Coast FIRE is a version of financial independence where you've saved and invested enough at a young enough age that compound growth alone, with no further contributions, will grow your portfolio to a full retirement number by a traditional retirement age. Once you hit your Coast FIRE number, you no longer need to save for retirement. You still need to work to cover today's living expenses, but the pressure to keep contributing to retirement accounts is gone, which is where the name comes from: your investments can "coast" the rest of the way on growth alone.
Most financial independence strategies focus on a single number: how much you need saved to stop working entirely. Coast FIRE asks a different question: how much do you need saved right now, at your current age, so that compound growth alone gets you to that number by a traditional retirement age like 60 or 65, even if you never contribute another dollar?
That reframing matters because it changes what "progress" looks like. Instead of measuring progress purely by your current net worth against a distant target, Coast FIRE measures whether your current savings, left alone to grow, are already on track to reach that target on their own.
This guide explains what Coast FIRE means, the formula behind it, a full worked example, how it compares to Lean, Fat, and Barista FIRE, and what the strategy does and doesn't account for.
Reaching your Coast FIRE number doesn't mean you stop working. It means you stop needing to save for retirement, because the money already invested, given enough time and an assumed rate of return, will compound into a full retirement number on its own by your target age.
You still need income to cover current living expenses, rent or mortgage, food, insurance, and everything else, so most people who hit Coast FIRE keep working. What changes is the relationship to that work: retirement contributions become optional rather than necessary, which opens the door to a lower-paying job, fewer hours, a career change, or simply less anxiety about whether you're saving "enough" every month.
The mechanism behind Coast FIRE is the same one behind all compound growth: money invested earlier has more time to grow, so it takes a smaller amount invested early to reach the same target than it would investing the same amount later. Coast FIRE is essentially the point where you've front-loaded enough of that early compounding that time can finish the job without further contributions.
The calculation works backward from your full FIRE number using the standard compound growth formula, solved for the present value needed today.
Coast FIRE Number = Full FIRE Number / (1 + Rate of Return)^Years Until Retirement
Where:
Full FIRE Number is your target retirement portfolio, typically calculated as annual expenses × 25, based on a 4% safe withdrawal rate.
Rate of Return is the assumed average annual investment growth rate, commonly modeled at 7% for a diversified stock portfolio.
Years Until Retirement is the number of years between your current age and your target traditional retirement age.
| Years Until Retirement | Full FIRE Number | Coast FIRE Number Needed Today (7% return) |
|---|---|---|
| 40 | $1,250,000 | $83,476 |
| 30 | $1,250,000 | $164,209 |
| 20 | $1,250,000 | $323,024 |
| 10 | $1,250,000 | $635,436 |
The table illustrates the core insight behind Coast FIRE: the earlier you calculate it, the smaller the number required, because there's simply more time for growth to do the work.
A 28-year-old wants to retire at age 65, a 37-year time horizon. Their target annual spending in retirement is $50,000/yr.
Full FIRE number at a 4% withdrawal rate:
$50,000 / 0.04 = $1,250,000Assuming a 7% average annual return, their Coast FIRE number is:
$1,250,000 / (1.07)^37 ≈ $102,261
Input Value Target annual spending $50,000 Full FIRE number $1,250,000 Years until retirement (65) 37 Assumed annual return 7% Coast FIRE number needed today ≈ $102,261 If this person already has roughly $102,261 invested at age 28, they don't need to contribute another dollar to retirement accounts for that money to grow into $1,250,000 by age 65, assuming a steady 7% average annual return. Anything they save beyond that point is either accelerating their timeline, increasing their eventual spending target, or building a cushion against a lower actual return.
Use the Compound Interest Calculator to try different ages, return rates, and target numbers.
| Type | What it means | Do you still work? |
|---|---|---|
| Lean FIRE | Fully retire on a minimal, tightly budgeted lifestyle, often $25,000–$40,000/yr | No |
| Fat FIRE | Fully retire with a comfortable or upscale lifestyle, often $100,000+/yr | No |
| Coast FIRE | Save enough early that compound growth alone reaches a full FIRE number by a target age, with no further contributions | Yes, full-time |
| Barista FIRE | Part-time work plus portfolio withdrawals cover expenses today, while the portfolio keeps growing | Yes, part-time |
Coast FIRE and Barista FIRE both describe a middle stage rather than a final destination, but they answer different questions. Coast FIRE is about your investment number: have you saved enough that you never need to invest another dollar? You keep working, often full-time, to cover today's expenses, and your portfolio stays untouched and compounding. Barista FIRE is about your income number today: have you reduced your required income enough that part-time work covers it, while you may be drawing on some of the portfolio's growth rather than leaving it fully untouched?
