Coast FIRE: The Middle Path Nobody Talks About
The financial independence conversation is dominated by extremes. On one side, you have the hardcore FIRE adherents saving 70% of their income, biking to work in the rain, and calculating their freedom date to the month. On the other side, you have the "that's impossible on my salary" camp, who hear the FIRE message and conclude the whole thing is for software engineers and trust fund kids.
Both sides are missing the most practical path to financial independence: Coast FIRE.
What Is Coast FIRE?
Coast FIRE is the point where your existing investments — without adding another dollar — will grow to your full retirement number by a traditional retirement age. You still need to work to cover your current living expenses. But you no longer need to save for retirement.
Here's the math. Assume a 7% real return (historical average for a diversified stock portfolio, after inflation). Here's what you need invested at different ages to reach $1 million (in today's dollars) by age 65:
- Age 25: $67,000
- Age 30: $94,000
- Age 35: $131,000
- Age 40: $184,000
- Age 45: $258,000
- Age 50: $362,000
A 30-year-old with $94,000 invested can theoretically stop saving for retirement entirely, let compound growth do the work for 35 years, and retire with $1 million at 65. If your target is $2 million, double those numbers. If it's $500,000, halve them.
Notice what's not on this list: a six-figure salary. A 30-year-old earning $60,000 who manages to save $15,000 a year for six years — a 25% savings rate, aggressive but hardly ascetic — hits $94,000. That person then has the option to downshift dramatically.
The Psychology of Enough
The traditional retirement advice says: save 15% of your income, every year, for 40 years, and you'll be fine. It's fine advice, but it's psychologically brutal. It treats saving as an endless obligation, a treadmill with no finish line until you're 65.
Coast FIRE changes the conversation entirely. It gives you a number — and once you hit that number, something fundamental shifts. The retirement problem is solved. Compounding will handle the rest. Your working life from that point forward is about covering your lifestyle, not building your nest egg.
That psychological shift is more valuable than the math. People who hit their Coast number report feeling lighter, less anxious, and more willing to take career risks. They switch to jobs they actually enjoy. They go part-time. They start businesses without the existential terror of "if this fails, I'll never retire." They stop obsessing over every dollar of savings and start spending on things that actually improve their lives.
This is the middle path the FIRE purists miss. You don't have to save everything. You just have to save enough, early, and then back off.
The Risks (Because Nothing Is Free)
Coast FIRE is not a guarantee. It makes assumptions that may not hold:
Market returns aren't guaranteed. The 7% real return assumption is the US historical average. Future returns could be lower. A 5% real return instead of 7% nearly doubles the required Coast number. If you coast and the market delivers 4% real for the next 30 years — entirely possible given current valuations — you'll fall meaningfully short.
Life gets more expensive. The 25-year-old who calculates a Coast number based on spending $40,000 a year may find that at 45, with two kids and a mortgage, expenses are $80,000. Your Coast number is only valid if your retirement spending target is realistic.
Coasting means earning less. The whole point is to downshift — but earning less than you expected for 20 years changes your lifestyle, your Social Security benefit calculation, and your ability to handle financial emergencies. Coasting too early means you have less margin for error.
You might not want to work until 65. Coast FIRE assumes you'll keep working until a traditional retirement age. If at 55 you decide you're done, and you haven't saved anything since 35, you're in trouble.
How to Calculate Your Coast Number
Alistair's FIRE Calculator microtool does this math automatically, but here's the manual version:
- Estimate your retirement spending target. Be honest. Include healthcare, taxes, travel, and a buffer for the unknown.
- Multiply by 25 (the inverse of the 4% rule). That's your full retirement number.
- Work backwards using the compound interest formula. Coast Number = Retirement Number ÷ (1 + expected return)^(years until retirement).
For a 35-year-old targeting $1.25 million at 65 with a 7% return: $1,250,000 ÷ (1.07)^30 = $1,250,000 ÷ 7.61 = roughly $164,000.
That's it. If you have $164,000 invested at 35, your retirement is funded. Everything else you save from this point forward is either bringing retirement closer or increasing your spending target.
What Coast FIRE Is Really About
Coast FIRE is not really a financial strategy. It's a values exercise. It asks: once the retirement problem is solved, what do you actually want your life to look like?
Maybe the answer is: keep doing exactly what you're doing, save more, and retire earlier. That's valid. Maybe the answer is: quit the corporate job and become a teacher, a woodworker, a freelance designer. That's also valid. Maybe the answer is: stay in the high-paying job but stop caring so much about raises and promotions, because you've already won. Equally valid.
The point is that you have a choice. Coast FIRE gives you the number that unlocks that choice. What you do with it is up to you.
The Bottom Line
The loudest voices in personal finance tell you to maximize everything — income, savings rate, investment returns. Coast FIRE says something different: maximize early, then live your life.
Save hard in your 20s and early 30s. Hit your Coast number. Then give yourself permission to breathe. The math will take care of itself from there — and you'll have 30 years of your prime working life to spend however you want, without the retirement anxiety that keeps most people pinned to jobs they don't like.
That's not a compromise. It's a better version of financial independence.