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Coast FIRE is the moment when compound interest takes over and you can stop contributing to retirement. You still work to pay your current bills, but every additional retirement contribution is optional. Compound growth on what you have already saved will get you to your retirement goal on its own.
It is the most practical FIRE milestone because most people hit it 10-15 years before traditional retirement age, which fundamentally changes how you think about your career, your spending, and your time.
Your Coast FIRE number is the amount you need invested today such that, with no additional contributions, it will grow to your full retirement goal by age 65 (or your chosen retirement age).
Coast FIRE Number = Retirement Goal / (1 + r)^t
You want $1,000,000 invested by age 65. You are currently 35. That is 30 years of compound growth at 7% real return.
Coast FIRE Number = $1,000,000 / (1.07)^30 = $1,000,000 / 7.612 = $131,367
If you have $131,367 invested at age 35, you can stop contributing and it will grow to $1 million by 65 at 7% return. Anything you save after that is bonus.
Calculate your Coast FIRE number with custom inputs.
Open Compound Interest Calculator →Assuming 7% real return and retirement at 65:
| Current age | Years to grow | $500K goal | $1M goal | $2M goal |
|---|---|---|---|---|
| 25 | 40 | $33,402 | $66,805 | $133,610 |
| 30 | 35 | $46,847 | $93,693 | $187,387 |
| 35 | 30 | $65,684 | $131,367 | $262,734 |
| 40 | 25 | $92,108 | $184,217 | $368,434 |
| 45 | 20 | $129,166 | $258,331 | $516,663 |
| 50 | 15 | $181,144 | $362,288 | $724,575 |
| 55 | 10 | $254,049 | $508,098 | $1,016,196 |
The earlier you hit Coast FIRE, the smaller the number. A 25-year-old needs $66,805 invested to coast to a $1M retirement. A 45-year-old needs $258,331. A 55-year-old needs over $500,000.
Coast FIRE does not mean you stop working. You still need to cover rent, food, transportation, and current expenses. What changes:
For many people, this freedom is more valuable than reaching full FIRE earlier. The income required to live well is much lower than the income required to live well AND save 25% for retirement.
| Type | Definition | 35-year-old wanting $1M at 65 |
|---|---|---|
| Coast FIRE | Stop saving, keep working | $131,367 invested today |
| Barista FIRE | Cover essentials with part-time work | ~$300,000 + part-time income |
| Lean FIRE | Fully retire on minimal expenses | $500,000-$750,000 |
| Regular FIRE | Fully retire on comfortable expenses | $1,000,000+ |
| Fat FIRE | Fully retire with luxury | $2,500,000+ |
Coast FIRE is by far the easiest to reach. For most working professionals saving aggressively in their 20s, Coast FIRE arrives by age 35.
The 7% used above is a REAL return, meaning after inflation. If you use 10% nominal return (no inflation adjustment), you need a smaller Coast FIRE number on paper, but your goal also has to be inflation-adjusted ($1M today is worth less in 30 years).
Easier method: use real returns (5-7%) and a today-dollar goal ($1M in today's purchasing power). This automatically handles inflation.
Stricter method: use nominal returns (8-10%) and an inflated goal. For a $1M-today goal in 30 years at 3% inflation, you actually need $2.43 million in 2056 dollars. Either method gets you to the same real-purchasing-power retirement.
Open the compound interest calculator. Try different starting principal amounts with $0 monthly contribution, your real return rate (use 7%), and years until retirement. Adjust the principal until the future value equals your retirement goal. That principal is your Coast FIRE number.
Or do it directly with the formula: divide your goal by (1.07)^years-to-retirement. The math takes 10 seconds with a calculator.
Find the exact balance that lets you stop saving.
Open Compound Interest Calculator →