What is Coast FIRE? How to calculate your number
August 2026 · 5 min read
Coast FIRE is probably the most psychologically satisfying milestone in the FIRE world. It's the point where you have enough invested that compound growth alone will carry you to a full retirement — without saving another dollar.
You still work. You still earn money. But every paycheck goes to living your life right now, because future-you is already taken care of.
The formula
Your Coast FIRE number depends on three things:
- Your target retirement number (usually 25× annual expenses)
- Your expected real return (after inflation — typically 7%)
- How many years until you plan to retire
The formula is:
You're basically asking: "What amount, growing at 7% per year for N years, will reach my retirement target?"
Real examples
Let's say you want $1M by age 65 (that's $40k/year at a 4% withdrawal rate). Assuming 7% real returns:
| Your age | Years to 65 | Coast number |
|---|---|---|
| 25 | 40 | $66,780 |
| 30 | 35 | $93,660 |
| 35 | 30 | $131,370 |
| 40 | 25 | $184,250 |
| 45 | 20 | $258,420 |
| 50 | 15 | $362,450 |
Look at the 25-year-old row. If you have $67k invested at 25 and never save another penny for retirement, you'll still have $1M by 65. That's the power of compounding over decades.
Why Coast FIRE matters
Most people won't fully retire at 35. That's fine. Coast FIRE gives you a different kind of freedom:
- Take a lower-paying job you actually enjoy
- Go part-time without worrying about your future
- Start a business without the pressure to maximize income
- Take a year off to travel — your portfolio keeps growing without you
It's not about quitting work entirely. It's about removing the obligation to earn for your future self.
The catch
Coast FIRE assumes a few things that might not hold:
- 7% real returns aren't guaranteed. The next 30 years might look different from the last 30. Lower returns mean your coast number is actually higher.
- Your expenses might change. Kids, healthcare, lifestyle inflation — $40k/year at 65 might not cut it.
- You still need to cover today's expenses. Coast FIRE doesn't help with rent this month. You still need income; you just don't need to save any of it.
Calculate yours
You can run your own numbers with the retirement calculator — it shows your Coast FIRE number alongside all the other strategies. Adjust your expected return and retirement age to see how sensitive the number is to your assumptions.