What is Coast FIRE?
Coast FIRE is the moment your invested assets reach a critical mass: from here, with no further retirement contributions, compound growth would carry your portfolio to your full FIRE number by traditional retirement age if your investments earn the return you assumed. You still need to cover your current living costs. If you reach the number, you can “coast” on that assumption.
It is the most accessible milestone in the FIRE (Financial Independence, Retire Early) family because it happens far earlier than full financial independence. Reaching it in your 30s is realistic for a diligent saver, and it can give you room to take a lower-paying but more meaningful job, a career break, or start a business. It does not remove the risk: if your investments earn less than the return you assumed, you would need to start saving again.
How to calculate your Coast FIRE number
The formula has two steps:
1. Find your FIRE number — your annual retirement expenses divided by your safe withdrawal rate. At the classic 4% rule, that is expenses × 25. So $40,000/year of spending implies a $1,000,000 FIRE number.
2. Discount it back to today — divide the FIRE number by (1 + real return) raised to the number of years until retirement:
Coast FIRE number = FIRE number ÷ (1 + r)years to retirement
For a $1,000,000 FIRE number, 30 years from retirement, at a 7% real return, the Coast FIRE number is about $131,000. If you invest that much today and your investments earn exactly 7% a year after inflation, it reaches $1,000,000 by the time you retire with nothing more added.
Use a real (after-inflation) return
The single most common mistake is mixing a nominal return (say 10%) with expenses stated in today's dollars. Use a real return — about 7% is the long-run average for US stocks — so the result stays in today's purchasing power. An average is not a guarantee: in our own historical data (Shiller), a 35-year stretch of 100% US stocks reached 7% a year after inflation in only about 4 of 10 start years, and a 60/40 stock-and-bond mix in only about 1 in 20. Conservative planners use 5–6%; try 4–5% to see how much more you would need.
Coast FIRE vs Barista FIRE vs full FIRE
- Coast FIRE: you stop adding to retirement accounts and keep working to cover current expenses, relying on your portfolio growing at the return you assumed.
- Barista FIRE: semi-retire on part-time income (often for the health insurance) that covers part of your expenses, so you need a smaller portfolio. Enter part-time income above to see your lower Barista Coast FIRE number.
- Full FIRE: your portfolio covers 100% of expenses with no work required at all — the largest number of the three.
Why Coast FIRE matters
Reaching Coast FIRE flips the psychology of money. Instead of grinding to a single far-off finish line, you reach an early checkpoint after which time — not your savings rate — does the heavy lifting. The earlier you front-load investing, the lower your Coast FIRE number, because every extra year of compounding shrinks the amount you need today. That is why a 25-year-old needs far less invested to be Coast FIRE than a 45-year-old aiming at the same retirement.
Frequently asked questions
What is Coast FIRE?
The point where your current investments would grow to your full FIRE number by retirement age with no further contributions, if they earn the return you assumed. You only need to cover current expenses from here.
How do you calculate a Coast FIRE number?
FIRE number ÷ (1 + real return)years to retirement. A $1M FIRE number, 30 years out at 7% real, is about $131,000 today.
Coast FIRE vs Barista FIRE?
Coast FIRE: stop adding to retirement savings and keep working to cover expenses, if your investments grow as assumed. Barista FIRE: semi-retire on part-time income that covers part of your expenses, lowering the portfolio you need.
Can I really stop saving once I hit it?
Only if your investments earn the return you assumed, and nothing guarantees that. Returns vary a lot over 30 or more years, so keep a margin of safety, try a lower return in the calculator, and re-check the number every year or two. Coast FIRE mainly buys flexibility.