Coast FIRE Calculator

Calculate your Coast FIRE number

Find out how much you need invested today so compound growth alone will fund your retirement—then stop saving aggressively and enjoy life now.

Coast FIRE parameters

$
Monthly income you want in retirement
$
years
years
%
%
Using 3.9% real return (7% - 3% inflation)
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Your Coast FIRE number is $237,199 (in today's dollars). You need $187,199 more to coast. Once you reach this amount, compound growth at 3.9% real return will get you to your $900,000 FIRE goal by age 65. Save $3,426/month to reach Coast FIRE in ~5 years.

COAST FIRE NUMBER$237Ktoday's dollars
YOUR SAVINGS$50K
FIRE NUMBER$900Ktoday's dollars
PROJECTED AT 65$190Ktoday's buying power
iAll values adjusted for 3% inflation. Your savings will nominally reach $534K, but will only have $190K in today's purchasing power.

Coast to FIRE

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Your Portfolio (Coasting)
Coast FIRE Target

What does this mean?

Your Coast FIRE number ($237,199) is the amount you need invested today so that compound growth at 3.9% real return will reach your full FIRE goal of $900,000 by age 65. Once you hit this milestone, you can "coast"—stop aggressive saving and just cover your current expenses with any income.

About inflation adjustment: With 3% annual inflation, you'll nominally need $2,532,476 in 35 years to have the same purchasing power as $900,000 today. We use a real return of 3.9% (7% nominal - 3% inflation) to calculate what you truly need in today's dollars.

What is Coast FIRE?

Coast FIRE (also called Coast FI) is a financial milestone where you've saved enough that compound growth alone will grow your investments to your full retirement number—without any additional contributions. Once you reach Coast FIRE, you can "coast" to traditional retirement by simply covering your current living expenses.

The Key Insight: The earlier you reach Coast FIRE, the lower your number needs to be. A 25-year-old needs far less saved than a 45-year-old because they have more years for compound growth to work.

Coast FIRE vs Traditional FIRE

Traditional FIRE means having enough invested to retire immediately and live off your investments forever (typically 25x your annual expenses using the 4% rule). Coast FIRE is a middle ground—you're not fully financially independent yet, but you've secured your future retirement.

Traditional FIRE
Coast FIRE
Goal
Retire immediately
Retire at traditional age
After reaching
Stop working entirely
Stop saving, keep earning
Typical target
25x annual expenses
Much lower (depends on age)
Timeline
10-20+ years of intense saving
Often achievable in 5-10 years

The Coast FIRE Formula

Your Coast FIRE number depends on three factors: your full FIRE number, expected investment returns, and years until traditional retirement. The formula is:

Coast FIRE Number = FIRE Number ÷ (1 + return rate)years to retirement
Example: 900,000 ÷ (1.07)35 = 84,000

For example, if you need 1 million to retire at 65, expect 7% returns, and you're currently 30 (35 years away), your Coast FIRE number is about 94,000. That's because 94,000 growing at 7% for 35 years equals roughly 1 million.

Why Coast FIRE Appeals to Many People

  • Achievable milestone: Coast FIRE is often reachable in your 30s or early 40s, while full FIRE might take until your 50s
  • Career flexibility: Once you've "coasted," you can take a lower-paying job you love, go part-time, or start a business without risking your retirement
  • Reduced pressure: No more feeling like every dollar must go to savings—you've already secured your future
  • Better work-life balance: You can enjoy life now instead of delaying happiness until full retirement
  • Safety net: Even if your career takes an unexpected turn, your retirement is protected

What Can You Do After Reaching Coast FIRE?

Once you hit your Coast FIRE number, your only financial requirement is earning enough to cover your current living expenses. This opens up numerous possibilities:

  • Switch to a passion career that pays less but brings more fulfillment
  • Work part-time or take extended breaks between jobs
  • Start a business or freelance without the pressure of it "needing" to work
  • Take a sabbatical to travel, learn, or spend time with family
  • Volunteer or do meaningful work without worrying about income
  • Move to a lower cost-of-living area and work remotely

Understanding Inflation in Coast FIRE Calculations

One critical factor many overlook is inflation. If you need 1 million for retirement in 30 years, that million won't buy nearly as much as 1 million today. At 3% annual inflation, you'd need about 2.4 million in future dollars to have the same purchasing power.

Real vs Nominal Returns: This calculator lets you toggle between nominal returns (the raw percentage your investments grow) and real returns (growth minus inflation). Using real returns gives you a more accurate picture of your future purchasing power. A 7% nominal return with 3% inflation equals roughly 4% real return.

When "Adjust for inflation" is enabled, the calculator uses your real return rate to determine what you truly need in today's dollars. This is more conservative but more realistic—your Coast FIRE number will be higher, but it accounts for the reduced purchasing power of future dollars.

Important Considerations

While Coast FIRE is an attractive goal, keep these factors in mind:

  • Market returns vary: The 7% average return isn't guaranteed every year. Extended bear markets could delay your timeline.
  • Inflation is unpredictable: Historical average is around 3%, but it can spike significantly. Consider using a conservative estimate.
  • Keep an emergency fund: Don't count your emergency savings as part of your Coast FIRE investments.
  • Healthcare costs: If you leave a full-time job, factor in health insurance costs you'll need to cover.
  • Lifestyle creep: Your expenses today might be lower than in retirement—factor in potential increases.
Remember: Coast FIRE calculations assume you'll continue earning enough to cover living expenses. If you stop working entirely, you'll need to reach full FIRE instead.

Is Coast FIRE Right for You?

Coast FIRE works best for people who:

  • Want financial security but don't necessarily want to retire early
  • Value work-life balance and career flexibility over maximum wealth
  • Have a long runway to retirement (the younger you are, the lower your Coast number)
  • Are willing to work until traditional retirement age in some capacity

If you're driven to retire as early as possible and are willing to maintain a high savings rate, traditional FIRE might be more aligned with your goals. But if you want to reduce financial stress while still enjoying your working years, Coast FIRE offers a compelling middle path.

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