Coast FIRE: when your investments can carry themselves

Coast FIRE is one of the most freeing ideas in the whole financial independence toolkit. The pitch: get enough invested early, and you can stop adding to it entirely — then just coast while compounding does the rest. You still work, but only to cover today's bills. Here's how it works, and how to find your coast number.

What Coast FIRE means

Regular FIRE is about reaching a pot big enough to live off. Coast FIRE is a milestone on the way there.

You hit Coast FIRE the moment your existing investments are large enough to grow — untouched, on their own — into your full FIRE number by the time you want to retire. From that point you don't have to invest another dollar for retirement. Compounding takes it from here.

You keep working, yes. But only enough to pay for your current life — rent, food, fun. The heavy lifting for future-you is already done.

Think of it like pushing a car to the top of a long hill. The push is hard. But once you're over the crest, you can take your foot off and roll. Coast FIRE is that crest.

Why it's such a relief

The appeal isn't the maths — it's what it does to your options.

Once you've coasted past that point, the pressure comes off. You can drop to a job you actually enjoy, go part-time, take a lower-paid but meaningful role, or start something of your own without a safety net made of fear. You don't need a high income anymore. You just need to cover now.

It's financial independence's quieter cousin. Not "never work again" — more like "never work only for the money again."

How to calculate your coast number

This is where compound interest does the work. You're answering one question: how much do I need invested today so that, with no further contributions, it grows into my full FIRE number by retirement?

You need three inputs:

Your FIRE number — your annual spending × 25 (see the 4% rule).
Years until retirement — say you're 30 and want the option at 60, that's 30 years.
An assumed real return — a common, deliberately conservative assumption is around 5% per year after inflation for a stock-heavy portfolio (roughly 7% nominal minus ~2% inflation). Using a real return means your target already accounts for inflation.

The formula:

Coast number = FIRE number ÷ (1 + return)^years

A worked example

Let's use round, illustrative numbers.

Say your FIRE number is $1,000,000, you're 30, you want the option at 60 (30 years away), and you assume a 5% real return.

Growth factor = 1.05^30 ≈ 4.32
Coast number = $1,000,000 ÷ 4.32 ≈ $231,000

So with about $231,000 invested at 30, you could stop contributing entirely and — if that 5% holds on average — still land near $1,000,000 by 60. Everything you earn after that only has to cover your present-day life.

Now watch what time does. The same person at 40, with 20 years to grow, needs $1,000,000 ÷ 1.05^20 ≈ $377,000 to coast. Wait until 25, with 35 years to run, and the coast number drops to around $181,000. Start earlier and the number you need to hit is dramatically smaller. That's the single biggest lesson here.

One honest caveat: that 5% is an average assumption, not a promise. Real markets are lumpy, and sequence-of-returns risk still applies near the end. Coasting works best with a margin — and the willingness to add a bit more if markets underperform for a stretch.

Who Coast FIRE suits

It fits some situations better than others.

Young high earners who can front-load investing in their 20s and early 30s, then ease off.
People eyeing a career change — trading a stressful, well-paid job for something lighter or more meaningful.
New parents who want to cut hours without derailing retirement.
Anyone burned out who needs the income pressure to drop but isn't ready to stop working entirely.

It suits you less if you started late, if retirement is close (there's little time left for coasting to work its magic), or if your income is so variable that "just covering today" is itself a stretch. In those cases, the classic push toward a full FIRE number — with a high savings rate — is the stronger play.

Frequently asked questions

Do I stop working entirely at Coast FIRE? No — that's the whole point of the "coast." You keep working to cover current expenses. You just stop investing for retirement, because your existing pot is already on track.

Is Coast FIRE risky? It leans heavily on your assumed return holding up over decades. If markets underperform your assumption, you'll fall short. Building in a margin — a lower assumed return, or being ready to invest again — makes it far more robust.

What return should I assume? A conservative, inflation-adjusted (real) figure — around 5% for a broadly diversified, stock-heavy portfolio — is common. Using a real return means your target is already in today's money, so you're not fooled by inflation.

What's the difference between Coast FIRE and Barista FIRE? Coast FIRE is about the investments being done; you work to cover living costs. Barista FIRE is similar but usually specifically means a part-time job kept partly for benefits like health insurance. They overlap a lot.