What Coast FIRE Actually Means
Coast FIRE is the point where you've invested enough that compound growth alone will grow your portfolio to your retirement target by your planned retirement age — without contributing another dollar. From that point forward, you only need to earn enough to cover your current living expenses.
Example: you're 32 with $200,000 invested. At a 7% real return, that $200,000 grows to ~$1.5 million by age 65 without any additional contributions. If $1.5 million is your target, you've hit Coast FIRE. You don't have to stop working or saving — but you don't have to maximize contributions anymore.
This opens up career flexibility that traditional FIRE doesn't. You could take a lower-paying job you love, go part-time, start a business, or take a sabbatical — because the retirement math works without aggressive saving.
The Coast FIRE Formula
Your Coast FIRE number = Target Retirement Portfolio ÷ (1 + real return rate)^(years until retirement). That's it.
If your target is $1.5 million, you plan to retire at 65, you're currently 35, and you assume 7% real returns: $1,500,000 ÷ (1.07)^30 = $197,000. If you have $197,000 invested today, you're Coast FIRE.
The three variables that matter most: (1) your target portfolio size (driven by your desired retirement spending), (2) years until retirement (time is the biggest lever), and (3) assumed real return rate (7% is aggressive but historically reasonable for equity-heavy portfolios).
Coast FIRE vs Other FIRE Variants
Traditional FIRE requires 25x your annual expenses invested (the inverse of the 4% Rule). For someone spending $50,000/year, that's $1.25 million. Lean FIRE targets a more frugal lifestyle (~$40,000/year = $1 million). Fat FIRE aims for a generous lifestyle ($100,000+/year = $2.5 million+).
Coast FIRE is fundamentally different because it's not about reaching the finish line today — it's about reaching the point where you're mathematically guaranteed to reach it later. This makes it achievable much earlier in life.
Barista FIRE is the closest cousin — it means you've hit a partial FIRE number and work a low-stress job (the stereotypical example: barista) for healthcare and basic expenses. Coast FIRE is similar but specifically about investment growth covering retirement.
Risks and Reality Checks
The big risk: your assumed return rate might not materialize. If you assume 7% real returns but get 5%, you'll be short. This is why we recommend running the Coast FIRE calculation at multiple return rates (5%, 6%, 7%) to see the sensitivity.
Inflation is already accounted for if you're using real (inflation-adjusted) returns. But lifestyle inflation isn't — if your target spending increases over time, your Coast FIRE number increases too.
The psychological challenge is real: once you hit Coast FIRE, it's tempting to stop saving entirely. Having a buffer above the minimum Coast number gives you resilience against market downturns.
📌 Key Takeaways
- 1Coast FIRE = enough invested that compound growth alone funds your retirement
- 2The formula is simple: Target ÷ (1 + return)^years = Coast FIRE number
- 3It's achievable much earlier than traditional FIRE because time does the heavy lifting
- 4Run the calculation at multiple return rates (5-7%) to understand the range
- 5Coast FIRE opens career flexibility without sacrificing retirement security
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