The simplest milestone on the path to FIRE
Coast FIRE is the point where your existing investments, left untouched, will compound to your retirement target by a traditional retirement age (say 65). Once you hit it, you no longer *need* to save for retirement. You just need to cover your current expenses.
This is different from full FIRE, where you have enough to retire immediately. Coast FIRE is a waypoint — and for many people, it arrives years or even decades before full financial independence.
The math behind it
The formula is straightforward. You need to know three things:
- Your FIRE number — typically 25x your annual expenses (the 4% rule inverse)
- Your expected annual return — historically ~7% after inflation for a diversified stock portfolio
- Years until traditional retirement — how long your money has to grow
Coast FIRE Number = FIRE Number / (1 + return)^years
For example: if your FIRE number is $1.5M, you expect 7% real returns, and you're 30 years from 65:
$1,500,000 / (1.07)^35 = $139,745
If you have $140K invested at age 30, you've already hit Coast FIRE. Everything you earn from here on out only needs to cover your current lifestyle — not future retirement savings.
Why this matters for your psychology
The moment you realize you've hit Coast FIRE, something shifts. The pressure to maximize savings rate drops. You can take a lower-paying job you actually enjoy. You can work part-time. You can take a year off. The retirement math is already solved — compound interest handles the rest.
This is why Coast FIRE is the most underrated milestone in the FIRE community. It's not about stopping work. It's about the freedom that comes from knowing you don't *have* to keep saving.
When most people hit it
If you started investing in your 20s with any consistency, you might already be past Coast FIRE without knowing it. The combination of early contributions and decades of compounding is powerful.
Consider someone who invested $500/month from age 22 to 30 at 7% real returns. That's $48,000 contributed, grown to roughly $65,000. If their FIRE number is $1.5M and they're 35 years from 65, their coast number is ~$140K. They're already almost halfway there — and they only invested for 8 years.
The catch
Coast FIRE assumes you don't touch your investments. If you raid your 401k for a house down payment or cash out during a market crash, the math resets. It also assumes relatively consistent long-term returns — individual years will vary wildly.
The other catch: covering current expenses still requires income. Coast FIRE doesn't mean you can stop working entirely. It means you can stop *saving* entirely and still retire on time.
Run your own numbers
The Coast FIRE Calculator on STWLTH shows you exactly where you stand — your coast number, your current progress, and the year-by-year projection of how your portfolio grows even without contributions.