Coast FIRE: What It Is and How to Work Out Your Number
Most retirement plans assume you keep saving until the day you stop working. Coast FIRE turns that around. The idea is to save hard while you are young until your investments are large enough to grow into a full retirement fund on their own. Once you reach that point, you can stop saving for retirement entirely and only earn enough to cover today’s bills. You are not retired, but you are coasting.
The term comes from the FIRE community, short for financial independence, retire early. It appeals to people who like the freedom of FIRE but do not want to live on a tight budget for decades to reach full independence.
How the Coast FIRE number works
Your Coast FIRE number is the amount you need invested today so that, with no further contributions, it grows into your full retirement number by your chosen retirement age. It depends on three things: the full target you need at retirement, the number of years until then, and the return you expect.
The formula is the full target divided by the growth factor over those years. If you need $1,000,000 at 65 and expect 5% a year after inflation, $1 today becomes about $1.05 to the power of the years left. At age 35, that is 30 years and a growth factor of about 4.3, so your Coast FIRE number is roughly $231,000.
Coast FIRE numbers by age
The table shows how much you need invested at each age to coast to $1,000,000 in today’s money by 65.
| Your age now | At 5% real return | At 4% real return |
|---|---|---|
| 25 | $142,000 | $208,000 |
| 30 | $181,000 | $253,000 |
| 35 | $231,000 | $308,000 |
| 40 | $295,000 | $375,000 |
| 45 | $377,000 | $456,000 |
Because these figures use returns after inflation, the $1,000,000 at 65 means $1,000,000 of today’s buying power. Using 5% real is close to the long-run history of a stock-heavy portfolio, while 4% leaves more room for a weaker few decades.
If your full target is bigger, scale up. Someone who needs $1.5 million at 65 has a Coast FIRE number of about $272,000 at 30, $347,000 at 35 and $443,000 at 40 at a 5% real return.
Finding your full target first
Coast FIRE only works if you know where you are coasting to. Start with the yearly spending you expect in retirement, subtract the Social Security or pension you expect, and multiply what is left by 25 under the 4% rule. If you expect to spend $55,000 a year and receive $25,000 from Social Security, your savings need to cover $30,000, so your full target is $750,000. The FIRE number calculator does this step for you.
What life after Coast FIRE looks like
Once you hit the number, the money you were putting into retirement accounts is free. Some people use that to switch to lower-paid work they enjoy more, go part-time, take a long break between jobs or start a business with less pressure. The only rule is that your income must keep covering your living costs, because touching the invested pot would break the plan.
This is close to Barista FIRE, where part-time work covers some costs in early retirement while investments cover the rest. The difference is timing: Coast FIRE is about stopping saving, Barista FIRE about starting to draw down. The Barista FIRE calculator handles that version.
The risks to keep in mind
Coast FIRE leans heavily on returns over a long period, so a poor couple of decades in markets can leave you short. Building in a margin helps: use a lower return, aim a little above your number, or keep contributing a small amount after you reach it. It is also worth checking your progress every few years and saving again for a while if markets have lagged.
The other risk is lifestyle creep. If your spending in retirement turns out higher than planned, your target was too low. Revisit your full target whenever your life changes in a big way, such as having children or moving to a more expensive area.
Work out your own number
Enter your age, planned retirement age, target and expected return in the Coast FIRE calculator to see your number and how far you are from it. Like every projection here, it is a planning estimate and not financial advice, but it gives you a clear milestone to aim for.
Run your own numbers
This guide is general information for planning, not personal financial advice. Figures were checked on the date shown and can change.