Most FIRE advice tells you to save 50-70% of your income and grind toward one giant number. Coast FIRE is a gentler, often more realistic milestone on the way there, and hitting it changes how it feels to go to work every day.
Coast FIRE, defined
You've reached Coast FIRE when you have enough invested that, without contributing another penny, compound growth will carry your portfolio to your full retirement number by the age you plan to retire. After that point you still need income to pay for groceries and rent, but you no longer need to save for retirement. Your future is already funded; you're just coasting to it.
How does Coast FIRE work?
Two numbers drive everything:
- Your FIRE number, the portfolio that funds your lifestyle forever. Using the 4% rule, it's your annual spending × 25 (or spending ÷ 4%).
- Your Coast FIRE number, how much you'd need invested today for growth alone to reach that FIRE number by retirement.
Because money compounds, the Coast number is a lot smaller than the full FIRE number, and the earlier you are, the smaller it gets.
What is the Coast FIRE formula?
FIRE number = annual spending ÷ withdrawal rate
Coast FIRE number = FIRE number ÷ (1 + real return)years to retirement
"Real return" just means your investment return after subtracting inflation, so every figure stays in today's dollars. Example: a 30-year-old planning to retire at 65 who wants $40,000/year needs a $1,000,000 FIRE number. At a 5% real return over 35 years, that discounts to a Coast FIRE number of about $181,000. Invest that much by 30 and, even saving nothing more, it should grow to $1M by 65.
Plug in your age, spending and savings.
Coast FIRE vs Barista, Lean and Fat FIRE
| Type | What it means | Portfolio needed |
|---|---|---|
| Coast FIRE | Stop saving; keep working to cover today's costs while investments grow. | Smallest, a fraction of full FIRE. |
| Barista FIRE | Work part-time; portfolio covers the gap your income doesn't. | Medium, less than full FIRE. |
| Lean FIRE | Fully retire on a minimalist budget. | Lower full number (small budget). |
| Full / Fat FIRE | Fully retire on a normal or generous budget. | Largest. |
See the full comparison of every FIRE type →
How to reach Coast FIRE: a 4-step plan
- Estimate your retirement spending in today's dollars (remember a paid-off home and Medicare can lower it).
- Calculate your FIRE number, spending × 25.
- Find your Coast FIRE number for your age with the Coast FIRE calculator.
- Invest aggressively until you hit it, ideally in low-cost index funds inside tax-advantaged accounts, then you're free to coast.
What are the most common Coast FIRE mistakes?
- Over-optimistic returns. Planning at 5% real is more cautious than 7%+. A small change compounds into a big difference over decades.
- Forgetting health insurance. Coast FIRE assumes you're still earning; if you go part-time, benefits matter, see Barista FIRE.
- Treating it as "done." Coast FIRE means you can stop saving, not that you must. Keep investing and you'll reach full FIRE sooner.
What the number looks like at different ages
The same $1,000,000 target, discounted back at a 5% real return to a retirement age of 65, produces very different Coast FIRE numbers depending on when you hit it:
| Age reached | Coast FIRE number | Years of compounding left |
|---|---|---|
| 25 | ≈ $142,000 | 40 |
| 35 | ≈ $231,000 | 30 |
| 45 | ≈ $377,000 | 20 |
| 55 | ≈ $614,000 | 10 |
Notice the pattern: at a 5% real return the number roughly doubles every 14 years you wait. That's the whole argument for front-loading your saving in your twenties and thirties, every dollar invested early is worth two or four invested later. The Coast FIRE by age page generates this table live from your own spending and assumptions.
What happens after you hit Coast FIRE?
Reaching your number changes the question from "how much must I save?" to "what do I actually want my weeks to look like?" Common paths:
- Same job, lighter grip. Many people change nothing at first, but negotiate harder, take real vacations, and stop tolerating bad managers, because they can afford to walk.
- Downshift. Move to a lower-stress role or four-day week and let your salary cover only current expenses. Our best jobs for Coast FIRE guide covers what makes a role coast-friendly.
- Keep saving anyway. Coast FIRE is a floor, not a ceiling. Anything you keep contributing pulls full FIRE years closer, the early retirement calculator shows exactly how many.
Whichever path you take, re-run your numbers once a year. A bad market decade, a move, or a change in planned spending can shift your coast status, catching that early costs you little; catching it late costs you years.