculating precisely. Our Coast FIRE number calculator does the discounting for you and shows the balance you need at your current age.
A worked example: are you already coasting?
Say you are 35, want to retire at 65 (a 30-year runway), and expect a 5% real return after inflation. Your target nest egg is $1,000,000 in today's dollars. Discounting that back 30 years at 5% gives a Coast FIRE number of about $231,000. In other words, if you have roughly $231,000 invested at age 35, you could stop contributing entirely and still expect to reach $1,000,000 by 65 — purely from compounding.
| Current age | Years to 65 | Coast FIRE number (for a $1M goal, 5% real) |
|---|---|---|
| 25 | 40 | ~$142,000 |
| 35 | 30 | ~$231,000 |
| 45 | 20 | ~$377,000 |
| 55 | 10 | ~$614,000 |
Notice how much smaller the number is when you are young — that is compounding rewarding early savers. The 25-year-old needs only about $142,000 invested to coast to the same $1,000,000, because their money has 40 years to grow. This is the single strongest argument for front-loading your investing in your twenties and thirties.
What to do once you've hit Coast FIRE
Reaching Coast FIRE does not mean you must change anything — but it means you can. Your options open up: keep contributing and reach full FIRE sooner; stop contributing and redirect that money to living better today; or downshift to work you enjoy more even if it pays less. The one rule is that the coasting portfolio stays invested and untouched, so its compounding assumption holds.
It also helps to know how much sooner full independence arrives if you keep saving. Your savings rate — the share of income you invest — is the biggest lever on your timeline to full FIRE. To see how many years different savings rates shave off your path, run your income and spending through our savings rate to financial independence calculator. Many people discover that even after coasting, a modest continued savings rate pulls their full-independence date years closer.
The assumptions that make or break your number
Coast FIRE is only as reliable as its inputs, so treat the number as a plan to revisit, not a guarantee. The two most sensitive assumptions are your real return and your retirement age. Use a conservative real return (many planners use 4–5% after inflation for a balanced portfolio) so you are not counting on a rosy market. Recheck your number every few years, because your target spending, your timeline, and market conditions all drift. And remember these figures are in today's dollars — using a real (after-inflation) return keeps the whole calculation in purchasing power you can actually recognize.
Frequently asked questions
What is the difference between Coast FIRE and regular FIRE?
Regular (full) FIRE means your portfolio is already large enough to live on, so you could stop working now. Coast FIRE is an earlier milestone: your portfolio isn't big enough to live on yet, but it is big enough to grow into a full retirement nest egg on its own without further contributions. A Coast-FIRE saver still works to cover current expenses, but no longer needs to save for retirement.
How do I calculate my Coast FIRE number?
Take the nest egg you'll need at retirement (a common estimate is 25 times your desired annual spending) and discount it back to today at your expected real return: target ÷ (1 + real return)^years to retirement. The result is how much you need invested now for compounding alone to reach the goal. A Coast FIRE calculator does this discounting automatically for your age and assumptions.
Can I stop saving completely once I hit Coast FIRE?
For retirement, yes — that is the whole idea: your existing balance is projected to reach your goal on its own, so you only need to earn enough to cover current living costs. But this assumes you leave the coasting portfolio invested and untouched, and that your return and retirement-age assumptions hold. Many people keep saving a little to build a safety margin or reach full FIRE sooner.
What return should I assume for Coast FIRE?
Use a conservative real (after-inflation) return so you're not depending on a perfect market — many planners use 4–5% for a balanced portfolio, or up to about 7% real for a stock-heavy one based on long-run U.S. history. Because the number is highly sensitive to this assumption, it is safer to under-assume your return and recheck the figure every few years as conditions change.
Does Coast FIRE account for inflation?
It does when you use a real (after-inflation) return and express your target in today's dollars, which is the standard approach. That keeps the entire calculation in purchasing power you can recognize, so a $1,000,000 goal means $1,000,000 of today's buying power. If you instead use a nominal return, you must also inflate your target, which is easier to get wrong — real terms keep it simple.
Is Coast FIRE realistic on an average income?
It can be, especially if you start young, because the required number is far smaller with a longer runway — a 25-year-old needs roughly a third of what a 45-year-old needs for the same goal. The keys are starting early, keeping investment fees low, and staying invested through downturns. Even reaching Coast FIRE in your thirties or forties gives you meaningful freedom to change how and how much you work.
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