Coast FIRE: The Lazy Path to FI

You May Already Be Done Saving for Retirement

Not done with work, necessarily. But done with the hard part — the aggressive saving, the maxing everything, the spreadsheet guilt every time you buy a slightly fancy dinner.

Coast FIRE is the idea that you’ve accumulated enough invested assets that compound growth alone will carry you to your FI number by traditional retirement age. No additional contributions required. Your money is already doing the job. You just have to not touch it.

That’s it. That’s the whole thing.

If that sounds suspiciously like “give up and coast,” well — yes. Intentionally. And there’s real math behind it.

The Math That Makes This Work

Here’s the concrete version. Say you’re 35 years old and you’ve got $300,000 invested in index funds. You’re not planning to touch it for 30 years.

At 7% real annual return (that’s inflation-adjusted, roughly the long-run average for a diversified equity portfolio), $300k compounds like this:

$300,000 × (1.07)^30 = $2,283,677

Wait, that’s over $2.2 million in today’s dollars. If your FIRE number is $1.5M (spending $60k/year at a 4% withdrawal rate), you blew past it by age 65 without adding a single additional dollar.

Now do it with $200k at 35:

$200,000 × (1.07)^30 = $1,522,451

Still more than $1.5M. You hit coast FIRE at $200k with 30 years to run.

The coast FIRE number formula is:

Coast FI Number = FI Target / (1 + growth rate)^years_to_retirement

So if your FI target is $1.5M, you want to retire at 65, and you’re currently 35:

Coast Number = $1,500,000 / (1.07)^30 = ~$197,000

That’s your coast number. If you have ~$197k invested today at age 35, you can stop contributing to retirement accounts and still hit $1.5M by 65.

Hit $300k at 35? You’ve got a $783k buffer above your $1.5M FI goal at age 65. You’re deep in coast territory. The math is working for you while you sleep.

What “Coasting” Actually Means Day-to-Day

Once you’ve hit your coast number, the math says your retirement is taken care of. Which means the only thing your job needs to do now is cover your living expenses.

That’s a fundamentally different constraint than “save 25% of income and max every account.” You no longer need a high-paying, high-stress job to reach FI. You just need enough income to pay rent, buy food, and keep the lights on.

This opens up options that didn’t exist before:

• Take the lower-stress job that pays $30k less
• Go part-time or contract
• Move to a lower cost-of-living city where your skills pay the same but rent is half
• Take the career risk you’ve been avoiding because you were afraid of income disruption
• Start the business, knowing the downside is “I fail and get a normal job again”

The coast phase isn’t early retirement. It’s optional intensity. You still work — but you work because you want the structure, the social contact, the income, or the health insurance. Not because your retirement depends on it.

That psychological shift is the underrated part of coast FIRE.

Why This Hits Different Psychologically

Standard FIRE math is ruthless. Every dollar spent is a dollar not invested is a fraction of a percent off your withdrawal rate is a few more weeks you’ll spend in an office. The compounding guilt is real.

Coast FIRE breaks that loop. Once you’ve hit your number, the daily spending anxiety basically evaporates. You still care about not being reckless with money — but blowing $800 on a vacation doesn’t cost you six months of early retirement anymore. It just costs $800.

The anxiety profile of early FIRE is also weird. Most people who are actually pursuing FIRE are not worried about the retire-at-45 plan. They’re worried about what happens if the market crashes at 44. Or if they miscalculated their spending. Or if healthcare ruins everything. The sequence-of-returns risk alone is enough to keep you up at night.

Coast FIRE sidesteps most of this. You’re not withdrawing early. You’re letting the portfolio ride for 30 years and only touching it at 65. The sequence risk you’re actually worried about is the last few years before a normal retirement — which everyone faces regardless of FIRE strategy.

You’re not more exposed. You’re actually less exposed than someone who retires at 45 and has to survive a 50-year withdrawal sequence.

