What Is Coast FIRE? A Simple Explanation
Coast FIRE means you’ve already saved enough that, without adding another dollar, your investments will grow into a full retirement by the time you need it. Here’s how it works and how to find your number.
By Bogdan · Updated
Coast FIRE is a milestone on the road to retirement. You reach it when the money you’ve already invested is enough to grow — on its own, with no more savings — into everything you’ll need to retire at your chosen age.
After that point, you still need to earn enough to pay today’s bills. But you can stop saving for retirement, which might mean taking a lower-paying job you enjoy more, working fewer hours, or spending more now.
Explain it like I’m 5
Imagine planting a tree. When it’s tiny, you have to water it every day. But once it’s big enough, its roots find water by themselves — it keeps growing even if you stop watering it.
Your investments work the same way. Early on, you have to keep adding money. Once you have “enough”, the growth from compound interest carries you the rest of the way. That point is Coast FIRE: you can stop pushing and just coast.
Find your own number with the Coast FIRE calculator — it shows whether you’re already there and when you will be.
The Coast FIRE formula
It takes two steps.
Step 1 — your FIRE number (how much you need at retirement):
FIRE number = yearly spending in retirement ÷ withdrawal rate
With the common 4% withdrawal rate, that’s the same as spending × 25. Spending $40,000 a year means a FIRE number of $1,000,000.
Step 2 — your Coast FIRE number (how much you need today):
Coast FIRE number = FIRE number ÷ (1 + real return) ^ years until retirement
The real return is your investment return after inflation — for example a 7% return with 2% inflation is roughly 5%. Using it keeps every number in today’s dollars.
Coast FIRE numbers by age
How much you’d need invested today to have $1,000,000 (in today’s money) at age 60, assuming a 5% real return:
| Your age today | Years to grow | Coast FIRE number |
|---|---|---|
| 25 | 35 | $181,290 |
| 30 | 30 | $231,377 |
| 35 | 25 | $295,303 |
| 40 | 20 | $376,889 |
| 45 | 15 | $481,017 |
Notice how fast the number climbs: a 45-year-old needs more than 2½ times as much as a 25-year-old for the same goal. That’s why the early years of saving matter most. For tables covering retirement at 55 or 65 and different spending levels, see Coast FIRE number by age.
Coast FIRE vs. other types of FIRE
| Type | What it means |
|---|---|
| FIRE | Your investments fully cover your spending — work becomes optional now. |
| Coast FIRE | Your investments will cover retirement later; you work to cover today’s bills. |
| Barista FIRE | Investments cover part of your spending now; a part-time job covers the rest. |
| Lean FIRE | FIRE on a small budget (often under ~$40,000 a year). |
| Fat FIRE | FIRE with a large budget and plenty of cushion. |
Things that can go wrong
- Returns may be lower than you assume. A 5% real return is a common estimate, not a promise. Using 4% instead raises the number noticeably.
- Your spending may grow. Children, a bigger house or health costs can raise what you need.
- Fees and taxes reduce your real return. A 1% fee takes a big bite over 30 years.
- The money has to stay invested. Coasting only works if you don’t spend the pot along the way.
Many people treat Coast FIRE as a “safe to slow down” point rather than a reason to stop saving entirely — even small extra savings make the plan much sturdier.
Frequently asked questions
What does Coast FIRE mean?
Coast FIRE means your retirement investments are already big enough that they’ll grow into the amount you need by your retirement age, even if you never add another dollar. You still work to pay your current bills, but you no longer need to save for retirement.
How do I calculate my Coast FIRE number?
First find your FIRE number: yearly retirement spending ÷ your withdrawal rate (for example $40,000 ÷ 4% = $1,000,000). Then divide it by (1 + real return) raised to the years until retirement. With 30 years to go and a 5% real return: $1,000,000 ÷ 1.05^30 ≈ $231,000.
What is a good Coast FIRE number at 30?
It depends on how much you’ll spend in retirement. To have $1,000,000 in today’s dollars at 60, assuming a 5% return after inflation, you’d need about $231,000 invested at 30. Someone planning to spend less needs less.
What is the difference between Coast FIRE and Barista FIRE?
With Coast FIRE your savings cover your future retirement but you still earn enough to pay today’s bills. Barista FIRE means you’ve saved enough to partly live off your investments now, and a part-time job covers the rest (and often health insurance).
Is Coast FIRE realistic?
It’s one of the most reachable FIRE goals, especially if you start investing young, because time does most of the work. The risks are lower-than-expected returns, higher spending later, and stopping saving too early — so many people keep saving a little as a safety margin.
This article is for general education and is not financial, investment or tax advice. Rates, rules and limits change; check current terms with your bank or the IRS. See our disclaimer.