Coast FIRE vs. Traditional FIRE

Traditional FIRE means your investments are big enough to pay for your whole life, so work becomes optional. Coast FIRE is the earlier, smaller milestone: you’ve invested enough that the money will grow into a full retirement at a normal age without another deposit, but your paycheck still covers every bill until then.

If you’re saving toward the same retirement budget, you’ll always reach Coast FIRE first, often many years ahead. That’s why I don’t treat the two as rival strategies. Coast FIRE is the point on the way to FIRE where saving stops being mandatory, and FIRE is where working stops being mandatory.

One saver, two finish lines

Ingrid is 31 and works as a physical therapist. She has $85,000 in her 401(k) and IRA, adds $3,000 a month, and spends about $56,000 a year, which she expects to carry into retirement. Everything below uses 7% returns, 3% inflation and a 4% withdrawal rate, in today’s dollars.

For traditional FIRE she needs 25 times her spending, or $1,400,000. For Coast FIRE with a retirement age of 65, she needs $383,306 today, the amount that grows into $1,400,000 by 65 with no further contributions.

The Coast FIRE path asks for less than half the contributions and ends 12 years sooner. What it doesn’t do is free her from work. It frees her from saving.

Why is the Coast FIRE line higher by the time she gets there?

People often read their Coast FIRE number as a fixed goal. It isn’t. The $383,306 figure is what Ingrid would need if she had it today, with 34 years of growth ahead. Every year she waits, the money has one less year to compound, so the line rises.

By 41, the line has climbed to about $561K. Her contributions and growth get her past it then, but it’s worth knowing that the number the calculator shows you today is a moving target. The FIRE number doesn’t move like that. $1,400,000 stays $1,400,000 in today’s dollars whether she reaches it at 45 or 60.

What happens in the years between?

Under a pure Coast FIRE plan, Ingrid saves hard for about 10 years, then stops. From 41 to 65 she still needs to earn roughly $56,000 a year plus taxes, but she no longer needs a single dollar of surplus. She could leave a high-pressure clinic for a lower-paying job she likes more, go to four days a week, or take a year off between jobs, as long as she doesn’t touch the portfolio.

Under a traditional FIRE plan, she keeps saving $3,000 a month for about 22 years. Her life at 45 looks a lot like her life at 35. The reward comes at 53, when she can stop working entirely.

The interesting choices sit between those two. Once she’s past the Coast FIRE line, anything she keeps investing is optional, and it buys her an earlier full retirement. Here’s how that plays out if she keeps contributing after 41:

Going from nothing to $1,000 a month moves her full retirement from 65 to 59. That’s a real option for someone who wants a lighter job but not a fully relaxed savings habit. The FIRE calculator shows the full-retirement date for any monthly amount, and what to do after Coast FIRE covers the choices in more detail.

Which one should you aim for?

Aim for traditional FIRE if you want a clean exit from work and you can sustain a high savings rate for 15 to 25 years. It’s the only one of the two that lets you stop earning, and a big portfolio gives you room to handle a layoff or an illness without changing plans.

Aim for Coast FIRE if you don’t mind working, or even like it, and what bothers you is the feeling that every raise has to go straight into a retirement account. It asks far less of your savings than FIRE does, and it changes how much risk you can afford to take with your career.

It does lose its punch when it arrives late. If Ingrid saved $1,500 a month instead of $3,000, she’d reach Coast FIRE at 57 and full FIRE at 63. Coasting through the last stretch before 65 is still pleasant, but it doesn’t reshape a career the way coasting from 41 does. When the two dates are that close, I’d just plan for FIRE.

My own view is that almost everyone pursuing FIRE should know their Coast FIRE age, because it’s the first date where a bad year at work stops being a threat to retirement. After that, you can decide how much of the extra saving is worth it. If you’re choosing between a lean or a comfortable version of full FIRE, the lean FIRE comparison and fat FIRE comparison run the same kind of example at each budget.

Where this comparison breaks down

Both targets assume steady returns every year. Real markets don’t cooperate. A bad decade right after you stop contributing can push a Coast FIRE plan’s date back, and a bad decade right after you stop working is harder still, because you’re selling while prices are down. The Monte Carlo calculator shows the range.

Retiring at 53 brings problems that retiring at 65 doesn’t. Most withdrawals from retirement accounts before 59½ carry a 10% additional tax, with exceptions that include leaving your employer at 55 or later (for employer plans, not IRAs) and a series of substantially equal periodic payments. There’s also health insurance to buy until Medicare starts at 65, which our guide to coverage before 65 covers.

Neither number here counts Social Security. For Ingrid it would lower both targets, since benefits she can claim in her 60s would cover part of her spending. The Social Security version of the calculator handles that.