Coast FIRE Explained: How Much You Need to Stop Saving Forever

There's a specific, calculable moment when you could stop contributing to your investments entirely and still retire on schedule — not because you got lucky, but because compound growth alone finishes the job. That moment has a name: Coast FIRE. It's one of the most useful numbers in the whole FIRE toolkit, and also one of the most misunderstood, so let's actually work through it.

What Is Coast FIRE?

Your Coast FIRE number is the amount you need invested today such that, left completely untouched, it will grow into your full FIRE number by a normal retirement age — say, 65 — using nothing but compound returns. Once you've hit it, you can stop adding new savings entirely and just cover your current cost of living. The investing is done. You're "coasting" the rest of the way on money that's already working.

The key distinction from regular FIRE: you're not trying to retire early with a fully funded portfolio right now. You're trying to reach financial independence on a normal timeline while getting to stop the grind of aggressive saving years, sometimes decades, sooner.

The Formula

It's a rearranged compound interest equation. If your FIRE number is FV, your expected average annual return is r, and you have n years left until traditional retirement age, your Coast FIRE number today is:

Plug in your own numbers with the Coast FIRE Calculator to skip the math entirely — but it's worth seeing it worked once by hand so the concept actually sticks.

Real Numbers

Say your FIRE number is $1,500,000 and you're using a 7% average annual return, coasting to age 65.

That's the entire appeal in one table: a 30-year-old sitting on roughly $140,000 already has $1.5M "locked in" for age 65, without saving another dollar. That's a genuinely achievable number for someone who started investing seriously in their early 20s — which is exactly why Coast FIRE tends to land hardest with people in their late 20s and 30s who've been diligent savers and are starting to feel burnt out by how aggressive their savings rate has been.

Coast FIRE vs Full FIRE vs Barista FIRE

These three get mixed up constantly, so here's the actual difference. Full FIRE means your portfolio is already large enough to cover 100% of your expenses via a safe withdrawal rate, today, with no more income needed ever. Coast FIRE means your portfolio will grow into that number on its own by a normal retirement age, but you still need income to cover today's living expenses in the meantime. Barista FIRE is a specific version of that "still need income" phase — usually part-time, lower-stress work chosen deliberately rather than a full-time career continued out of necessity.

Why It's the Underrated FIRE Variant

Full FIRE gets all the attention because the number is dramatic and the outcome is total freedom. But Coast FIRE is arguably the more livable milestone for most people, because it changes your relationship to work immediately, not eventually. Once you've hit your number, every dollar you still earn from work is entirely discretionary — you're not funding your 65-year-old self anymore, you're funding your life right now. That's a real, felt shift in how much pressure a job carries, even if you keep doing the exact same job.

It also opens doors that a pure "grind until the full number" mentality closes off: a lower-stress role, a lateral move into something more interesting but lower paid, four-day weeks, or simply not panicking every time the market dips 15%, because your number was never dependent on continuing to add new contributions during a downturn.

Is It Right for You?

Coast FIRE makes the most sense if you're currently saving aggressively and starting to feel the strain of it, if you like your career path and don't need to fully exit it, or if you value flexibility over a hard retirement date. It makes less sense if your actual goal is to stop working entirely and as early as possible — in that case, the math you want is a standard FIRE or Lean FIRE calculation instead. Either way, running the number costs you nothing and tells you something most people never actually calculate: exactly how much of the pressure you're carrying is still necessary.

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