Why Most Coast FIRE People Keep Saving Anyway

Here’s the honest thing: most people who hit their coast number don’t actually stop contributing.

A few reasons:

The assumptions are conservative estimates. 7% real return is a long-run historical average, not a guarantee. Some people use 5% or 6% to build in a buffer. That bumps your required coast number up significantly. At 5% real growth over 30 years, that $200k becomes $865k, not $1.5M. You’d need about $346k at 35 to coast to $1.5M.

Earlier full FIRE is more appealing than later. Extra contributions aren’t wasted — they shrink the gap between coast and lean FIRE, which is the gap between “I work because I have to cover expenses” and “I work because I feel like it.” Every additional $100k invested accelerates your full FIRE date.

Optionality compounds too. Having $600k at 40 instead of $200k at 35 means you could retire at 55 instead of 65. That’s ten extra years of full freedom. That’s not nothing.

Healthcare is unsolved. In the coast phase you still need employer-sponsored health insurance or enough income to buy it on the ACA marketplace. That constraint alone can keep you in a “real” job longer than the math says you need to.

None of this means you shouldn’t treat hitting your coast number as a real milestone. It is. But treat it as “I’ve unlocked the easy mode” rather than “I can stop thinking about money entirely.”

Running the Numbers for Yourself

There are several calculators that handle this well. The most popular ones:

• Engaging Data’s Coast FI calculator — clean interface, lets you set your FI target, current age, and assumed return rate
• cFIREsim — more sophisticated, handles sequence-of-returns simulations
• ProjectionLab — paid tool but handles the full picture including coast scenarios

The key inputs you need:

Plug in your numbers and find out where you stand. You might be closer than you think. A 38-year-old with $250k who targets $1.2M for retirement is already in coast territory at 5% growth with 27 years to run. Run the actual calculation before you assume you’re not there.

The Assumptions Behind Coast FIRE (And Where They Break)

This all runs on a few key assumptions. Know what they are.

7% real return is a long-run average. The US stock market has done roughly 7% real return over long periods. But long periods have included some brutal decades. The 2000s lost a decade for US equities in real terms. A 30-year horizon smooths most of this out — but you need the full 30 years. Rage-quitting your job at 40 and spending down your coast portfolio early kills this strategy.

Sequence-of-returns risk is lower here, but still present. The traditional FIRE sequence risk — retiring early and hitting a bad decade immediately — is dramatically reduced in coast FIRE because you’re not withdrawing during the coast phase. But the years right before and after your actual retirement age still matter. A bad decade from 60 to 70 hits harder than one from 35 to 45 when you’re still working and not withdrawing.

Health insurance is the practical ceiling. This is the real constraint during the coast phase. If your part-time job or lower-stress role doesn’t include benefits, you’re buying coverage on the marketplace. Depending on your income, ACA subsidies may help — but this is a real budget line item that can be $500–$1,000/month for a family. Model it explicitly.

Inflation assumptions matter. The 7% figure is already inflation-adjusted, which is why we can talk about today’s dollars throughout. If you use nominal returns (like 10%), you’ll overstate your purchasing power. Stick to real returns.

This Is Permission, Not an Excuse

Coast FIRE isn’t a reason to stop building financial skills, stop thinking about tax optimization, or start treating your Roth IRA like a checking account. It’s a milestone that changes what success looks like from here on out.

Before coast FIRE: success is maximizing the savings rate and hitting the number faster.

After coast FIRE: success is finding a life you’re willing to sustain long-term, where your income covers your costs without destroying you.

Your 35-year-old self who finally hit $200k invested did something genuinely hard. The next 30 years don’t have to be. The math is on your side now. The only thing that can really wreck this is withdrawing early, making large speculative bets, or spending the next three decades panicking.

Don’t panic. Let it compound. Pick the job you can actually tolerate. The portfolio will do its job.

Your 65-year-old self is already taken care of.