Coast FIRE is the point where your investments are large enough that, even if you never add another dollar, compound growth will carry them to your full FIRE number by the time you want to retire.
From there, you only need to earn enough to pay your current bills. You can keep working, but the pressure to save for retirement is gone. Many people use it as permission to switch to a lower-stress job, cut back hours, or take a career risk.
The Coast FIRE formula
Coast FIRE works backwards from your full FIRE number. It asks: how much would I need today for it to grow into that number by my retirement age?
Example: you spend $50,000 a year, so your FIRE number at 4% is $1,250,000. You plan to retire at 65, and you assume a 5% return after inflation. If you're 30, you have 35 years of growth ahead:
With about $227,000 invested at 30, you could stop contributing and still expect to reach $1.25 million in today's dollars by 65.
Coast FIRE numbers by age
The younger you are, the more years compounding has to work, and the smaller your Coast number:
| Your age today | Years until 65 | Coast FIRE number |
|---|---|---|
| 25 | 40 | $177,557 |
| 30 | 35 | $226,613 |
| 35 | 30 | $289,222 |
| 40 | 25 | $369,128 |
| 45 | 20 | $471,112 |
For a $1,250,000 FIRE number ($50,000 a year at 4%), retiring at 65, 5% return after inflation.
This is the clearest illustration of why early investing matters so much. The same goal needs less than half as much money invested at 30 as at 45.
What to watch out for
Use real returns, not nominal
Stocks have historically returned around 10% a year before inflation. But your FIRE number is in today's dollars, so the growth rate needs to be too. Using 10% would make the 30-year-old above think they need about $44,500 instead of $227,000.
Returns aren't guaranteed
Coast FIRE leans entirely on decades of future growth. A weak couple of decades could leave you short at 65. Building in a margin, such as coasting at a slightly lower assumed return or continuing small contributions, gives you a buffer.
Your spending may change
A FIRE number set at 28 may not match the life you want at 45, especially if you add a partner, kids or a more expensive home. Recheck your number every year or two.
Taxes and health insurance still apply
If most of your money is in pre-tax accounts, your withdrawals in retirement will be taxed. If you plan to retire before Medicare at 65, you'll pay for health insurance. Our calculator includes both in your Coast FIRE number.
Coast FIRE vs. Barista FIRE
The two are easy to mix up. With Coast FIRE, you keep working full or part time but stop contributing, and your portfolio isn't touched until retirement. With Barista FIRE, you start withdrawing from your portfolio now, and part-time income covers the rest of your spending.
Common questions
What is the difference between Coast FIRE and regular FIRE?
With regular FIRE, your portfolio can pay for your life today. With Coast FIRE, it can’t yet, but it will grow into a full FIRE number by your target retirement age without new contributions. You still need to earn enough to cover current expenses.
Should I stop investing once I hit Coast FIRE?
You can, but you don’t have to. Many people keep investing a little for a safety margin, or keep saving and use Coast FIRE as permission to take a lower-paying but more enjoyable job.
What return should I assume for Coast FIRE?
Use a return after inflation, since your FIRE number is in today’s dollars. Around 5% is a common, moderate assumption for a stock-heavy portfolio. Using a nominal return like 10% would badly overstate your progress.
This guide is for education, not personal financial or tax advice. Examples use simplified assumptions, such as a steady 5% return after inflation, that real markets won’t follow. Tax figures are for the 2026 tax year.