Lean FIRE and Fat FIRE describe the size of the eventual number relative to lifestyle. Coast FIRE describes a relationship between savings, time, and growth on the way to any of those numbers, whether the eventual target is a lean number or a fat one.
The single biggest input in the Coast FIRE formula isn't your savings rate or even your target spending, it's how many years of growth you have left before your target retirement age. Because growth compounds, small differences in age translate into large differences in the Coast FIRE number:
This is also why Coast FIRE calculations are highly sensitive to the assumed rate of return. A 7% assumption versus a 5% assumption produces meaningfully different numbers over a multi-decade horizon, which is worth stress-testing rather than anchoring to a single optimistic figure.
It assumes a consistent average return over decades. Real markets don't grow in a straight line. A Coast FIRE calculation done at a single point in time doesn't capture sequence-of-returns risk, the possibility of a prolonged downturn early in the growth period, or years of below-average returns that push the timeline out.
It doesn't factor in inflation unless you build it in. The formula above uses today's dollars. A target spending level and full FIRE number decades in the future should typically be adjusted for expected inflation, or modeled using a real (inflation-adjusted) rate of return instead of a nominal one.
It says nothing about current living expenses. Coast FIRE tells you when you can stop contributing to retirement accounts, not whether your current income covers your current lifestyle. Someone can be "Coast FIRE" on paper and still be living paycheck to paycheck if their day-to-day expenses aren't under control.
It doesn't model taxes or account type. Growth inside a tax-advantaged account like a 401(k) or IRA behaves differently than growth in a taxable brokerage account, and required minimum distributions or early withdrawal penalties can affect when the money is actually accessible.
Start with your target retirement age and target annual spending in retirement, then calculate your full FIRE number using the 25x rule (or your target spending divided by your chosen safe withdrawal rate). From there, work backward using an assumed rate of return to see how much needs to be invested today, then compare that to your actual current savings and investments.
A single static calculation is a reasonable starting point, but it doesn't capture how sensitive the result is to changes in your assumed return, your target retirement age, or a future decision to retire earlier or later. Calm Sea's projection tools let you enter your current savings, contribution rate, and target retirement age, then see year by year whether your portfolio is on a Coast FIRE trajectory, and how that trajectory shifts if your return assumptions, timeline, or spending target change.
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Coast FIRE means you've saved and invested enough at your current age that compound growth alone, without any further contributions, will grow your portfolio into a full retirement number by a traditional retirement age. You still work to cover today's expenses, but you no longer need to save for retirement.
Divide your full FIRE number (typically your target annual retirement spending multiplied by 25) by (1 + your assumed annual rate of return) raised to the power of the number of years until your target retirement age. For example, a $1,250,000 full FIRE number, 37 years away, at a 7% assumed return, gives a Coast FIRE number of roughly $102,261.
Coast FIRE means you've saved enough that compound growth alone will reach a full FIRE number by a target age, while you keep working, usually full-time, to cover current expenses without touching your investments. Barista FIRE means you've reduced your income needs enough that part-time work covers most expenses today, often while drawing on some of the portfolio's growth rather than leaving it fully untouched.
No. Coast FIRE means you can stop contributing to retirement accounts, not that you can stop working entirely. You still need income to cover current living expenses. What changes is that retirement savings becomes optional, which can open the door to a lower-paying job, fewer hours, or a career change.
The Coast FIRE formula divides your full FIRE number by a growth factor based on years remaining until retirement. Because that growth compounds, more years remaining means a much smaller number is needed today, while fewer years remaining requires a much larger number already in place to reach the same target.
A 7% average annual return is a commonly used assumption for a diversified stock portfolio over long time horizons, but actual returns vary significantly year to year and aren't guaranteed. It's worth calculating your Coast FIRE number under a few different return assumptions, including a more conservative one, to see how sensitive your plan is to lower long-term growth.
Calm Sea is a personal finance planning tool. Nothing in this article constitutes financial advice. All projections and calculations are illustrative estimates based on publicly available market data. Always conduct your own due diligence and consult a qualified financial adviser before making retirement decisions.
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