What Is Coast FIRE?
Coast FIRE is the moment you've invested enough that compound growth alone — with no further contributions — will carry your portfolio to your full FIRE number by the time you reach traditional retirement age. Once you're there, you no longer have to save for retirement; you only need to earn enough to cover your day-to-day expenses. It's one of the most liberating and least understood milestones in the whole FIRE journey.
Key takeaways
- Coast FIRE = enough invested now that growth alone hits your number by retirement.
- Formula: Coast number = FIRE number ÷ (1 + return)years left.
- The younger you are, the smaller your Coast number — time does the work.
- After coasting you can work less, switch careers, or stop saving guilt-free.
The idea behind coasting
Most FIRE strategies focus on the finish line — the day your portfolio fully covers your spending. Coast FIRE focuses on an earlier, quieter milestone: the day you can stop adding money and still arrive on time. Because compounding grows faster the longer it runs, a relatively modest sum invested early can snowball into your entire retirement number over two or three decades, untouched.
Think of it like pushing a boulder to the top of a hill. Reaching Coast FIRE is the last hard shove; after that, gravity (compounding) rolls it the rest of the way while you catch your breath.
How the Coast FIRE number is calculated
Start with your full FIRE number — your annual expenses divided by your safe withdrawal rate (25× expenses at 4%). Then discount it back to today using your expected real return and the years until retirement:
The exponent is what makes coasting so powerful. Compounding over 30+ years does an enormous amount of heavy lifting, so the amount you need today can be surprisingly small.
A worked example
Say your annual expenses are $45,000, so your full FIRE number at a 4% withdrawal rate is $1,125,000. You're 30, you plan to retire at 65, and you expect a 7% real return. That's 35 years of compounding ahead of you:
Coast number = $1,125,000 ÷ (1.07)35 ≈ $1,125,000 ÷ 10.68 ≈ $105,000.
In other words, once you have about $105,000 invested at age 30, you could theoretically never contribute another dollar and still reach $1.125M by 65. Hit that number at 25 instead, and it drops closer to $75,000. Wait until 45, and it climbs past $290,000. Time is the single biggest variable.
What coasting actually unlocks
Coast FIRE isn't really about never working again. It's about removing the pressure to save, which quietly changes your options:
- Take a job you actually like. If you only need to cover expenses, a lower-paying but more meaningful role becomes viable.
- Go part-time or freelance. You no longer need a surplus to invest, just enough to live on.
- Start a business or take a sabbatical. Your retirement is already handled in the background.
- Stop stressing. The nagging "am I saving enough?" question is answered.
Coast FIRE vs Barista FIRE vs full FIRE
These milestones stack. Most people hit them in order:
- Coast FIRE — stop investing, keep working to cover expenses; compounding finishes the job by retirement age.
- Barista FIRE — your portfolio covers part of expenses now, and part-time work covers the rest, letting you downshift sooner.
- Full FIRE — your portfolio covers everything; work is optional.
If your goal is to retire genuinely early — not at 65 — Coast FIRE is a stepping stone, not the destination. You'd either keep investing past your Coast number or lean on part-time income to bridge the gap.
The catches to watch
Coast FIRE relies on assumptions that may not hold:
- Return risk. If markets underperform your assumed rate, compounding falls short. A cushion helps.
- Lifestyle creep. If your expenses rise, your FIRE number — and therefore your Coast number — rises with them.
- Sequence risk near the end. A crash close to retirement can dent the plan; see our guide to sequence-of-returns risk.
Because of these, many people treat their calculated Coast number as a floor and keep contributing a little longer for margin.
Frequently asked questions
What is Coast FIRE?
Coast FIRE is the point where you have invested enough that compound growth alone, with no further contributions, will reach your full FIRE number by traditional retirement age. You only need to earn enough to cover current expenses.
How is the Coast FIRE number calculated?
Coast FIRE number = full FIRE number divided by (1 + real annual return) raised to the number of years until retirement. It is the amount you need invested today so growth alone reaches your target.
Can you still retire early with Coast FIRE?
Coast FIRE on its own targets a traditional retirement age. To retire early you either keep investing past your Coast number or combine it with part-time income, which is closer to Barista FIRE.
Related: What Is Barista FIRE? · The Power of Compound Interest · Coast FIRE Calculator